DIGEST 2006

2

Considerable effort has been taken to ensure the accuracy andreliability of the information contained in this publication. However,neither Sabita nor any of its members can accept any responsibilitywhatever for any loss, damage or injury resulting from the use orimplementation of this information.

The views and opinions expressed in this publication are those of theauthors, and do not necessarily reflect the views of Sabita or any ofits members.

Sabita Digest

Published by the Southern African Bitumen Association

5 Lonsdale Building

Lonsdale Way

Pinelands 7405

South Africa

Tel. +27 21 531 2718

Fax. +27 21 531 2606

email info@sabita.co.za

www.sabita.co.za

March 2007

ISBN 978-1-874968-32-0

Information from this publication may be reproducedprovided the source is acknowledged

Vision

Mission

3

Sabita’s plans and actions are consistent with good corporatecitizenship to underpin its dealings with government, and toassist its members.

Sabita will:

• advance best practice in southern Africa with due regard to worker health and safety, as well as the conservation of the environment;

• provide education and training schemes to develop skillsand competencies that are sustainable and aligned tonational goals and frameworks; and

• engage government to promote the social and economicvalue of road provision and efficient delivery by state roadorganisations.

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Contents

Foreword . . . . . . . . . . . . . . . . . . . . . 7

1. Valediction

Local and international accolades mark retirement ofPiet Myburgh . . . . . . . . . . . . . . . . . . . . 11

2. Industry Overview

Bitumen, gravel and the fuel price in South Africa . . . . . . . . 17

Prof Don Ross

Aggregate supply to the road construction sector . . . . . . . 28Alex Weideman

Health and safety in the workplace . . . . . . . . . . . . 30Piet Myburgh

3. Education and Training Updating best practice guidelines and documents . . . . . . . 39Trevor Distin

SA's education system: A systematic overhaul is vital to sustainable skills acquisition . . . . . . . . . . . . . 45Prof Emile Horak

Improving service delivery through appropriate road maintenance . . . . . . . . . . . . . . . . . . 61Mike Winfield

SAT: 2006 activities generate a new vision of member service . . . . . . . . . . . . . . . . . . . 64John Onraët

Flexible pavement engineering course to cater for industry needs . . . . . . . . . . . . . . . . . . . 67Les Sampson

4. Innovation

The use of steel slag aggregate in asphalt mixes . . . . . . . 73Hugh Thompson, Michael Bouwmeester

In search of sustainable pavement solutions . . . . . . . . . 82Prof Kim Jenkins, Dr Fritz Jooste

Overcoming temperature and time constraints using FT wax . . . . . . . . . . . . . . . . . . . . 88Francois Bornmann, Robbie Hiley, Stefan Strydom

Advantages of SA's new single pass surface dressing machine . . 96Deon Pagel

Innovative design methods for HMA in Gauteng . . . . . . . 102Derick Pretorius, Herman Marais

Forensic investigation into premature distress in asphalt . . . . 111Elzbieta Sadzik

5. Best Practice

Old habits die hard ... especially in Cape Town . . . . . . . 119Julian Wise

Disposal of penetration grade bitumen in South Africa . . . . . 126Mannie Levin

Bond and tack coats to improve total structural integrity . . . . . . . . . . . . . . . . . 130Kobus Louw

A performance classification system for SA: Quo Vadis? . . . . 138Prof Kim Jenkins

The use of modified binders in road construction in SA . . . . . 143Dennis Rossmann

Developments in seal design . . . . . . . . . . . . . . 147Gerrie van Zyl

The influence of weather on prime applications . . . . . . . 150Johan Muller

The development of a Road Transport Management System in SA . . . . . . . . . . . . . . . . . . . . . . 159Paul Nordengen

Accreditation of thin bituminous surfacings in SA . . . . . . . 166John Odhiambo

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Foreword

7

We are proud to bring you the 2007 digest publication. Great effort hasbeen made to ensure that we cover a wide spectrum of topical andrelevant issues, ranging from the latest developments in producttechnology to socio-economic issues which all have a bearing on thedesign and use of bituminous materials. This is an industry publicationsupported by local practitioners, and we are very grateful for thecontributions made by those authors who have generously shared theirtime, knowledge and expertise.

The intention of the Digest has always been to offer practitioners avehicle through which they can provide an insight into newdevelopments which could impact and shape the future of our industry.We trust that we have achieved this and that readers will gain a newunderstanding of the current status of our industry, and be encouragedto embrace innovation and implement new developments within yourown organisations.

The construction industry in South Africa is experiencing unprecedentedgrowth after many years of under spending on infrastructure provisionand preservation. This changed scenario presents a new set ofchallenges to our resource base, with a resultant increase in demand forskills and materials. Some of the articles written provide insight intothese problems, and a vision of how some of the challenges are beingaddressed. For ease of reading the articles have been grouped into foursections namely: Industry Overview, Education and Training,Innovation and lastly Best Practice.

We trust that you will enjoy reading this edition of the Digest and find itas enlightening and interesting as previous editions.

Trevor DistinCEO

Sabita

1

Valediction

Piet Myburgh, inter-nationally acknowledgedas an authoritative and

influential leader in bituminous technology in the southernhemisphere, retired asexecutive director of theassociation in September2006, after more than twodecades of distinguishedservice.

Myburgh took office as executivedirector of Sabita in October 1981, when the association was justemerging from its fledgling years.He leaves behind him a bodywhich today stands alongside itssister bodies throughout the world as an equal. He will, however,continue to offer his knowledgeand expertise to Sabita in aconsultant capacity.

His retirement was officiallymarked at a gathering of currentand former Sabita councillors inCape Town, where incumbentchairman Phillip Hechter paidtribute to Myburgh's contributionto the asphalt sector in particular,and to the southern African region in general.

"While never losing sight ofSabita's primary obligation topromote the interests of itsmembers, Myburgh built a deeperand broader agenda into hisleadership, ensuring that theasphalt sector maintained its

pivotal role in the social andeconomic development of thesouthern African region,” Hechtersaid.

"In doing so, he earned inter-national respect as a thoroughstrategist, whose technicalexpertise, and comprehensiveunderstanding of the political andeconomic changes taking placeduring his tenure, fostered theevolution of a healthy, robust andflourishing asphalt sector.

As an engineer for the CapeProvincial Roads Department for17 years, Myburgh developed aunique broad-picture under-standing of the technologicaldemands of a good road network,the importance of its maintenanceand management, and of theimportance of such a network to

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Local and internationalaccolades mark retirement ofPiet Myburgh

Piet Myburgh was awarded lifemembership of Sabita at his

retirement function in September 2006

economic growth. In addition tostructural design of roadpavements and the formulation oflaboratory testing specifications,he was responsible for thedevelopment and implementationof judgment of complianceschemes based on probabilitytheory, the conception andimplementation of a pavementmanagement system for the entire trunk route system for the CapeProvince, and identifying researchneeds in the field of pavementengineering.

This experience laidthe groundwork foran unequalledoverview of thesymbiotic andintegratedrelationship betweenthe bituminousproducts industry and the roadinfrastructure systemit serves. Hisappointment briefwas comprehensiveand laid the foundation forSabita's expansion into newstrategic territories that wouldexpand the association's pivotalrole in the growth anddevelopment of South Africa 'sbituminous products sector.

In 1984 Sabita took the helm asthe secretariat for CAPSA, whichwas launched in 1969 to satisfythe unique technological,economic and social demands ofthe southern African region. Under Myburgh's guidance CAPSA rapidly attained international stature,attracting global authorities onevery aspect of blacktop pavement

engineering, including technologydevelopment, infrastructuremanagement, human resourceprovision, and the safety ofworkers and the environment.

The evolution of CAPSA over thisperiod facilitated the cross-pollination of local andinternational technology, fosteringthe emergence of a knowledgeable industry able to match inter-national standards ofinfrastructure design and

construction.

CAPSA remainspivotal to Sabita'sfar wider focus onthe transfer ofknowledge at alllevels. To meetthis need Myburgh motivated theestablishment ofthe AsphaltAcademy (AsAc)in 2001, and theacademy's regis-tration in 2002

initiated the evolution of SouthAfrica most authoritative focus for the education and training needsof the bituminous products sector.

Providing a wide range of servicesfrom courses and workshops tothe publication of best practiceguidelines, AsAc, which took overthe CAPSA secretariat in 2004, has established itself as an integralarm of the industry.

Further focussing on the transferof knowledge, Myburgh was also a driving force in the publication ofSabita's widely respectedtechnical manual/guideline series

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... an unequalled

overview of

the relationship

between the

bituminous

products industry

and the road

infrastructure

system it serves.

and audio-visual training aids, and was instrumental in the launchingof the Road Pavements Forum(RPF) in 2001 to replace theBituminous Materials LiaisonCommittee (BMLC).

AREST

Sabita's Asphalt Research Strategy (AREST) programme, which hasevolved through four separatephases, was initiated by Myburghin 1988, in association with theCSIR. Established todetermine the asphalt research needs ofboth the public andprivate sectors on ajoint and interactivebasis, the ARESTTask Force was, andremains, Myburgh'sbrainchild, and hasdelivered significantbenefits in the formof greater efficiencyin establishing andmaintaining acost-effective roadnetwork on the sub-continent.

He was also responsible forestablishing the bituminousproducts industry's mostprestigious and sought-afterincentive award, the SabitaExcellence Award, which is nowpresented annually. The first suchaward was made in 1988.

He also initiated socialdevelopment programmes such as the Councillor EmpowermentProgramme to promoteinfrastructure delivery at localgovernment level, Sabita'sInfrastructure Development

Assessment Programme (SIDAP)under Professor Don Ross todevelop a more productive method for evaluating rural road needsand to foster a closer synergybetween blacktop engineering andeconomic priorities. He alsodirected the formation of Sabita's Centre for Occupational Safety,Health and EnvironmentalConservation (COSHEC) tofacilitate the implementation ofglobal standards of worker safetyand environmental preservation.

Throughout histenure with Sabita Myburgh flew theSabita flag atinternationalconferences,keeping up withinternationaldevelopments and setting uplong-standingassociations withworld leaders inbituminousproducts

engineering. These remain inforce, and have proved invaluablein ensuring the maintenance ofglobal standards in South Africa'sroads industry.

Contributions

Hechter noted that recognition ofMyburgh's contributions have been plentiful over the years, includingtwo made at the celebration ofSabita's 25th anniversary duringCAPSA'04 at Sun City. Guestspeaker Professor Steve Brown ofNottingham University said Sabitawas able to stand alongside NAPA, EAPA, AAPA and Eurobitume as

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Myburgh earned

international

respect as a

thorough

strategist, and

fostered the

evolution of a

robust asphalt

sector

one of the world leading tradeorganisations in the field of flexible pavement engineering.

He quoted from Brown address:

"While Sabita's success isundoubtedly the result of a teameffort, I must nevertheless paytribute to one person whosesteady hand on the tiller has beena vital ingredient in its success, aman who has provided continuityof leadership through difficulttimes. I refer, of course, to PietMyburgh, who has appreciatedboth the technical and socio-economic requirements of Sabita members, and has led yourorganisation with distinction."

In a message of congratulation atthe same function Ray Farrelly,chief executive officer of AAPA,said his organisation, “and indeed

the world asphalt community, has benefited from the friendshipand cooperation afforded bySabita, by Piet Myburgh, and bythe many others who have beenpart of Sabita over its 25-yearjourney."

Myburgh's ongoing associationwith Sabita will include involve-ment in CAPSA'07, during whichhe will act as HSE sessionchairman and provide generalmanagement inputs. He will also review reports and manageinputs for existing technologydevelopment projects i.e. bitumenstabilised materials, hot mixasphalt wearing courses and HiMAtrial sections, and will assist withupdating existing Sabita manualsand writing articles for publications such as the Sabita Digest, AsphaltNews and trade publications. q

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2

IndustryOverview

Four fifths of SA’s roads(ex clud ing ac cess roads)are un sur faced. While this

is not high by gen eral Af ri canstan dards, it is more than wefind in coun tries with perca pita GDPs sim i lar to ours.

There are strong economicreasons for thinking that many ofthese roads should be upgraded to a bituminous pavement, at leastamong those made with gravelrather than in situ soil. The samereasons argue against buildingnew roads according to principlesthat preserve the current ratio ofbitumen to gravel, or tip it furtherin favour of gravel. Simply put, ahigher proportion of new roads we lay down should be bitumen-surfaced.

This remains true despitesignificant increases in the price of bitumen, driven by the generalspike in the cost of petroleumproducts, since early 2005.Certainly, these increases havestressed road budgets. TheGauteng Department of PublicTransport, Roads and Works

reported in 2005 that the cost ofupgrading a gravel road to a lowvolume sealed road had increasedby 67% since 2004, and the costof upgrading to a standardsurfaced road had increased by48% in the same period. Thisobviously implies that fewer roadscan be upgraded or built fromscratch without increased budgetallocations, or until substantialnew efficiencies can somehow befound.

Paved vs gravel roads

However, this obvious point should not be confused, as it often is,with the idea that construction and maintenance of paved roads hasbecome significantly moreexpensive relative to properlymaintained gravel roads. It isoften assumed that becausebitumen is a petroleum product, itmust inevitably become arelatively worse option comparedto gravel and cement when theworld oil price is elevated.

This reasoning leads to theconclusion that the proportion of

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Choosing road surfaces:

Bitumen, gravel and the fuelprice in South Africa

Don Ross

Professor, School of EconomicsUniversity of Cape Town

and University of Alabama

unsurfaced roads we shouldupgrade and the proportion of new surfaced roads – as opposed tothe totals that can be affordedfrom a fixed budget – should bothbe reduced from what theyotherwise would be.

In this article, I will explain whythis hasty reasoning is mistakenfrom an economic point of view. If we slow the pace of roadconstruction and upgrading as aresponse to more expensive fuel,this should mainly mean fewergravel roads rather than fewersur faced ones. (Note that re duc ing main te nance out lays on ex ist ingroads of ei ther type to save money would be self-de feat ing, sincede fer ring this ex pen di turein creases to tal costs, and theworld price of fuel is not ex pectedto de cline soon enough, if it everwill, to offset this fact.)

Around the world, a standingsupposition prevailed for manyyears that urban streets andprovincial and national highwaysshould be paved, and that thedefault materials for all otherroads should be soil and gravel.Gradually over the past decade ortwo, however, a moresophisticated understanding of the value of infrastructure assets hasoverturned the traditional view.Before turning to the issue of theimpact of fuel price increases, Iwill review the economicarguments for paving roads atlower levels of expected trafficvolume than was once generallyaccepted.

The basic business of economics is opportunity-cost calculation.

Whenever a decision or policyleads to a stream of benefits andcosts, we can attempt to evaluateit in terms of other possiblestreams we could have hadinstead if we’d made analternative decision about how todispose of our resources (including money, but also time andadministrative energy).

Thus, in considering the relativevalues of bitumen and gravelroads, we compare the costs andbenefits of one type of road withan estimate of those we wouldhave if we’d invested the samemoney, materials and planning ina road of the other type.

Shadow pricing

In the case of public infra-structure, benefits accrue oversome period of time. If periodicmaintenance of an asset isrequired, as with roads, then thesame is true for some portion ofthe costs. The moment we set outto estimate opportunity costs over time, we must discount futurevalues by the difference we attach between having the benefits orpaying the costs now anddeferring them.

A com mon ap proach where money is con cerned is to set the dis countrate by ref er ence to the dif fer encebe tween the in ter est rate earnedby a safe fi nan cial as set and theex pected me dium-term rate ofinflation.

In SA it is currently customary tobenchmark this at 8%. There arethen two ways (which shouldagree with one another) in which

18

we can economically test apossible investment:

• The discount rate capturesthe opportunity cost ofcapital. In a soundinvestment, this must be less than the discount rate atwhich the present value ofbenefits and costs are equal,i.e. the internal rate of return (IRR).

• We subtract the discountedcosts from the discountedbenefits so as toestimate the netpresent value(NPV) of thecontemplatedinvestment. This is the mostdirect way ofcomparing twotypes orinstances ofasset, such as agravel road anda paved road:which has thehigher NPV? It is immediately obvious that this form of comparison must behighly sensitive to the periodof time over which we choose to estimate costs andbenefits. One asset might pile up costs earlier than anotherbut then deliver a better ratio of benefits to costs at laterstages. How many of theselater stages are factored intothe calculation of NPV willthen crucially influence theconclusion of our comparison.

The key to effective economicanalysis of any investmentdecision is finding a way to

account for all consequences thathave value to people or imposecosts on them, even where thevalues and costs in question don’thave prices assigned to themdirectly by markets. Suchnon-traded cost and benefitstreams must be assignedso-called ‘shadow prices’, that is,monetary amounts people appearwilling to pay to avoid the costsand acquire the benefits.

For example, if someone whosetime can be soldon the consultingmarket for R1,000 per hour spendstwo hours permonth polishingtheir car, we canshadow price thevalue of a shinycar to that personat R24,000 peryear.

Bearing in mindthat surfacedroads are

relatively costly to build butrelatively cheaper to maintain than gravel roads, we can identify thetwo general factors that havemainly contributed to over-estimations of the economic valueof gravel roads as compared topaved ones. The first is failure toconsider long enough periods incalculating NPVs, or implicitlyassuming too steep a discountrate (which amounts to the samething). The second is failure toincorporate shadow prices for arange of non-traded benefits thatflow from paved but not fromgravel roads, or flow from gravelroads only to a lesser extent.

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The key to

effective economic

analysis ... is

finding a way to

account for all

consequences that

have value to

people or impose

costs on them

These two issues are directlyrelated: most of the importantshadow-priced benefits frompavements accrue gradually.

Before turning to these, however,let us start with costs. In southern Africa the construction cost of akilometre of surfaced road with aregular chip seal is, on average,about 2.4 times the cost ofbuilding a properly engineeredgravel road. Maintenance of afull-scale paved road constructedwith hot mix asphalt costs, onaverage, 1.9% per year of initialconstruction costs until the pointat which replenishment of thewearing course is necessary.

Maintenance costs/km

Maintenance of a gravel roadcosts, on average, 27% of initialconstruction costs until the pointat which regravelling is necessary. These averages conceal thedifferent effects of traffic volumeson the two types of road. A recentstudy in the US state of Minnesota found that gravel roadmaintenance costs per kilometrerise significantly at two thresholds: by 9% at an average annual dailytraffic (AADT) rate of 50, and by30% at an AADT of 200. This isalso the point at which gravelmaintenance costs shootdramatically past bitumenmaintenance costs, with the gapthereafter widening steadily withAADT.

Gravel roads must be regravelledon a shorter cycle than thatassociated with bitumen roadresurfacing. This has a doubleeffect on NPV comparisons: first, if

we choose a long enough period itwill include more regravelings than bitumen resurfacings, and,second, we will calculate the costof the first regravelling operationin less steeply discounted Randbecause it arises closer to thepresent.

In southern Africa, bitumenresurfacing is half as costly onaverage as regravelling if roadsare adequately maintained duringthe intervals. The fact that thissmaller number gets multiplied bya smaller discount factor becauseof the earlier date to regravel adds to the strength of the relative case for bitumen.

Nevertheless, use of the propor-tional relations above as the solebasis for trying to determine when a paved road is more economically efficient than a gravel roadproduces a relatively conservativethreshold for upgrading.Differences stemming from AADTrates dominate all other factors on this skimpy information base.

Conservative

As a result, one would concludethat paving is only justified whereAADT is expected to pass 200.Even adopting this conservativenumber would lead to upgrading,if budget allowed, of about 40% of current gravel road kilometres inGauteng, for instance. (Gauteng is not claimed to be representative.Its large population pushes up itsAADT levels compared to otherprovinces). On the other hand, itssmaller distances push down itsrelative proportion of inherited,and possibly inefficient, unpaved

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roads. These considerationsinfluence the optimal upgradingquotient in opposite directions, but there is no reason to suppose thatthey neatly cancel each other out.)

In any case, this conservativeconclusion arises only prior toconsidering other relevant benefits of paved surfaces and costs ofgravel ones. Before we turn to the domains where shadow pricing isconcerned, one direct financialcost factor, which can’t yet bequantified because it is speculative but will turn up on public books as a market price rather than ashadow price, must be taken intoaccount. This is that new gravel isbecoming scarce in SA, so its price is sure to rise.

Municipalities are nolonger allowed toopen new pits without performingenvironmental impact assessments, whichare beyond theresource capacity ofmost ruralauthorities. Inaddition, in manyin stances in south ernAf rica, op ti malma te ri als for gravelroads are con cen trated un derar a ble land that has higherop por tu nity value as farm landthan as gravel. Thus, on the ba sisof con struc tion and main te nancecosts alone, we should ex pect thethresh old for sur fac ing, what everad di tional con sid er ations we useto determine it, to drop in SA.

However, as noted, accounting forthese costs is only the beginning

of economic analysis. Let us nowconsider the shadow-pricedbenefits of road surfacing thatshould also be factored intoevaluation.

• Because of the dust theyspread onto crops, wildlifeand people, gravel roadsimpose heavierenvironmental costs thansurfaced ones. Dust causesallergies and respiratoryillness, especially in smallchildren. People must cleantheir homes, businesses andvehicles more often in dustyconditions, and this is not acost that should be ignoredsimply because it is not borne

by the state. Itis, after all, still borne by thecountry on thedimension thatultimatelycounts formost, viz.,reducedproductivity.Even seemingly trivial expenses can producehigh overallcosts whenmultiplied by

enough people and hours incalculating aggregate shadow prices. To my knowledge, noone has ever tried toestimate the costs of roaddust in any jurisdiction. Thetask would be quitedemanding. It is surely worth doing, however, because theresulting magnitude might be surprising to many, and thusmight in turn help people not

21

Municipalities

are no longer

allowed to open

new pits without

performing

environmental

impact

assessments

to forget a hidden cost ofgravel roads;

• Rougher road surfacesincrease vehicle operatingcosts, especially fuel use andtyre wear. Fuel use premiums on gravel roads are especially noteworthy if one of theconsiderations leading somepeople to worry aboutbitumen use is its upwardinfluence on our consumption of petroleum products. A1991 CSIR study estimatesthat equivalent trafficvolumes burn, on average,6% to 7% more fuel ongravel roads than on pavedones. Though this alreadyrepresents a very substantialcost externality for gravel,Namibia’s Klaus Dierkses ti mates a higher fig ure of20%. This partly re flectsDierks’s re stric tion to verylow-qual ity gravel roads.How ever, the shadow pricehere is clearly high on anyac count. Us ing South Af ri candata, Dierks sum ma risesover all ex tra ve hi cleop er at ing cost dif fer ences onme dium-grade gravel roads(IRI = 8) as com pared tome dium-grade sur faced roads (IRI = 4) at a low end of19% for buses and 27.5% for me dium-weight trucks. Hisover all con clu sion, based on a mix of Namibian and SouthAf ri can data, is that merelyfac tor ing ve hi cle op er at ingcosts into the com par a tiveeco nomic eval u a tion of roadtypes re duces the re gionalthresh old AADT for sur fac inga gravel road to be tween 120

and 160. (On his cal cu la tion,up grad ing to full as phaltpave ment does not move thethresh old from my ear lieres ti ma tion of 200.) If thethresh old of 120 wereadopted in Gauteng, thiswould re sult in 50% of gravel road kilometres beingregarded as warrantingupgrade;

Safer roads

• Paved roads are safer thangravel roads because onpaved surfaces vehicles canbrake to faster stops fromequivalent speeds and areless disposed to skidding.According to the CaterpillarPerformance Handbook, thecoefficient of traction (theratio of horizontal force thatwould cause tyres to move to the vertical force on the tyre) for rubber tyres on a surfaced road is 0.90, as opposed to0.36 on unsealed gravel. This is offset somewhat by thefact that vehicles tend totravel faster on surfacedroads. However, accidentdata save us from having tospeculate about the relativestrengths of these counter-vailing influences. First, a1998 study by CSIRTransportek concludes thatroad surface conditionscontribute to about 8.6% ofall accidents in SA, and thatsurface improvements wouldprevent 10% of thesealtogether – so, 0.86% of the total. The accident rate permillion vehicle kilometres ongravel roads is more than

22

double that for two-lanesurfaced roads, and thecomposition of fatalitiesamong accidents on gravel(10.9%) is higher than on2-lane paved roads (7.8%),and much higher than onfull-speed freeways (3.2%).Thus effects of differences invehicle control stronglyappear to swamp differencesin driving speed whereaccident harm is concerned;

• Gravel roadscannot, likebituminous ones, be constructedand maintainedentirely usingsmall equipment that can beoperated byunskilled people; thus they fail to take intoaccount SA’s abundance ofunderutilised labour, and areless effective at developinghuman capital in smallcontractors. NationalGovernment’s ExtendedPublic Works Programme(EPWP) mandates thatwherever labour-intensivemethods can be deployed forthe same budget outlay ascapital-intensive methods,the former should befavoured. In fact this is tooconservative, using anaccounting measure of valuewhere an economic measurewould be more appropriate.Use of small contractors inroad construction andmaintenance builds humancapital in the form ofmanagement, tendering and

investment skills, with theacquisition of manuallyoperated surfacing equipment an additional benefit. Sincesuch capital is an economicasset with future multipliers,we should not implicitly setour willingness to invest in itat zero, as the EPWPpresently does.

It is unfortunately not possiblehere to attempt a quantitative

estimate of thehuman capitalinvestment valueaccruing tosurfaced roadconstruction andmaintenance overgravel roadconstruction andmaintenance. Theissue has been

confused in many discussions bybenchmarking targets of ‘numbers of jobs’.

Unlike human capital, ‘jobs’ arenot assets since they are functions of overall productivity in theeconomy, are not fixed in extent,and do not have opportunity costsin the strict sense.

Over the coming year, I and mygraduate students at UCT hope tomake progress against thisconfusion and produce a firstquantitative estimate of thepotential value in human capitalcreation of labour-intensiveroadwork. In the meantime, wemust be content with noting thatwhatever effect this has on theshadow price of gravel, thedirection of the influence is clearand must further reduce the

23

.... capital is

an economic

asset with

future

multipliers

threshold for paving from the160/120 benchmark arrived atabove.

Similar remarks are in orderconcerning the othershadow-priceable factorsdiscussed above and not yetquantitatively estimated in amodel, viz., environmentalimpacts and safety. We saw earlier that the previous benchmarkwould direct us to upgrade 50% of gravel road kilometres in Gauteng. Consideration of the factorsawaiting shadow pricing must then increase this already ambitiousthreshold, probably substantially.

The influence of the fuelprice

Now that the factors affecting therelative economic values of pavedand gravel roads have beenidentified, we can consider the

relevance of fuel price increases to the balance of these factors.

For most of the past six years, the price of gravel has risen fasterthan real in fla tion in SA, whilebi tu men price in creases have been sub-in fla tion ary. How ever,bi tu men prices be gan ris ing fasterthan in fla tion about one year ago. Fig ures 1 and 2, com piled fromdata re leased by Sta tis tics SA,show these relationships:

Suppose – as may or may not bethe case – that 2005 is the firstyear in a secular trend withrespect to these pricerelationships. This tells us nothingabout whether the change inrelative prices is enough tosignificantly offset theconsiderations raised abovefavouring increase in theproportion of surfaced roads.Several considerations suggest

that it is not.

First, theargumentspresentedaboveemphasisethat gravel’srelative costs tend to behidden unless IRR, NPV and opportunitycost arecalculatedover anappropriately extendedtime period.If weresponded tothe 2005/6

24

Figure 1 (Source StatsSA)

relativefluctuation by increasing our proportion ofgravel used,at a pointwhere thesupply ofdomesticgravel isfacing newconstraints,this can onlypush up theexpected cost of gravel.

Secondly –and muchmoreimportantly – basicmaterials are far from the largestcost component of either surfacedor gravel roads. In the case ofbitumen roads, costs of labour,plant, investigation, design, roadmarking, signage and other inputs make up a minimum of 75% oftotal construction andmaintenance costs.

Labour intensive methods

With the exception of plant theseadditional inputs are mainlydomestically produced – and tothe extent that we increaseemphasis on labour-intensivemethods, machinery can beincreasingly domestically sourcedas well. By contrast, the largestcost component by far inconstruction and maintenance ofgravel roads is haulage associatedwith the replacement of lostwearing course gravel. Gravel isheavy. It is most often carried in

trucks. Trucks run on petroleum(diesel) fuel. This expenditure,unlike increased expenditure onbitumen, occurs beyond the firstyear of a road project. Thus theproportional impact of rising fuelprices on road construction costsgoes steadily upward for gravelrelative to bitumen as timehorizons are extended. To theextent that rising fuel prices areexpected to be a negative external shock on road budgets, theirproportionate impact is greaterthan on surfaced road prices given the use of the discount rateemployed for most publicinvestment purposes.

Third, because the proportion ofgravel road cost inflators (dieselfuel and heavy machinery) thatmust be imported are higher thanfor surfaced roads, factoringexchange rate risks intocomparative NPV calculations also

25

Figure 2 (Source StatsSA)

lowers the optimal proportion ofgravel.

For maintenance of SA’s currentextent of gravel roads, we requireabout 30 million cubic metres ofgravel to be hauled each year. Atcurrent distances between borrowpits, this is costing about 30million litres of fuel. An additional10 million litres of fuel is used forblading by motor graders. Thisamounts to about 0.1% of total SA diesel fuel consumption. Thesefigures must be expected to risefaster than the fuel price if ouroverall use of gravel for roadsincreases.

Environmental issues

As environmental considerationsreduce the acceptability of opening new borrow pits, as opposed toincreasing the sizes of a reducednumber of pits, average haulagedistances must increase. Datacollected from South-East Asiaindicate that for every additional10 km. that gravel must behauled, costs increase by $2 percubic metre.

By contrast, since the majority ofinputs to a bitumen road are notimported, then to the extent thatSA’s pavement materials inflationis driven by world prices, overallcosts of surfaced roads should beexpected to be sub-inflationary.

These considerations can hardlybe said to show anything decisiveat this point. They surely should,however, block any casualsuggestion that high fuel pricesshould imply more gravel roadspending completion and testing ofa full quantitative estimation ofinput-output functions in SA’s road industry.

The arguments mustered heresuggest that were we to respondto the increased fuel price byreducing our use of bitumen forroads in favour of gravel, wewould likely find that after 7-10years we had reduced rather thanenhanced the overall efficiency ofour road network compared towhat we could have had for thesame net investment.

While it is true that we cannotbuild or maintain as manykilometres of roads per Rand asearlier in the decade (at least,given current productivity), it isprobably not true that if budgetsare not increased andretrenchments are made theseshould first be applied to newsurfaced road construction or toupgrades from gravel. Rather, theopposite is more likely.

By early 2008, we aim to haveproduced an economic model inwhich these speculations can berigorously tested. q

26

Wideranging questionshave been raisedabout the ability of the

aggregate industry to meetincreased demand in the roadconstruction industry –questions which cannot beexamined without reflecting on the past.

The aggregate industry is part ofthe construction industry, whichwent through a long period of lowdemand, starting in the mideighties. This causeda number of plants to be shut down ormothballed, andothers were forced torationalise if theywere to stay inbusiness, andminimal investmentin existing and newplants took place.With the suddenunprecedentedgrowth in the market over the last two years, shortages in certainproducts have been experienced.

Admittedly, there has been a lot of talk about the shortfall of materialsupply, and the aggregateindustry has invested significantfunds in recent years in therefurbishment and upgrading ofexisting plants. In addition, a large number of mobile plants that could help alleviate the shortage ofmaterials have been imported, but there are concerns that some ofthese plants may be used innon-regulated mining areas.

Rest assured, theaggregateindustry doeshave more thanenough reservesto cope with theincreaseddemand. Mostcommercialoperations have at least a 10-yearmining plan. Inthe short-term

certain operators might have toinvest in their quarries to open the mine up for good quality material,but no shortage should beexperienced.

28

Optimising resource utilisation:

Aggregate supply to the roadconstruction sector

Alex Weideman

Product Technical ManagerHolcim SA (Pty) Ltd

The aggregate

industry has

more than

enough reserves

to cope with

the increased

demand

It is interesting to note that roadsurface material has higherspecification requirements whencompared with the balance ofconstruction industry products,and that it makes up only a smallpercentage of the total aggregatemarket demand. Not all sources of aggregate type are thus suitablefor use as road surfacing stone.

Specifications

Quarries that produce to thesespecifications invest in technicalexpertise, screening and crushingequipment, and put a great deal of effort into complying with thesespecifications. The day-to-dayproduction of standard stoneproducts does not always complywith the stringent road surfacingspecification, and it is usuallynecessary for this material toundergo additional screening andcrushing if it is to comply.

The remainder of the materialscreened off during this processoften does not fall within anyspecification which results inaggregate suppliers generating“waste stockpiles” that are difficult to market.

In addition, production yield of the aggregate sizes required for roadsurfacing are often the slowest tocome off the plant. The demandon road surfacing contracts usually arises over a very shortpeak period in the year, whichcould cause suppliers to overcommit to orders, resulting in ashortage of material during thecontract. Fortunately, with thelatest crushing technology, it hasbecome easier to produce to these

specifications. However not allaggregate producers are in aposition to upgrade their plants tothis standard.

It is important to stress thataggregate producers are workingvery hard to produce to thesestandards and trying their levelbest to keep up with the currentdemand. This objective would bemore easily achieved if specifiersof road stone material were moresensitive to the realities of whatcan be delivered from a crushingplant. Without this kind of mutualunderstanding, shortages inspecific sizes are inevitable.Specifiers and suppliers need towork together to avoid thisproblem becoming a reality, andengineers are encouraged toascertain from the quarries whataggregates are available beforedeciding on the type of surfacingto be used in their design.

Optimisation

This would lead to betteroptimisation of the stone yieldfrom the quarry, and therebyreduce the generation of unusablematerials. In the event of wantingto utilise high performancesurfacings it is imperative that the engineer predetermines whatthe inherent properties of the local aggregates are in terms ofkey performance parameters such as polished stone value (PSV) and the quarry’s ability to produce the required average leastdimension (ALD). The latterinformation is crucial to ensurethat the industry continues toprovide sustainable best valueproducts to our clients. q

29

The year 2007 will see arenewed commitment onthe part of Sabita to a

comprehensive business planto advance global best practice in health, safety andenvironmental conservation(HSE) in South Africa. Tangible outputs have and will continue to be pursued to advance andsupport members’ initiatives to implement these HSE norms.

Thus, ultimately, Sabita willrepresent a membership that isinformed on current global bestpractice and future developmentsthat impact on SA, a membershipthat voluntarily adopts methodsand procedures compliant withglobal norms, leading to an ethosof self-regulation within theindustry.

Crucial to the attainment of thisgoal in the medium term is theinstitution of safety performanceassessment schemes and,subsequently, award programmesthat publicly acknowledge thosemembers who commit to theprinciples of corporate

responsibility to their employeesand the environment.

Commitment

This year saw a significantincrease in the dedicated fundingof the business plan formulatedwithin the context of the COSHECstrategic cluster, with the backingof the sponsor members (the oilcompanies). This enhancedresource will enable Sabita tolaunch an industry drive congruent with the oil companies’ commit-ment to putting profitabilityside-by-side with obligations toworker wellness and sustainablepractice that protects the fragileenvironment.

Key to the execution of the plan isto give downstream industry every encouragement and assistance toadopt triple bottom line policiesthat include:

• the development of trainingmaterial and programmesfocusing on safety in theworkplace; and

30

COSHEC in 2007:

Health and safety in theworkplace – walking the talk

Piet Myburgh

• the establishment ofprocesses and activitiesaimed at bringing global bestpractice to their doorstep.

Consistent with a shift in emphasis from operational objectives in thepast to strategic objectives in thefuture, Sabita will canvassmembers’ representatives atmanagement level to serve on theCOSHEC strategic cluster focusgroup. In such a manner theknowledge, experience andleadership capacity within theindustry will be mobilised to giveimpetus to the execution of theplan.

Business plan

The scope of the activities of theCOSHEC business plan iscomprehensive, and covers allproducts and services normallyprovided by the bituminousproduct industry. Thus, in the case of the handling of bituminousbinders, it is envisaged that all the following phases of handling willbe taken into account in thedevelopment of appropriate codesof practice and trainingprogrammes:

• Loading of product atrefineries or depots;

• Transportation, particularlyby road;

• Off-loading at storagefacilities at secondaryindustry establishments;

• Storage and handling atmanufacturing site, factory or construction site;

• On-processing or valueaddition operations e.g.emulsification, modification;

• Waste management whendisposing of surplus product.

The scope of workplace activitiesassociated with the servicesprovided by the bituminousproduct industry will include:

• Binder application to the road by spraying as well aschipping operations;

• Hot mix and cold mix asphaltmanufacture;

• Transporting of asphalt;• Application i.e. paving and

compaction;• Milling;• Crack sealing;• Sampling and laboratory

testing;• Traffic accommodation during

construction, maintenanceand rehabilitation operations;

• General site hygiene;• Waste management i.e. the

disposal of excess asphalt ormilled materials.

Global standards

As part of its goal to advance thelevel of awareness of global norms and standards through thedissemination of best practice, aninitiative aimed at promoting thediscontinuation of the use of coaltar products in road constructionwas launched recently with thepublication of Sabita Manual 26 –Interim guidelines for primes andstone precoating fluids.

Including input from the Societyfor Asphalt Technology (SAT)following a series of seminars held nationally, the guideline highlightsconventional wisdom on alter-natives to coal tar products, and is

31

designed to assist road authoritiesin the selection of provensubstitutes for carcinogenic andenvironmentally aggressive coaltar products. The guideline focuses on priming granular bases andprecoating surfacing stone, and isintended to serve as an interimguideline until documents such asthe outdated TRH1: Prime coatsand bituminous curing membranes (1986) have been updated.

Despite Sabita’swide-rangingawareness campaign, and the lead taken by the South AfricanNational RoadsAgency Limited(SANRAL), theProvincial CouncilWestern Cape andthe GautengDepartment of PublicTransport, Roads and Works, none of South Africa’s 248 municipalities nor anyof the six metropolitan councilshave yet undertaken to prohibitthe use of coal tar products intheir road infrastructure projects.

This is a problem demandingincisive action, as it isinconceivable that professionalengineers should continue to allow environmentally harmful andunhealthy products to be specified for road construction when thereis widespread substitution of thisproduct with alternatives that areless harmful to workers or theenvironment.

Another initiative to advance theintroduction of global norms andstandards in South Africa is the

introduction of the first plenarysession, Health, Safety and theEnvironment (HSE), at CAPSA’07this year. This session, convenedwithin the context of the COSHECbusiness plan, will havedistinguished speakers fromEurope and the USA presentingup-to-date papers on topicscovering legislation on theregistration, evaluation andassessment of chemical

substances, thechallenges facedand dealt with bythe asphaltindustry in bothEurope and theUSA to meet theneeds of society in respect of HSE,and futureindustrial trendsto ensure thatprocesses aresustainable andappropriate to

reduced reliance on non-renewable energy resources.

Workplace safety

To mitigate employee exposure toinjury or ill-health arising from the handling of bituminous products,Sabita recently launched abitumen safety course, whichkicked off in June 2006 when 25employees from membercompanies took part in the BitSafe train-the-trainers courses inStellenbosch, Johannesburg andDurban. These trainers will nowhead up comprehensive trainingcourses at their own companies toentrench awareness of the hazards associated with the handling ofbituminous binders, and to

32

No

municipalities

have yet

undertaken

to prohibit

the use of

coal tar

products

mitigate the risks of exposure tothese hazards.

The modular format of the coursefacilitates training while limitingimpact on production, and theintention is that all employeesinvolved with the handling ofbitumen throughout the supplychain should complete all 13modules within a two-year period.The course and its associatedawareness-building function issupported with the design andpublication of a series of safetyposters which are now beingissued free of charge to Sabitamembers. These posters aredesigned to be displayed in areasmost frequently encountered byworkers engaged in the relevantactivities by encouraging workersto protect themselves againstinjury by wearing of PersonalProtective Equipment (PPE).

Trainers will have the support oftraining aids such as DVDs,training manuals, prepared slidepresentations and posters.Trainees will be assessed at theconclusion of each module, andwill receive a joint Sabita/Asphalt

Academy certificate on completionof the course.

Guidelines Started in 2006 and currentlyunderway are steps to reviseSabita Manual 23 – Bitumenhauliers’ code: guidelines forloading bitumen at refineries. It iscommon cause that the relevanceand comprehensiveness of thispublication have been overtakenby time, and hence a project waslaunched to correct this situation.The purpose of the project is tocompile a nationally accepted code of practice for loading bitumen atrefineries, and the following stepswill be followed towards this goal:

• Identify shortcomings of thecurrent haulier code;

• Liaise with marketers/refiners to supplement content;

• Revise and procureagreement;

• Liaise with transportindustry;

• Collate comments and reviseaccordingly;

33

Bitumen safety posters

Sabita's BitSafe DVD

• Obtain endorsement andcommitment from refiners;

• Publish and market.The project has now reachedPhase 2, and visits to all refineriesare underway to elicit concernsand proposals for a uniform codeof entry, loading and exit of bulkbitumen haulers at refineries inSouth Africa.

Review

A review of thecurrent documentpoints to a number of issues that wouldneed to be addressed in preparation of theproposed review.Some of the principal ones are listed below:

• The currentdocument relieson the willingcompliance ofSabita membersand hauliers forits successful implement-ation. This somewhatindulgent approach is notwhat is envisaged in theCOSHEC business plan, andconsequently it is likely thatthe title of the new document will be: A national code ofpractice for loading bitumenat refineries in SA, with thecontent phrased accordingly.It is envisaged that thepreface to the document willcarry an endorsement by allprimary producers (i.e.marketers and refineries) and an undertaking to enforce the content at their loading sites;

• The current document admits to variance of standardsand/or procedures atrefineries. The aim is to adopt a single (minimum) nationalstandard code thatadequately addresses safetyand environmental issues.Should any particular refinery have additional requirements, these can be dealt with in anappendix (or the Sabita

website) thatcan beamended fromtime to time.

Operations

Operationalaspects that willbe coveredcomprehensivelyare:

• Entryprocedures;

• The vehicle(roadworthy

certificates, pre-loadinspection, dangerous goodsplacards, orange box etc);

• The driver (Medical fitness EC license and PrDP(DG)qualifications and declarationof compliance etc.);

• Requisite documentation(uplift documentation,dangerous goods declarations etc., MSDS);

• Required loading proceduresto be followed by the haulierdriver and assistant as wellas refinery staff;

• Departure procedures.

Since publication of the currentdocument in 2000, attitudes and

34

The aim is

to adopt

a single

(minimum)

national

standard code

to address safety

and environmental

issues

policies with regard to HSE havechanged significantly, and refinery standards and requirements forload upliftment have converged.As a result the content of themanual will be substantiallyamended during the revision.Cognisance will also be taken ofSabita Manual 25: Qualitymanagement in the handling andtransport of bituminous binders,which contains awealth ofinformation thatneeds to beincorporated inthe proposedcode. Ultimately it maybe necessary tocompile acomprehensivedocumentcovering theattainment of both the safety andquality standardsin the handling ofbitumen fromrefinery tosite/depot. Thiswill obviate the obvious pitfalls ofduplication and discrepancies, andthose associated with periodicupdates.

Safety file

Sabita has compiled a Safety Fileto assist those members involvedin the construction of bituminoussurfacings and layer works in thecompilation of a Contract SafetyFile as stipulated in the OHS act.The main section of the guiderecommends risk assessment andsafe work procedures for a rangeof operations and plant directly

related to the handling ofbituminous materials. Examplesare also given of a typical safetymanagement structure and theappointment and responsibilities of safety management positions interms of the OHS Act. Thisdocument has been published inthe Members Only section of theSabita website for editing by ourmembers as they see fit.

Waste disposal

A full report on thecurrent status ofpublic-privatesector interaction to facilitate thepermitting of sitesfor the disposal ofsurplus bitumen can be found on Page126).

Memberparticipation

Ultimately, COSHEC will succeed in its

goal if its vision “...to incentivisemembers to adopt a culture ofcorporate responsibility in respectof sustainable work practices,worker safety and environmentalprotection” materialises throughvoluntary participation.

Fundamental to achieving this goal is the establishment of a reference framework or criteria for theassessment of members’performance which, as a first step, can be measured against simplecriteria such as:

• a commitment to the non-use of coal tar products;

35

Sabita's guide for in-servicesafety training

• institution of Sabita safetytraining programmes;

• disposal of surplus bitumen to approved landfill sites only;

• acceptance only of bitumenconsignments that have been loaded in accordance withrefinery safety requirements;and

• submission of incident reports for incorporation into anational incident database for establishing a nationalindustry benchmark.

Eventually members’ performancewill be assessed against national

norms and compliance withlegislation relevant to theirindustrial operations. It isenvisaged that membersperforming well against criteriacurrently being developed shouldbe appropriately rewarded through a prestigious annual industryaward scheme.

Such members will in themselvesbecome the industry beacons, forothers to emulate on theascendant road to achievingprofitability through safe andresponsible means. q

36

3

Education and

Training

Notwithstanding variousapproaches to theNational Department of

Transport (NDoT) by bothSabita and the RoadPavements Forum, culminating in a briefing by Sabita of theMinister of Transport, JeffRadebe in November 2005,national documents that aresupposed to reflect bestpractice for the design,construction and maintenanceof roads continue to languishin a state of obsolescence.

This inability on the part of NDoTto respond to a well articulatednational need could possibly beascribed to the irreversiblemigration of institutionalknowledge to the SA NationalRoads Agency Ltd (SANRAL) whenthat body was established in 1998.

Sabita has always held the viewthat these documents, such as the series of Technical Recommend-ations for Highways (TRH), andTechnical Methods for Highways(TMH) and national specifications,

form the basis of soundengineering practice aimed at theoptimal provision and maintenance of our road network. A furtherbenefit is that these documentscan provide an essentialspringboard for new entrants intothe roads industry, whereby theycan avail themselves of thebenefits of decades of experienceand achievement in the roadsindustry.

Incisive action

Given the crucial role of up-to-date codes of practice andspecifications in ensuring thesustainability of the road buildingindustry and to stem the erosionof skills from the various roadauthorities at both provincial andmunicipal levels, incisive corrective action needs to be taken byappropriate industry sectors toredress the shortcomings.

Sabita has responded to this needby significantly increasing itsinvestment in technologydevelopment in the bituminous

39

Towards an informed industry:

Updating best practiceguidelines and documents

Trevor Distin

Chief Executive OfficerSabita

product sector, an initiativedesigned to ensure that a wellinformed bituminous materialsindustry is sustained through thesystematic publication of updatedand current best practiceguidelines.

Standard test methods

The standard test methods forroad building materials arecontained in TMH 1, which waslast updated in 1986. Many ofthese methods arenow outdated andneed to bereviewed. TheMaterials TestingCommittee of COTO is currentlyreviewing selectedTMH 1 test methods to bring them intoline with legislatedaccredited systemrequirements. Therevised testmethods willtherefore be rewritten andpublished as national standardsunder the auspices of the SABS.

Sabita has agreed to finance therevision of the test methodspertaining to bituminous products. This will be a mammoth task, buta vital one if we want to ensurethat reliable and accurate testmethods are in place to measureand control the quality of ourproducts. This initiative has thestrong support of Sabita’smembership, as it allows theprivate sector to have direct inputinto the review process underSABS from which they werepreviously excluded.

During the course of 2007 theasphalt test methods will berevised, and Dave Wright ofNinham Shand (Pty) Ltd has beenappointed to facilitate the processbetween industry and SABS.Thereafter we intend tostandardise the modified bindertest methods which are currentlycontained in the AsphaltAcademy’s (AsAc) TG1 document.Fortunately the test methodsspecified in SABS specifications for penetration bitumen, cutback

bitumen andbitumen emulsionsare based oninternational testmethods such asASTM, which areregularly reviewedand thereforeup-to-date.

Best practiceguidelines

Over the yearsSabita has been

committed to the publication ofbest practice guidelines to keepthe industry at large informed onnew developments in bituminousproduct technology, and toconsolidate best practice. Many ofthese publications are beingovertaken by new technology,products and procedures, and arein need of review. This reviewprocess will include an increasedfocus on the safe handling aspects of bituminous products and theimpact of their usage on theenvironment. The medium of technologytransfer has also evolved fromhard (printed) to electronicformat. However, electronic

40

Sabita has

responded to

industry needs by

significantly

increasing its

investment in

technology

development

versions of some of Sabita’s earlier manuals do not exist. Sabita hasrecognised this and will beupdating selected manuals andalso re-shooting its video testingseries onto DVD format. Theseefforts have received a furtherboost from CAPSA,which has allocated aportion of its surplusfunds towards theupdating of Sabitamanuals and audiovisual aids. Below is asummary of the current status of the reviewprocess now underwayon selected Sabitamanuals and audiovisuals:

Manual 2 – Bituminousbinders for roadconstruction andmaintenance: Thefourth edition of thismanual is currently under reviewand has been expanded toincorporate information on theconstitution and rheology ofbitumen. The manual containsupdated information onspecifications, testingand HSE issues forbinders.

Manual 5 – Guidelinesfor the manufactureand construction of hot mix asphalt: An expertgroup has beenappointed to review the contents of the manual with the purpose ofincorporating the latest developments in HMAmanufacture and

paving into the second edition.

Manual 10 – Appropriatestandards for bituminoussurfacings: An inception study has been done to determine the scopeof work required to update this

manual. A proposal isbeing considered tofinance further research into incorporating latest developments onlabour basedtechniques for theconstruction andmaintenance of lowvolume roads.

Manual 16 – Economicanalysis of short termrehabilitation (REACT):A decision has beentaken to finance theupgrading of theoriginal REACT program from a DOS to Windows

operating system, ultimately forincorporation into the revisedTRH12 which is being funded bySANRAL. This software is a vitaltool for analysing the impact oftimely pavement maintenance and

rehabilitation at aproject level.

Manual 19 – Technicalguidelines for thespecification and design of bitumen rubberasphalt wearingcourses: The secondedition has alreadybeen reviewed and isawaiting finalisation ofthe TG1 specificationfor bitumen rubberbinders before going toprint.

41

Manual 22: Hot mixpaving in adverse

weather

Manual 2: Bituminousbinders for roadconstruction and

maintenance.

Manual 22 – Hot mix paving inadverse weather: This manual has already been revised and thesecond edition was published inAugust 2006. The first edition hasbeen expanded to capture broader experiences outside the WesternCape and to formulate practicalrecommendations for paving in awide range of conditions applicable to the southern Africanenvironment.

Manual 23 – Bitumen haulier’scode: This manual will be reviewed with the intent to develop astandard practice for loadingbitumen at refineries. It will beexpanded to incorporate, interalia, driver training and vehiclerequirements to facilitateimproved safety awareness. Thisinitiative will be funded out of thededicated COSHEC budget forHSE.

Manual 26 – Interim guidelines for primes and stone precoatingfluids: This manual serves as aguideline to capture best practicein the replacement of coal tarbased products forpriming bases andprecoating roadsurfacing stone. Thisnew publication wasdistributed inNovember 2006 and its purpose is to assistroad authorities withthe selection of provenalternative productsand processes. Thispublication was alsofinanced out of thededicated COSHECbudget for HSE.

Video series

Sabita has 15 videos covering thetesting of penetration bitumen,bitumen emulsion, bitumen rubber and hot mix asphalt. The plan is to begin by filming the penetration,cutback and emulsions tests, asthese are based on internationaltest methods, and to film theasphalt and modified binder testsonly once these have beenreformatted under SANS.

New manuals

Sabita's commitment to aninformed industry is not limited toonly updating existing publica-tions, but also to identify gaps inthe coverage of best practice andto fill these. To this end three newmanuals have been identified forpublication in the near future.

They are:

Manual 27 – Design and use ofslurry seals: A request was tabledat the November 2006 RoadPavements Forum (RPF) for the

industry to capture best practice in the designand use of slurry. Some information iscontained in thecurrent TRH3 document on the design of seals,but the intention is toremove this information from the new TRH3.The new document willpresent correcttechniques andprocedures for thedesign and applicationof slurry in a widerrange of applications

42

Manual 26: Interimguidelines for primesand stone precoating

fluids

from texture treatments tooverlays, slurry bound Macadams,Cape Seals, microsurfacing and rut filling.

Manual 28 –Acceptance criteria for the design and use of thin layerasphalt (ACTLA): The purpose ofthis manual is to encapsulate thefindings from research carried outon developing protocols for thedesign and quality control of thinlayer asphalt wearing courses. Itis aimed at the use ofthin layer HMA on lowvolume roads such asthose in residentialareas, where theenvironmentalconditions differ fromthose of highways.

Manual 29 –Certification of binderdistributors: A draftguideline, intended toreplace TRH1 has been compiledon the requirements for certifyinga binder distributor for sprayingbinders to. The publication of thismanual, replacing TRH 1, will take place as soon as the new bindercalibration system involving theoutsourcing of the certificationprocess to a third party isimplemented by the provinces.

Dissemination

The intention is that all these newmanuals will be available on theSabita website, www.sabita.co.zain PDF format at no cost. Similarlythe electronic copies of thesemanuals will be placed on CDs fordistribution at no cost to

engineering students atuniversities and universities oftechnology. Hard copies will stillbe printed and sold to coverpublication costs.

All these efforts in updating bestpractice publications are aimed atpartnering with government andassisting, where, possible, withthe transfer of knowledge to newentrants into the industry. Ourefforts are further augmented

through ourassociation with theAsphalt Academy(AsAc) and the Society for Asphalt Technology (SAT). Both AsAc andSAT are instrumentalin disseminating information throughseminars andworkshops. AsAc'straining courses areaimed at educating

practitioners on the latesttechnology in the blacktopindustry, while SAT hostsworkshops where information isshared and debated with itsmembers on new technologicaldevelopments.

AsAc also captures best practicethrough the publication ofmanuals, known as TechnicalGuidelines (TG), which have thewider input of all stakeholders inthe roads industry. The RPF TaskGroup on modified binders iscurrently reviewing the technicalguidelines on The use of modifiedbituminous binders in roadconstruction (TG1) and the second edition is expected to be published in April.

43

Students' CD

Conclusion

There is much concern in theindustry about the lack ofcommitment from CentralGovernment for the NDoT to takecustodianship of updating nationalstandards and codes of practicefor road building materials. Sabitais very much committed toensuring that those documents,which have an major influence on

the performance of bituminousproducts, are up to date andreflect current best practice. Every effort will be made to achieve thisobjective, and we welcome theopportunity of partnering withroad authorities and agencies inour endeavours to ensure that our technology remains competitive,and that we have a well informedindustry. q

44

One of the realisationsSouth Africa hasexperienced since 1994

is that the welcome to theinternational scene had asweet as well as a bitter side.The sweet side was theobvious miracle of democracyand all it brought to all ourpeople. The down-side ofdemocracy is that it alsobrings internationalcompetitiveness to your door,together with a lot of bitterlessons.

Michael Porter (1990) studied theinternational competitiveness ofnations, and he found that thequality of education, andparticularly that in science, mathsand technology, is one of the main underlying factors influencing thesuccess of a nation in such aglobally competitive situation.

Lawless (2005), in her study ontrends and figures in the civilengineering profession in SouthAfrica, showed that for bothmedical and all engineering

professionals in SA, the ratio ofpopulation to professionals wasbetween 2000-2500:1 while forfirst world countries it rangesbetween 100-500:1. This disparity in benchmarking with thedeveloped world can be furtherverified in Figure 1 (see followingpage), which shows the results ofa recent study (Fricke et al, 2006)of the ratio of persons of the24-year old population per country qualified in Science andEngineering (S&E).

This clearly shows that SouthAfrica is not even the leader inAfrica, and extremely weak whenbenchmarked against Japan, theUK or the Nordic countries. Theuse of 24-year olds also implies alonger term impact, as it ispersons of that age, with the rightskills and qualifications, who willsustain any competitive positionover the next 10 to 15 years.

The recent economic growth in SAhas been spectacular by allstandards, but the realisation thatsustainability may become an

45

South Africa's education system:

A systemic overhaul is vital tosustainable skills acquisition

Emile Horak

Professor and Head of Departmentof Civil Engineering

and Biosystems EngineeringUniversity of Pretoria

issue has also grown in govern-ment circles. Government has putforward a R372-billion five-yearpublic infrastructure investmentprogramme to address thissustainability problem. Thisinvestment is seen as key fordriving higher levels of economicgrowth required to achieve SouthAfrica’s broader aim of halvingpoverty and unemployment by2014 (Le Roux, 2006). Theshortage of suitably qualifiedtechnical people has beenidentified as the most importantobstacle to the sustainability ofthe government’s economicmiracle over the longer term, and

also to the implementation of itspublic infrastructure investmentplan.

The Accelerated and SharedGrowth Initiative for South Africa(ASGISA) developed bygovernment identified six bindingconstraints which must beovercome. “Besides the shortageof suitably skilled labour, theseconstraints entail the volatility and level of the currency; the cost,efficiency and capacity of thenational logistics system; barriersto entry, limits to competition andlimited new investmentopportunities; the regulatory

46

Figure 1. International benchmarking of science and engineering populations

environment and red tape onsmall and medium–sizedbusinesses; and deficiencies inState organisation, capacity andleadership” (Le Roux, 2006).

The Joint Initiative on PrioritySkills Acquisition (JIPSA) hassubsequently been launched tocounter the skillsdearth of engineers, artisans and othertechnically skilledpeople who will beessential in makingASGISA work.

JIPSA was launched on March 27 2006by Deputy President PhumzileMlambo-Ngcuka asa multi-stakeholdergroup in whichgovernment,business and labour have joined forcesto fast-track the provision ofpriority skills for accelerated andshared growth.

These include high-level,world-class engineering andplanning skills for core networkindustries, such as transport,communications and energy.Other critical skills on the list are:

• city, urban and regionalplanning and engineeringskills;

• artisan and technical skills,particularly, those needed for infrastructure development;

• management and planning ineducation, health andmunicipalities;

• teacher training formathematics, science,information andcommunication technology(ICT); and

• language competence inpublic education. (Le Roux,2006).

JIPSA hassubsequently set“rough” targets forSouth Africa’suniversities anduniversities oftechnology. Theymust increase thenumber ofengineeringgraduates by a total of 1000 graduatesper year. Secondly,the country’suniversities oftechnology mustincrease thenumber of

technologists they produce by 300 a year. Thirdly the number ofqualifying artisans must beincreased to between 15 000 and20 000 a year. (Le Roux, 2006).

An amount of R48 million hasimmediately been made availableto give support to engineeringfaculties to achieve these targets.Unfortunately “correctingformulas” used in the pastprevailed in the current fundingallocation to universities, resultingin institutions like the University of Stellenbosch receiving nothingbecause their student demog-raphics are not satisfactory. Thistendency to persist with politicaladjustment motives ignores thereality of the limited capacities at

47

JIPSA targets call

for engineering

graduates to

increase by 1000

per year;

technologists by

300 per year; and

artisans by 15 000

to 20 000

per year

these universities, even if they are politically corrected, and seems tomisjudge the problem definition.

Even though the Deputy Presidenthas frequently noted that JIPSAshould not be seen as a “silverbullet” it seems that there is some confusion with the just in time(JIT) concept. There seems to be a lack of understanding that suchtargets cannot be set or producedwithout understanding the systemthat must be in place to supportsuch outcomes.

The systemic nature of the defects in the education systemunderlying the ambitious targetsset by JIPSA iseither ignored, orsuffers from thetypical SouthAfrican politicalattitude – which isto issue decreesand presume theproblem is thussolved. JIPSAseems ignorant ofthe bigger picture of the currentaggressiveinternationalcompetition for thesame scarce technical skills. Withthe best of nationalistic intentions, like the “welcome homerevolution”, there may not evenbe short term gains of possiblyattracting some of the “drainedbrains”. There is a systemicproblem in the education systemin South Africa which is at thebottom of the skills developmentpyramid, and this needs to berecognised and addressed before

there will be any real sustainableskills development. This paper will concentrate on thesystemic problems in theeducation system by unpackingexperience gained from asuccessful maths and scienceoutreach program todisadvantaged schools over thepast 3 to 4 years. It will also show that these problems would need to be addressed in a systematicfashion and that longer term goals will have to be set and not justshort term politically motivatedsocial engineering goals.

Root of the problem

Applying the Paretoprinciple to thefactors identified by ASGISA, it isevident that theroot of the problemis the consistentlylow number oflearners with maths and science atschool level. This isclearly alsoconfirmation of thefactors alreadyidentified by Porter(1990). National

South African matriculation figures show that the number ofmatriculants has steadily declinedfrom about 550 000 in 1998 toabout 450 000 in 2003 as shownin Figure 2. Even though this trend has bottomed out, the furtherproportional aspects, such asthose passing with exemption, are still disturbingly low.

Approximately 12% of thesematric entrants wrote maths on

48

There is a systemic

problem in the

education system

in South Africa....

which must be

addressed before

there will be any

sustainable skills

development

the standard grade while only 4%wrote maths on the higher grade.The same disturbing trends wereobserved for science matricresults. The Third InternationalMathematics and Science Study(TIMSS) in 1994/1995 andTIMSS-R (repeat survey in 1999)confirmed that South Africanlearners are consistently weak inmaths and science at the Grade 8level, compared with the otherinternational participants. (Howie,1999 and 2002). A media releaseby the HSRC (December 2004) onresults of the TIMSS 2003 studystated “Comparison with TIMSS1999 indicates there was nosignificant difference inmathematics and science scores in this period”.

This international benchmarkingexercise is used even bydeveloped countries, like the USA,

as a strong indicator and tool tolocate problems in their educationsystem (Horak and Fricke, 2002).In the case of SA, the consistentlylow performance clearly points tosystemic problems in theeducation system. Among themany factors contributing to thelow performance of these learnersis the negative attitude and lack of competence of teachers: “On thewhole, about half of the teachersreported feeling ill-prepared toteach the content of eithermathematics or science curricula.There appears to be few teacherswith significant experience and arelatively small percentage haveuniversity level qualifications”(Howie, 1999).

Whilst there are many otherinterventions attempting toaddress these or similar issues,many of them tend to be

49

Figure 2. Matric result trends

“quick-fix” solutions, offeringsupport rendered to learnersalready in their matric year. These interventions cannot bring aboutreal sustainable change, and often cannot initiate deep change as the learners’ foundations are alreadypoor or they have already beencommitted to maths and sciencestudy on the standard grade. Inaddition, although the combinedaffect of numerous interventionstrategies in education havebrought about generally improvedpass and matriculation exemptionrates, the number of learnerswriting maths in matric hasdecreased, and while thepercentage of learners passing onthe Standard Grade has increased, this percentage has remained atbetween 4% and 5% for HigherGrade learners.(Taylor, Muller &Vinjevold, 2003,12).

TeacherMentorshipProgramme(TMP)

Anecdotal evidenceindicates thatmathematicsteachers promotestandard grade mathematics as ithas a higher pass rate potentialand higher symbol potential thanhigher grade mathematics. Thisrelates to the way in which theirperformance is being measured,too. Parents are often alsoignorant about the longer termimplications for career choices.(Fricke and Horak, 2006).

The maths and science teacherswere identified by the University of Pretoria as the most cost effectivearea of involvement for theengineering industry in improvingthe numbers and quality of mathsand science learners (Horak, 2003and Horak and Fricke, 2004). Toaddress the maths and sciencecrisis, a pilot project was started in 2004 in five disadvantaged schools concentrating on teacher supportand capacity building.

The Teacher MentorshipProgramme (TMP) involvesindividual mentoring of teachers of mathematics and science in grade8 to 12, during timetabled freeperiods in school time, byexperienced mentor teachers onthe school premises. Such

interventions aredesigned to takeplace once in every7-day cycle for atleast a 3 yearperiod to ensuresustainability.

Workingconditions

Research andexperience haveshown that shortcourses and

workshops away from their ownwork environment proliferate, buthave limited lasting effect as itoften ignores the reality of theteachers’ working conditions andthe problems they face (Fricke etal, 2006). This on-site involve-ment is therefore to ensureteachers are empowered toaddress all aspects of their

50

The TMP has

highlighted

teachers'

utter confusion

with the

Outcomes Based

Education

(OBE) system

professional work, within thecontext of their work environment.

The teacher mentoring in thisinitiative is supported by acomprehensive programme, forboth teachers and learners, ofexposure to Science, Technology,Engineering and Maths (STEM)and awareness of careers in theSTEM industry (Horak and Fricke,2004). A particular objective is the improved qualifications of thematriculants, in the hope thatmany more of them will enter theengineering fields. In the rest ofthis paper the observations fromthis TMP intervention will bedescribed to illustrate the fullimpact and implication on the total system of skills development which it must feed into (Fricke etal, 2006 and Fricke/Horak, 2006).

The TMP project has been runningfor 22 months in five schools, andthere are many positive indicatorsof progress. However, thefollowing observations, made atthe start of TMP interaction withthe schools, indicate that there are systemic problems in the schoolswhich impact on the maths andscience achievements of learners. Some of these comments arebased on personal observations,but external audits done byeducation experts were also usedto provide a more objective view.

Even though these observationsmay appear to be highlightingnegative aspects, it is designed toconfirm the systemic nature of the problem and many of theproblems have seen improvementin the last twenty months.

In general, the experiences withteachers during the first year ofTMP implementation hashighlighted their (Howie, 2002),utter confusion with the outcomesbased education (OBE)methodology introduced in recentyears, and general incompetencein the various forms ofassessment.

Qualifications

Consider the qualifications of theteachers at five TMP secondaryschools 2004 as shown in Table 1:

However, this number of teachersat the secondary school level must be looked at in more detail.

Experience and observation(Howie, 2002) has shown thatthese teachers are NOT qualifiedfor the post they are in, and this is partly because:

• Many are not teaching thesubject for which theyobtained their qualifications;

• Most received diplomas atteaching colleges which were

51

Total number ofteachers

Qualified to teach atprimary school level

Qualified to teach atsecondary school level

50 16 34

Table 1: Teacher qualifications

phased out subsequent to the change of government in1994, and in many cases thequality or standard of thediplomas is questionable;

• Some of the teachers laststudied the subject that theyare teaching during their own school years.

These have the followingconsequences:

• Lack of subject contentknowledge and confidenceleading to incorrect teaching;

• Lack of appreciation of theneed for sequencing ofteaching content, leading to a lack of structure andplanning;

• An inability to exploreconcepts with learners, as the teachers do not understandthe concepts themselves.

Teachers’ skills

In the recent analysis of nation-wide surveys amongst learners inthe Numbers and Needs study byLawless (2005), it was found thatlearners reported that they arebeing taught by:

• Under-qualified teachers;• Teachers who do not

complete the syllabus;• Teachers who cannot give

adequate explanations;• Teachers who do not mark or

check their work.

A deeper analysis of these aspects at the TMP schools confirms thefollowing points:

• Syllabus completion/teaching pace: No properplanning takes place, hencethe teaching pace is often fartoo slow, leading to syllabinot being completed. In ananonymous questionnaire,32% teachers said that theywould bring the learners induring the holidays tocomplete the syllabus, ratherthan pace themselves tocomplete it during term time;

• Focus on seniors: Manyteachers do not see theimportance of getting theyounger learners to finish the syllabus to provide theknowledge base for thefuture;

• Minimal use of teachingtime: An estimate based onon-site observations by thementors show that learnersreceive only about 35% ofthe allocated period time;

• Teaching style: Teachersare not generally interactivewith learners, norstimulating, possibly becausethey have no confidence withthe material. Teacher talkdominates most of theclassroom time;

• Homework: Teachers do not give enough homework andare unable to enforce it being done;

• Science laboratorypracticals: most teachershave never done laboratorywork themselves, either atschool or at college, andtherefore they do not conduct experiments at school.

52

Assessing

Teachers are often unclear on how to assess and cannot differentiatebetween different types ofassessment. As a result of poorEnglish proficiency, they strugglein setting assessments in whichlearners understand what they are required to do. Theiradministration of assessments isalso poor, often not adhering tospecific departmental criteria.

Exam papers are generally poorlybalanced, with repetition and poormark allocation. They do not cover the correct material and questionsare not of the correct standard.Teachers are not capable ofmoderating each other’s papers.Heads of Department are not ableto judge the standard of others’papers, as they often do not knowthe syllabus.

Knowledge transferproblems

Other factors affecting knowledgetransfer include:

• Class discipline: is not aproblem, but many learnersare not punctual;

• Learners’ work discipline:Teachers feel they arepowerless with learners,therefore seldom disciplinethem or enforce work;

• Invigilation: There is littleteacher control during theexams.

• Organisation and Resources:General organisation andcontrol of textbooks andresources is exceptionally

poor (teachers andmanagement alike);

• Use of media: Many teachersdo not know how to utilisethe media resources, if theschools have them;

• Utilisation of laboratories:Very few educators conductexperiments during the term; they either cannot performthem, or a suitable laboratory is not available;

• Computer facilities: Some ofthe schools actually havecomputer rooms, but theyare generally unused.Support and operationalissues are often overlookedwhen donors open thesefacilities.

Teachers were asked to evaluatethemselves on six items, andthese were compared with thementors’ evaluations of them. Of a total of 174 items, teachersevaluated their abilities as higherthan the mentors’ evaluations on93 counts, and this self-rating was frequently two points (on a 5-point scale) higher than that of thementors. The indication here isthat the teachers have a poorframe of reference by which theyjudge themselves and their ownteaching practise.

Attitudes

• Teachers show no sense ofurgency dictating theirgeneral approach toteaching: they showedenormous time wastage interms of actual teaching time(teachers miss periods tosmoke, mark during periods,are slow in getting going, and

53

generally mismanage theperiod time; they take farmore leave than allowed andthere are no effectivecontrols);

• Teachers often do notindicate a passion or concernfor the learners, or a feelingof responsibility for thelearners’ success or failure,but are functional in theirtasks;

• Teachers generally have apoor work ethic during theterm (they do not have thewill or inclination to workhard); yet they may go toschool in theholidays togive classes inan attempt tocomplete thesyllabus. Theyshow littlewillingness toundertakeextra-muralactivities tobroaden thelearners’experience,e.g. participate in expos,science fairsand competitions.

• Teachers have a desire formaterial or information, butdo not bother to seek it out.

• Many teachers hide behindother issues to explain poorresults, e.g. timetableproblems and lack ofresources.

Department heads

The heads of department of maths and science are frequently biology

teachers, who struggle to givedidactic support to the teachers,and are often not particularlyinterested in the maths andscience departments. Theyfrequently feel that they do nothave authority over staff, and feelpowerless; therefore they do notmonitor or control teachers andtheir progress.

Very few subject meetings wereheld, and there was littlecollaboration between teachers.There is often only one teacherper grade level, which allows thatteacher to lag behind and not

complete thesyllabus as there isno monitoring orobservation takingplace.

Learners andschoolexperience

• Higher Gradeand StandardGrade issues: Alllearners aretaught on theStandard Grade

(SG) throughout school.Recently the TMP schoolshave started (misguidedly)allowing some learners tostudy maths and/or scienceon the Higher Grade (HG) ingrade 12 (approximately 10to 15% of matriculants),even though the subject hasonly been taught on the SGin previous years. However,the few HG students are nottaught HG work in class (dueto the fact that there may be

54

Heads of

department ....

feel they do

not have

authority over

staff, and that

they are

powerless to

control teachers

3 HG learners in a class of 40 SG). Instead, they receivetuition in the afternoons once a week, or self-study.

• Homework: Learners receivevery little homework andtherefore get littleopportunity to reinforce workdone in class. Even so,learners make little attemptto do their homework;

• Exams: Learners are notgiven their exam timetablesin good time for planning, sothey are unable to set up astudy programme/timetable;matrics stay at home afterprelims, and few return forrevision;

• School situation: Class sizesrange from 40 to 70 perclass, often exceeding theclassroom capacity; there are no functional libraries, andlaboratories are inadequateor not used for science.

Resources and discipline

Textbooks, desperately needed byteachers, are generally in veryshort supply, and often notbrought to school by learners.Most learners do not havecalculators and mathematicsconstruction sets, making it verydifficult to teach the syllabussections requiring these.

Science and maths learners inparticular do not see the relevance of science and maths in their lives, and are therefore unmotivated.

Many learners do not go to class,or are late for class; most do notdo their homework, and teachersfeel powerless to deal with anyindiscipline.

Learners in general are notprepared in any way for schooland what it means, and suchnegative issues with the learnersalso contribute to the lack of

55

Figure 3. Impact of English proficiency on learner performance in maths(Lawless, 2005)

enthusiasm and commitment onthe part of the teachers.

Language Issues

A dominant problem at the schools is the issue of language (Howie,2002). Lawless (2005) alsosurveyed this issue on a nationalscale and showed very clearly that there is a definite relation between English proficiency, as measuredin grade 12 symbols, and mathssymbols. This is shown in Figure 3where learner matric performanceis expressed in terms of theirmatric symbol in English as firstlanguage as well as secondlanguage. It was found thatnone of theteachers nor anyor the learners atthe TMP schoolshad English astheir firstlanguage, and yet the language ofinstruction andassessment isEnglish. In fact,in many cases the teachers’English is so poor that they teachin the vernacular, furtherdecreasing the learners’ chance ofmastering the language. Thewritten tasks set by the teachersare, in addition, frequently sopoorly set out and explained thatthe learners do not understandwhat is required of them.

Informal research was undertakento assess the extent of thelanguage problem, using samplegroups of learners. Their Englishproficiency levels were tested, asthis language proficiency will

obviously have an impact on theirmaths and science performance,since they are required to write allassessments in English.

As a benchmark or reference forthe English proficiency test resultsat the TMP schools, their resultswere compared with those ofsimilar sample groups of learnersat two other Tshwane schools(both government co-educationalschools):

• An English-medium schoolwhere most of the learnersspeak English as their homelanguage, and write exams in

English (B1 in the tablebelow);

• A school where most of thelearners speak English astheir second language butwrite exams in their homelanguage (B2 in the tablebelow).

TMP schools are discussed as agroup as they show consistentresults. In all of these schools thelearners speak English as asecond, third or fourth language,but they must do all their learningand assessment in English.

56

GradeBenchmark schools TMP schools

B1 (English) B2 (Motherlanguage)

Grade averages

8 39 38.5 21.5

9 48 37 22

10 62 43 24

11 58 46 24

Table 2: English Proficiency test results (all marks arepercentages)

The following observations may be made:

• Based on the norms expected per grade, no learner in thetest samples at any of theTMP schools has an Englishlanguage proficiency evenequal to that of a grade 7learner;

• While the benchmark schoolsshow a trend indicating anincrease in marks as thelearner progresses throughthe school to higher grades,this is not seen at the TMPschools, despite the fact thatall learners attend Englishlessons daily.

Learners’achievements inmaths and scienceassessment willcertainly benegatively affectedas theirunderstanding oftheir questions willbe very poor, andthey will not be able to express theiranswers in English.Although the impact on their maths andscience assessment marks cannotbe quantified, it could be assumed that these marks would, as aconsequence, be at least a symbol lower than the mark that would be a realistic evaluation of theiractual maths and scienceknowledge.

School managementissues

The following observations weremade regarding the school

management as it impacts on themaths and science outreachefficiency of TMP. It isacknowledged that it may betainted with subjective opinion,but other audits confirm theseobservations (Fricke et al, 2006)

• Principals do not use theirauthority to insist on certainteaching practices, do notmonitor individuals ordepartments, and do nothave overall school control;

• Lack of system andorganisation at every levelaffects teaching across theboard, e.g. compilingtimetables, poor timing ofperiods and inadequate

teachermanagement;

• Climate oflearning: Theschoolatmosphere isnot a formallearning one.There are regular social days(spring day,beauty pageants) in which teachers do not teach somany learners do

not attend school;• Shortage of funds: As a result

of funding shortages learnersdo not receive nearlysufficient photocopiedmaterial, there is sometimesno electricity, and learnerscannot be sent on excursions. This is partly due to parents’non-payment of school fees.

• Inadequate vocationalguidance: teachers areunable to motivate andinform the learners. Most of

57

Learners do

not see

opportunity for

themselves

to work in

the fields of

mathematics

and science

these township schools donot receive the attention ofrepresentatives from thetertiary institutions becausethe latter prioritise thoseschools which are moresuccessful; as a resultlearners most in need ofmotivation do not receivesuch incentives.

STEM exposure

(a) Learners: Learners in general have no goals for the future, andparticularly do not see opportunity for themselves to work in thefields of maths and science. Theyhave received little exposure toScience,Technology,Engineering andMathematics (STEM) and are unaware ofcareers that mightbe open to them inthese fields. Theyalso tend to think of these vocations asunattainable forblack children ofpoor financialmeans.

(b) Teachers: Teachers do notknow what is involved in thevarious careers, and thereforecannot advise their learners. Withthe change in curriculum (FET in2006) teachers do not know howto advise learners in terms ofsubject choice e.g. whether tostudy maths or maths literacy.

Conclusion

There are therefore several factors that must be addressed

simultaneously while mentoringthe teachers in an educationsupport programme at schools.

It is of little worth to improve ateacher’s skills if that teacherfaces learners who are negative,bored or unmotivated, and do notsee the value of the subject thatthe teacher is trying to teach.Thus it is important to cover allteacher aspects, as well as tryingto assist with improving generalschool problems, and supportingthe learners academically and interms of their motivation.

Social engineering projects, suchas JIPSA, also function within a

system. Thereforeone cannot onlyconcentrate on theoutput side andignore the largerproblem on theinput side. It seems that the currentJIPSAimplementation issuffering from anaïve short termvision and lack ofappreciation of

system functionality.

There seem to be clear indicationsthat short term targets tend to beset in isolation, with political intent, ignoring the realities of the biggerpicture. The result is that the JITprinciple is applied withoutunderstanding that scarce technical skills depend on the availability ofvery basic maths and science skillsat school level. This paper hasshown that the education system is terminally flawed and in need of asystemic overhaul. A well

58

It is unproductive

to concentrate

on the output side

while ignoring

the larger

problem on the

input side

documented successful maths andscience outreach programme used to unpack the underlying systemicproblems clearly shows that noamount of tinkering with theexisting system will ever producethe desired results, and notreatment of symptoms will help.What is needed is an appreciationof the underlying problems in thetotal education system which willtake more than politicallyexpedient statements and decreesto be effective. The final conclusion therefore is that the JIPSA initiative is therefore not just in time, butjust out of time! q

References

I. Fricke, E. Horak, L. Meyer and N. van Lingen (2006): Lessons from amathematics and science interventionprogramme in Tshwane township schools. Centre for Research on EngineeringEducation (CREE) Conference. September2006, University of Pretoria, Pretoria,South Africa.

I. Fricke, E. Horak (2006): Observationsfrom an intervention programme insecondary township schools in the Tshwane area to address the maths and sciencecrisis. Paper submitted for publication tothe South African Journal of HigherEducation (SAJHE). Pretoria, South Africa.

E. Horak (2003): Developing the smallschool pool for engineering in South Africa. Proceedings of the 7th Baltic RegionSeminar on Engineering Education, UICEEseries with UNESCO support, StPetersburg, Russia, September 2003.

I. Fricke, E. Horak (2004): BuildingCapacity by mentoring Mathematics andScience Teachers. Paper accepted andpresented at the 7th Conference on AsphaltPavements for Southern Africa, 2004, SunCity, South Africa.

S. Howie (1999): Report on Science andTechnology Centres in South Africa. Human Sciences Research Council. Pretoria 1999.

S. Howie (2002): English proficiency andcontextual factors influencing mathematicsachievement of secondary school pupils inSouth Africa. PhD Thesis, University ofTwente, Netherland, 2002.

A. Lawless (2005): Numbers & Needs:Addressing imbalances in the civilengineering profession. South AfricanInstitution of Civil Engineering, September 2005.

H. Le Roux (2006): Brain gain.Engineering News, 15-21 September 2006.

M. Mangena (2004): Speech presented at CSIR Conference Centre. Minister ofScience and Technology, CSIR ConferenceCentre, April 2004.

National Strategy for Mathematics,Science and Technology Education(2004): Creating Tomorrow’s Stars Today.Implementation Plan 2005 – 2009,Department of Education Document, 2004

M. Porter (1990): The competitiveadvantage of nations. Macmillan Press,1990, New York, United States Of America.Sunday Times Newspaper, 2 January 2005.

N. Taylor, J. Muller and P. Vinjevold(2003): Getting Schools Working.Research and Systemic School Reform inSouth Africa. Pearson Education, SouthAfrica.

HSRC Media release, Internet,www.hsrc.ac.za/media/2004/12/20041214

59

From 1997 to 1998 Sabitaran an extremelysuccessful empowerment

programme for municipalitiesknown as the Local CouncillorEmpowerment Programme(LCEP). The objective of thisinitiative was to expose newlyelected councillors to theimportance of roadsfor improvingservice delivery, and their role in themanagement andimplementa- tion ofroad provision.

Over a two-year period close to 100workshops wereconducted in theKwaZulu-Natal,Western Cape andGauteng provinces,with just over 1000councillors and officials participating.

These workshops,conducted shortly after the elections of 1994,

provided the first opportunity formany of the local councillors to beinvolved in the decision makingprocess associated with theallocation of budgets and themanagement of infrastructurewithin a local authority. Much ofthe success of the workshops wasthe result of the skilled facilitation

provided by Sabitamembers, and theemphasis on theimportance of roads inservice delivery.Members in turn werealso sensitised to theneeds of thecommunities in whichthey operated, enabling them to optimise theirspectrum of servicesand productsaccordingly.

Public awareness campaign

In 2002 the format forthe LCEP was changedfrom that of facilitationbased workshops to a

61

Sabita's Local Councillor Programme:

Improving service deliverythrough appropriate roadmaintenance

Mike Winfield

DirectorZebra Bituminous Surfacings cc

Sabita’s LCEP booklet on the need to maintain roads

public awareness programme toillustrate the benefits of goodroads to the social and economicdevelopment of previouslydisadvantaged communities. Theprogramme included bus tours tothe townships of Soweto inJohannesburg and Khayelitsha inCape Town for councillors, officials and media personnel, who wereable to view at first hand theeffects of roads on the social andeconomic development of thoseareas.

These tours clearly illustrated toall participants thebenefits that accrue to the communityfrom a good roadinfrastructure incomparison to areas where there was alack of good roads. In a report backsession, 85% ofcouncillorsrecognised the need for roadmaintenanceexpenditure toreceive a higherpriority than directsocial spending e.g. housing andschools. With the newunderstanding that roads shouldbe seen as the “arteries of anation”, the councillors rated 42%of our roads as being “in a poorcondition”. It became clear thatthe fundamental message of howa well maintained roadinfrastructure impacts positivelyon our society was clearly gainingacceptance.

Improved in servicedelivery

South Africa has recently enteredthe third election period for localcouncillors since thedemocratisation of South Africa.While the role of the councillorshas not changed, Sabitarecognised that there was apressing need to improve thecommunication process betweencouncillors and appointed officialsif the backlog in maintaining ourageing road infrastructure was tobe adequately tackled. This

understanding hasbeen highlighted bythe reduction infocus and spendingon routine roadmaintenance inmany localauthorities.

With this in mindSabita proposes torun a revised seriesof seminars underthe banner,“Improving servicedelivery throughappropriate roadmaintenance”. It is

intended that a broader crosssection of appointed officials andelected councillors will berepresented at these seminars,including staff from the financialand the technical departments.

It is important therefore that these seminars should not be highlytechnical, but should focus on theimportance of asset preservation.This approach augments andsupports government’s growth

62

85% of councillors

recognised

the need for

road maintenance

expenditure

to receive a

higher priority

than direct

social

spending

strategies as promulgated by theASGISA objectives.

The proposed seminar will focuson three main areas:

• The requirements of theMunicipal FinanceManagement Act (MFMA),which requires that localauthorities report annually on their fixed assets includingroads. These reports arerequired to indicate the levelof depreciation orappreciation of these assets;

• The second focus area is tohighlight the actual status ofthe road network in theregion where the workshop is being conducted;

• The third focus area will givea brief overview of bestpractice and solutions toensure a well-maintainedmunicipal road network.

The seminars will conclude with apanel discussion in whichdelegates may express their views and chart a way forward.

The first seminar is scheduled tobe held in the Western Cape on 15 March 2007. Based on theexperience gained at this seminar, further seminars will be hosted inother regions. Sabita hascommissioned a public relationscompany to assist with themarketing of these seminars tomaximise the attendance of thelocal councillors and to ensure that they are not intimidated by thetechnical aspects of the seminars.

SALGA Endorsement

Sabita is also seeking theendorsement of the seminars bySouth African Local GovernmentAssociation (SALGA) to help inmotivating the hosting of seminars in other provinces.

To build on one of the key success factors in the implementation ofthe previous LCEP, the intention is to optimise the involvement ofSabita members. Sabita membersoperating in an area whereseminars are to be conducted willbe invited to set up smallexhibition stands or display theirequipment. This strategy willprovide Sabita members with anopportunity to display theirparticular areas of service in theurban road maintenance arena,and to interact with municipalofficials and councillors in anenvironment of learning andempowerment.

To reduce the time in preparingfor the successive seminars, it isintended that the contents of each presentation be packaged in a way that ensures ease ofcommunication. Sabita hasprepared an informativenon-technical hand out on theimportance of maintaining asurfaced road network that maybe used as reference material bythe delegates.

Any organisation or personwishing to conduct a seminar intheir region should telephoneTrevor Distin at 021-531 2718, ormake contact by email throughinfo@sabita.co.za. q

63

While the asphaltindustry benefittedfrom the strong

growth in the constructioneconomy in 2006, SAT’sleadership is committed toensuring that the same growth impacts positively on theSociety in new and innovativeways. But firstly let us reflect a while on the past year, duringwhich some really good thingshappened.

As a Society for individuals, it isincumbent on all regional officersto ensure that there is adequatedelivery to members in theirareas. This has not really been toour satisfaction in the past, andthere is now strong motivation and intent to turn this around.

I am pleased to report that theregions, under the chairmanship of Basil Jonsson (Central), CraigBradley (Eastern) and GraemeMcGregor (Southern), experienced a surge in activity during 2006,and their good work deserves theproper recognition.

Some examples are:

• The Eastern, Southern andCentral regions all convenedwell attended workshops onthe latest European trends inwarm asphalt technology;

• All regions took part in theSabita road show arranged to highlight industry efforts tophase out the use of coal tarproducts;

64

Surge in SAT's knowledge transfer activities:

2006 activities generate a newvision of member service

John Onraët

PresidentSociety for Asphalt Technology

Basil Jonsson,Chairman, Central

Region

Craig Bradley,Chairman, Eastern

Region

Graeme McGregor,Chairman, Southern

Region

• The Eastern Region held ahighly successful seminar onthe interpretation of asphalttest results, as well as theuse of the Bailey Method as a means of determiningbehavioral aspects ofaggregate as part of an HMAdesign. Another seminar washeld in this region to discussthe pros and cons of asphaltreinforcement;

• The Southern and Easternregions heldtechnologyexchangefeed-backsessions where variousdelegates tothe ICAPconference inCanada shared their newknowledge and experiences;

• The Southernand Centralregions heldsuccessful,well attendedworkshops onthe current status of UltraThin Friction Courses.

Although individuals from theclient body sector (both membersand non-members) do oftenattend SAT functions, we wouldlike to see attendance numbersincrease in future. SAT providesexcellent networking opportunities and is an ideal discussion forumfor all individual role players in the industry. The council willproactively be encouraging localauthorities to support their staff in attending future meetings.

It is pleasing to note the improved attendance at seminars in theCentral Region, which recordedthe highest number of delegates.

While the asphalt industry in KZNis simmering down somewhatcompared with the rest of thecountry, it is encouraging to notethe ever-increasing number ofemerging consultants andcontractors who are attending SAT seminars. This will now become a

key focus area ofSAT and allpractitionersinvolved with theemerging contractor and consultantmarket are urged to encourage them toattend seminarsand eventually joinas members of theSociety.

Most importantly, Ican proudlyannounce that SATis now financiallysecure and healthy,and our financial

woes are thankfully a thing of thepast, due mainly to concertedefforts by the Council (moreespecially the regionalchairpersons).

However, this does not entitle usto relax or to rest on our laurels.We now have the opportunity togrow the Society and improve onour current success.

Our aim is to develop and enhance our status as a Learned Societyand to position SAT locally andinternationally as a reputable

65

Our aim is to

develop and

enhance our status

as a Learned

Society and to

position SAT

locally and

internationally

as a reputable

organisation

organisation. With theimprovement in our financialsituation, the Council is now in astronger position than ever todeliver improved services to ourmembers. Priority will be given to thefollowing issues in the year tocome, although the list is notexhaustive:

• There will be further rational- isation and streamlining ofour accounting andadministration functions;

• There will be a concerteddrive to enhance the deliveryof technology exchangeamongst our members, withimproved quality of seminarsand workshops, and moreconnectivity with overseasspecialists;

• In the process of streamlining of our administration, amembers’ newsletter will beproduced;

• SAT will have an opportunityto heighten our profile atboth CAPSA 2007 and at theRoad Pavements Forum;

• Closer ties and cooperationwith other important industry

bodies, such as Sabita, AsAc,ASPASA, SAFCEC, IMESA, isseen as a priority;

• There will be continuousimprovement of our website,and members will have theopportunity to coerce theiremployers to advertise orsponsor pages;

• We will keep membersabreast of industryoccurrences overseas,reporting back as they occur;

• We will maintain a positivestate of our financial healthto create and deliver valueto our members;

• The allocation of CPD pointsis under investigation and will be available to members;

• Regional chairpersons will beencouraged to find newmembers.

In closing I would like to thank allCouncil members who have put in“sweat equity” into ensuring thecontinuation of the Society. I know it is all voluntary and may thispositive spirit continue. q

66

After six years ofoperations during whichmore than 3 750

delegates attended 98educational events organisedby AsAc, the academy is nowpoised to make a majorcontribution to continuingprofessional development(CPD) and personal growththrough the presentation of acomprehensive course onFlexible Pavement Engineering

The first course is scheduled forpresentation from March 2007 toMay 2008 in Pretoria, inassociation with the ContinuedEducation Section of the University of Pretoria.

The development of this course isan exciting new initiativeinstigated during the 2005/06 inresponse to an industry needssurvey undertaken by the CSIR on behalf of the Asphalt Academy.The survey reported that roadauthorities, consulting engineersand other practitioners had raisedconcerns about the lack of

pavement engineering knowledgedisplayed by recently graduatedcivil engineers, technicians andtechnologists. In the past, thisshortcoming has forced employers to deploy significant resourcesover several years to ensure thatyoung engineers had thenecessary know-how to carry outtheir duties effectively.

There were several motivatingfactors for the development andpresentation of such a course.Although various institutions offersimilar courses either on demandor as part of a continuingeducation programme, most ofthese are infrequently available,and often have insufficientpractical content.

Various tertiary institutions offersemester block courses onTransportation Engineering orUrban Engineering either as a part of a postgraduate qualification, orsimply for individuals to gainfurther information. However,actual lecture time is relativelylimited, requiring that a largeamount of the learning be

67

AsAc activities focus on CPD:

Flexible pavement engineeringcourse to cater for industryneeds

Les Sampson

CEOThe Asphalt Academy Trust

accomplished through self-study.The consequence is that severalyears pass before a newlygraduated engineer has sufficientknowledge to fully contribute tohis/her firm’s workload.

In response to the industry needs, the extensive and flexiblecurriculum is structured into seven modules involving 11 weeks ofclassroom study over a 14 monthperiod, supplemented by projectwork in the learner’s home office.

Participants whosuccessfullycomplete the course will gain creditstowards apostgraduatequalification whererequired. Creditstowardsprofessionalregistration are also being discussedwith the relevantauthorities.

An integral part of the coursestructure is to guide the learnerthrough the inception, design andconstruction of both a new roadand a rehabilitation project. Theproject assignments will beconsistent to all the modules, withwritten and oral submissions toencourage the students to applythe theoretical knowledge gainedthrough lectures to actualprojects. At the end of the course,students will be required to submit a final oral project reportsupplemented by an extensiveproject file for assessment.

Other ad hoc initiativesundertaken during recent years inresponse to industry needs havebeen the presentation of theQuality Management of Bitumencourse in 2005, which willhopefully be repeated on requestduring 2007/08, and AchievingVolumetrics and Compactabilityusing the Bailey Method duringNovember 2006. An internationallecture and workshop onAcceptance Control and QualityAssurance of HMA is also

scheduled forFebruary 2007.

In addition, thefollowing regularcourses will still beoffered on aregional basis:

• Introduction tobituminousproducts;

• Application andconstruction ofsurfacing seals;

• Design of surfacing seals;• Manufacture, application and

construction of hot mixasphalt;

• Design of hot mix asphalt(including the application ofthe Bailey Method;

• Compaction of hot mixasphalt (in conjunction withSARF).

To ensure that best practicemanuals currently published byAsAc are relevant to currenttechnology, TG1 – The Use ofModified Bituminous Binders inRoad Construction is beingupgraded and revised by anindustry task group for distribution

68

Participants who

successfully

complete the

course will

gain credits

towards a

postgraduate

qualification

in the first half of 2007. TG2 – The Design and Use of FoamedBitumen Treated Materials will bereplaced in 2008 by a BitumenStabilisation manual incorporatingfoamed bitumen and emulsiontreatment of materials. Thisdocument will be finalised oncompletion of the researchcurrently being sponsored bySabita and the Gauteng

Department of Public Transport,Roads and Works.

The full AsAc course schedule for2007/08, including detailedinformation on the courses, dates,regional location and costs, isavailable on the AsAc website athttp://asphaltacademy.co.za. Thewebsite also offers an on-lineregistration facility. q

69

4

Innovation

Far from being a wasteproduct of the steelproduction process, steel

slag is a high quality resourcefor use as an aggregate in road construction, and as such itshould be seriously considered as a viable alternativeaggregate in hot mix asphalt.

Due to the changes in trafficloading spectra and higher roadsurface temperatures beingexperienced in South Africa,numerous investigations havebeen undertaken to assess theproperties of asphalt mixes toimprove durability, and resistanceto fatigue fracture anddeformation. One suchinvestigation examines the use ofsteel slag as an aggregate inasphalt mixtures.

As a result of increasing focus onthe environmental requirementsfor the acceptable disposal ofwaste slag, as well theconsiderable strain on the alreadylimited number of aggregateresources, steel slag is beingincreasingly considered as an

alternative to natural aggregatesin the road construction industry.

Slag production

Steel slag is produced during theseparation of molten steel fromimpurities in steel-makingfurnaces, and is composed ofcalcium silicates together withoxides and compounds of iron,manganese, alumina and othertrace elements.

Free lime and magnesium oxidesthat have not reacted with thesilicate structures can hydrate and expand in humid environments,which is precisely what happenswith steel. Consequently, slagaggregates exhibit a tendency toexpand. Volume changes of up to10% or more, attributable to thehydration of calcium andmagnesium oxides, can causedifficulties.

For this reason it is important thatfurther weathering of the steelslag takes place to cause the freecalcium oxide to hydrate. If the

73

A viable alternative to natural aggregates:

The use of steel slag aggregatein asphalt mixes

Hugh Thompson

DirectorWSP SA Civil andStructural Engineers(Pty) Ltd

Michael Bouwmeester

AssociateWSP SA Civil and Structural

Engineers (Pty) Ltd

calcium oxide is not fully hydrated, the presence of water can causehydration and the further breaking down of the aggregate. In a steelslag asphalt mix this is character-ised by isolated white deposits ofcalcium carbonate, which isformed by the hydration andcarbonation of free lime close to or at the surface of the aggregate.

Consequently steel slag destinedfor use as an asphalt aggregateshould be stockpiled outdoors forup to 18 months to expose thematerial to moisture, either fromnatural precipitation or thedeliberate application of water, toensure that potentially destructivehydration and its associatedexpansion takes place prior to itsuse as an aggregate in asphalt.

The properties that have to beevaluated for the suitability of slag as an aggregate relate to thechemical, physical and mechanical

nature of the material. Table 1gives indications of the typicalproperties of steel slag, doleriteand quartzite.

Physical properties

The unique properties of steel slag improve the performancecharacteristics of asphalt materials in a number of ways. These arediscussed below.

Density: Particle density of thesteel slag aggregate compared tothe dolerite and quartziteaggregates in Table 1 indicate that steel slag is a more dense and,hence, heavier material. Thedisadvantageous financial effect of this higher tonnage demand has to be offset by the price of steel slagaggregate compared toconventional aggregates to rendermixes using steel slageconomically viable.

74

Property Steel slag 13.2mm

Steel slag 9.5mm

Steel slag -3.0mm

Dolerite13.2mm

Quartzite

Free lime (%) 2.36 2.36 2.36 N/A N/A

pH 12.8 13.1 13.1 8 5

Particle density(kg/l) 3.239 3.188 3.319 3.069 2.7

Water absorption 1.1 2.1 2.4 0.7 0.3

Flakiness index 3.9 7.7 - 20 23

Ten Percent FinesValueWetDry

460490

460490

- 315350

236299

Aggregatecrushing value

WetDry

7.3-

7.3-

--

1311

2015

Polished stonevalue

63 63 63 52 55

Table 1: Steel Slag, Dolerite and Quartzite Properties

Water absorption: Steel slag istypically more absorbent thandolerite and quartzite, a propertyarising from the nature of the steel slag aggregate and the manner inwhich it is produced. This has theeffect of higher binder absorptionthan would be expected of dolerite or quartzite. This is an importantfactor that needs to be consideredin the evaluation of the mixdesign, especially whendetermining volumetric properties.

Flakiness index:The flakiness indexof the steel slagaggregate ismarkedly lowerthan that of dolerite and quartziteaggregates. Themore cubical shapeof the slag enablesthe formation ofstrong interlockingstructures withinthe asphalt mixture, which exhibits highstiffness andexcellent resistanceto permanentdeformation.

Aggregate strength: The highTen Percent Fines and the lowAggregate Crushing Valueindicates the high density andcrushing strength of the steel slagaggregate, properties whichensure substantial resistance todegradation under traffic loading. pH value: Steel slag, with a pH of between 8 and 11, has a strongaffinity for bitumen and, therefore, displays a greater degree of binder retention. This is a very important

characteristic in relation toresistance to stripping and,consequently, long-termdurability, and it makes steel slagan ideal aggregate for enhancingthe life of asphalt mixtures.

Polished stone value: A polished stone value of 63 for steel slagaggregate indicates a highresistance to the polishing of theaggregate surfaces under theaction of traffic, which augurs wellfor providing a texture that

promotes skidresistance. It isusual for anaggregate having aPSV in this range to have a poorabrasion value, asthe resistance topolishing can beattributable to lossof particles orgrains from thesurface of thestone. Steel slag,however, also hasexcellent resistanceto abrasion. This isan unusual

combination of properties, makingsteel slag a safe and durablealternative to natural aggregates.

Free Lime: The application ofsteel slag aggregates in roadconstruction is only practical ifthere is sufficient volumetricstability – a property indicated bythe presence of free lime. Asindicated in Table 1, the free limecontent of the steel slag aggregate tested is 2,36%. A maximum limitof 5% free lime is used as acriterion to evaluate whether anaggregate is suitable for use in

75

The more

cubical shape

of the slag

enables the

formation

of strong

interlocking

structures

within the

asphalt

road construction. As mentionedpreviously, the weathering of theaggregate is of utmost importance to the stability of the aggregate,and is considered to be one of themost important aspects of rawmaterials handling.

Steel slag asphalt mixes

The objective of investigating steel slag asphalt mixtures was toproduce a rut resistant asphalt forapplication where traffic loading ishigh, vehicle speeds low, andenvironmental conditions varying.Trial steel slag asphalt mixes were prepared for use during the N3Toll Concession (N3TC) routinemaintenance contract betweenHeidelberg and Cedara.

A mix design was completed using the steel slag as an aggregate,along with a filler to satisfy the-0,075mm grading limits. Thegrading specification used for themix design was according to TRH8(Coarse). A 4% SBS modifiedbinder was used to enhance thenatural properties of the bitumenby making the binder more elasticat higher temperatures, which inturn enables the binder towithstand repeated traffic loadingand reduces rutting potential.

Results

For the mix adopted, thespecification required a stabilitywithin the range 8,0 kN – 18,0 kN. Test results indicated a stability inthe region of 15,0 kN. This can inpart be attributed to both the useof steel slag as an aggregate, andto the polymer modified binder.

The higher stability indicated thatthe mix was ideally suited to therequirements of a deformationresistant asphalt surfacing. Themaximum flow recorded at thevarious binder contents tested was 4mm compared to the recommen- ded range of 2 – 6mm.

The Indirect Tensile Strength (ITS) of the mix is a measure of thestiffness of an asphalt mix i.e. how well it distributes loading tounderlying layers. In the Interimguidelines for the design of hotmix asphalt in South Africa 2001,the minimum recommendedstiffness for a surfacing mix is1000 kPa. The stiffness of thesteel slag mix design reported,1280 kPa, is significantly higherthan this minimum requirement.

The above document alsorecommends a minimum Voids inMineral Aggregate (VMA) of15,0%. Low VMA asphalt mixestend to be sensitive to changes inbinder content and create tendermixes that may be more inclinedto rutting and bleeding. Theminimum VMA recorded for thebinder contents tested – 16,3% –exceeds the minimum requirement and is suited to a rut resistant and durable asphalt surfacing.

To optimise void content tocounter air and water permeability on the one hand, and fattiness and bleeding on the other, a targetVoids in Mix (VIM) of 4% wasadopted, as suggested bySuperpave 2001. The reportedresults for the steel slag mixdesign, was very close to theoptimum voids content of 4%, and the mix met the requirement for

76

air permeability recommended inTRH8 (1987) which is less than1,0 x 106 cm3/second.

The required Voids Filled withBinder (VFB) should lie between65% and 75% (Superpave 2001).The values of VFB obtained in themix design are slightly on the high side, due to the high VMA, which,along with the voids in the mix,determine the VFB.

Additional testing

Gyratory Testing: This test gives an indication of the compactabilityof a mix, and reasonably simulates in-service compaction undertraffic. From Table 2 it can be seen that the steel slag mix at variousbinder contents satisfies thegyratory testing requirementsgiven in the Interim guidelines forthe design of hot mix asphalt inSouth Africa 2001.

The results indicate that the mix is not easily compacted under traffic, and is therefore considered to be a rut resistant mix which willperform well in service.

Wheel Tracking Test: Cores of150mm diameter were removedfrom four locations forcomparative testing using theModel Mobile Load Simulator

(MMLS) apparatus. The resultsobtained can be seen in Table 3.

These test results indicate that the steel slag asphalt displayssomewhat better resistance todeformation than the Doleriteasphalt and SMA samplesevaluated.

Volume Expansion: Asmentioned before, it is of utmostimportance that the steel slagaggregate used for road construc-tion is volumetrically stable. Toevaluate the stability of steel slagaggregate once it has beensubjected to weathering, volumeexpansion testing is undertaken as a quality control measure. Typical- ly, the volume increase of thesteel slag aggregate is dependenton time, and this behaviour, for all steel slag, is usually asymptotic,with a high rate of initial volumeexpansion decreasing with time tovirtually zero.

Soluble Deleterious MaterialTest: Steel slag is further required to be tested for soluble deleterious materials.The required minimumaccording to SABS 1083 is 85%, and therefore the sample isconsidered to be acceptable.

Grip Tester FrictionMeasurements: Grip Testerfriction measurements were

77

Design Specification

Percentagebinder

4.7% 4.8% 4.9% 5.0% 5.1% Voids E80s

Voids @ 125gyrations

5.1 4.9 4.8 4.3 5.4 Min 4.0 >10x106

Voids @ 300gyrations

3.9 2.6 2.6 2.7 3.3 Min 2.5 >10x106

Table 2: Gyratory Test Results

78

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undertaken on a trial sectionconsisting of a 13,2mm singleseal, with steel slag as anaggregate on the south boundlane and shoulder, and dolerite asan aggregate on the north boundlane and shoulder. The results arepresented in Table 4.

The results indicate that the steelslag aggregate provides a moreskid resistant surface than thecorresponding dolerite aggregate.

Performance

As can be seen from the abovetesting, the steel slag asphalt mixcomplies with normal designcriteria and indicates that thisaggregate can be effectively usedto improve the properties of anasphalt mix.

Because site conditions may notalways be emulated by laboratorytesting, in-service assessment was carried out, and this has indicatedthat, to date, the performance ofthe mix on the road has beensatisfactory, with no problemareas evident.

Environmentalconsiderations

Today we have an obligation toconsider the impact of our actionson the environment, especiallywith regard to preservation andsustainability. By using steel slagas an aggregate, the environmentis reaping a two-fold benefit. Themost obvious environmentaladvantage is the preservation ofprecious natural resources, and

another benefit is a reduced needto dispose of the material inlandfill sites.

There is however one negativeperception associated with the use of steel slag aggregates, and thisis the leaching of chemicals fromthe slag aggregate into thegroundwater and resultantnegative impacts on theenvironment. However, studiesundertaken in Germany haveshown that this leaching ofchemical elements is insignificantin terms of environmental impact,and should not be considered anissue of concern in terms ofenvironmental health andsustainability.

79

Carriageway Steel slag (southbound) Dolerite (northbound)

Lane/position Shoulder Outerwheelpath

Innerwheelpath

Shoulder Outerwheelpath

Innerwheelpath

Ave. grip no. 0.62 0.62 0.71 0.56 0.59 0.59

Std. dev. 0.0381 0.0355 0.0336 0.0171 0.0157 0.0164

Minimum 0.50 0.51 0.56 0.52 0.50 0.53

Maximum 0.77 0.75 0.79 0.62 0.62 0.62

90th percentile 0.58 0.59 0.68 0.55 0.57 0.56

Table 4: Grip Tester Friction Measurements

Conclusions

From the results presented, it canbe seen that steel slag produces ahigh quality aggregate, which canyield a number of benefits interms of improved skid resistance, resistance to permanentdeformation and durability. Roadowners, road users and theenvironment benefit from the useof steel slag as an aggregate inthe road construction industry.Steel slag aggregate is indeed avaluable commodity to the roadconstruction industry, and shouldbe considered as a viablealternative aggregate in the roadconstruction industry. q

References

1. Asphalt Institute: Mix design methodsfor asphalt concrete and other hot mixtypes. MS-2. Sixth edition.2. Asphalt Institute: Superpave mix design, Superpave series No. 2 (SP-2). Thirdedition 2001. United States of America.3. Colarado Department of Transportation:Contract No. CMS 804-99. January 2001:Development of a new high performanceasphalt mix for 1-70 through GreenwoodCanyon. CTL/Thompson Inc. Colarado.4. Committee of State Road Authorities.TRH8:1987. Selection and design of hotmix asphalt surfacings for highways. SouthAfrica.5. European conference on slags. Marseilles 25-27 March 1988. Proceedings: The steelslags, characteristics and properties. DrIng. H Motz.

6. Euroslag: Engineering of Slags, AScientific and Technological Challenge. 2ndEuropean Slag Conference. 9-11 October2001 Dusseldorf. Proceedings: Progress inthe utilisation of steel slags in the UK.G.H.Thomas: Thomas Research ServicesLtd. United Kingdom.7. Euroslag: Engineering of Slags, AScientific and Technological Challenge. 2ndEuropean Slag Conference. 9-11 October2001 Dusseldorf. Proceedings: EAF Slag inAspahlt. N.Jones – Steelphalt. UnitedKingdom.8. Hot mix asphalt design Project.September 2001. Interim guidelines for the design of hot mix asphalt in South Africa.9.http://www.tfhrc.gov/hnr20/recycle/waste/ssa3.htm10. http://www.tfhrc.gov/hnr20/recycle/waste/ssa1.htm11. Ohio Department of Transportation.November 1993. Report No.FHWA/OH-94/004. Precipitate potential ofhighway subbase aggregates. J.D.Guptaand W.A Kneller.12. Oregon Department of Transportation.State Research Project #511. April 2000.Steel slag in hot mix asphalt concrete. Final report. L. Hunt and G.E. Boyle.13. Steelmaking Slag Technical Committee. 1993. Steel Slag Aggregates Use in Hot Mix Asphalt Concrete. Final Report, preparedby John Emery Geotechnical EngineeringLimited. USA.14. Transportation Research Board.National Cooperative Highway ResearchProgramme, Synthesis of Highway Practice199. Recycling and use of waste materialsand by-products in highway construction.R.J. Collins and S.K. Ciesielski, WashingtonDC 1994.15. United States of America. NationalCooperative Highway Research ProgramSynthesis of Highway Practice 199,Transportation Research Board. 1994.Recycling and Use of Waste Materials andBy-Products in Highway Construction.Collins, R. J. and S. K. Ciesielski.Washington DC.

80

Over the past twodecades many SouthAfrican pavement

engineers have become awareof mounting pressure toconserve the environment,coupled with a decreasingavailability of crushed stonematerial.

These two issues have prompted a radicalre-assessmentof the mannerin whichpavementdesign is beingapproached inSouth Africa.

Traditionally,pavementdesignphilosophy inSouth Africawas based to alarge extent onthe assumptionof readilyavailable andcost effectivecrushed stone

(G1 material in particular, asshown in Figure 1). However, inthe face of decreasing availabilityof such material, engineers nowhave to improvise and recycleexisting pavement layers, asopposed to simply importing newcrushed stone material.The treatment of existingpavement layers with bituminousmaterials, either in the form of

82

Bitumen stabilised materials:

In search of sustainablepavement design solutions

Dr Fritz Jooste

DirectorModelling and Analysis

Systems (MAS)

Kim Jenkins

ProfessorSANRAL ChairUniversity of Stellenbosch

Figure 1: Breakdown of some structure types in the TRH4(1996) catalogue for design traffic greater than

3 msa, highlighting the strong reliance of current design guidelines on crushed stone

bitumen emulsion or foamedbitumen, offers a feasible and cost effective solution to the problem of providing sustainable pavementdesign solutions. However, thischallenge is not without obstacles, and most significant of these is the lack of sound and practicalguidelines to the design and use of bitumen stabilised materials.

Structured experience

Inadequate guidelines haveresulted mainly from the lack ofstructured and documentedexperience related to the design,use and performance of bitumenemulsion and foamed bitumenmaterials.

To address these issues, Sabita, in conjunction with the GautengDepartment of Public Transport,Roads and Works (GPTRW),initiated a project to developupdated guidelines on the designand use of Bituminous StabilisedMaterials (BSM).

This initiative aims to incorporateboth emulsion and foamedbitumen materials in a single BSMguideline to promote rationalmaterials selection and equitablecompetition between the twomaterial types. This guideline willupdate the technology presentedin current guidelines for thesematerials (e.g. TG2 – InterimTechnical Guidelines: The designand use of foamed bitumentreated materials, Sabita Manual14: GEMS – The design and use of granular emulsion mixes, andManual 21: ETB – The design anduse of emulsion treated bases.)

The Project

The project to develop a guidelinefor the design and use ofbituminous stabilised materialswas initiated in early 2005. At theoutset, it was recognised that thestructural design and mix designelements of the existing guidelines required the most urgent andsignificant improvements. Theproject was therefore structured to address these two aspects in acomprehensive manner. Owing tothe ambitious scope of the project, it was structured to allowexecution in distinct phases, asshown in Figure 2.

The mix design element of theproject is being undertaken byProfessor Kim Jenkins of theUniversity of Stellenbosch, whilethe Structural Design element isbeing handled by Drs. Fritz Joosteand Fenella Long of Modelling andAnalysis Systems (MAS).

As shown in Figure 2, the secondphase of the project is currently in progress, and the bulk of this work is scheduled for completion inearly 2008, at which time thecompilation of the guidelines willbegin.

Mix Design Developments

The mix design component of thisstudy aims to identify theinadequacies in currentapproaches to foamed bitumenand bitumen emulsion mix designprocedures, and to explorelaboratory test protocols andavailable laboratory test data forthese materials that would provide

83

a more fundamental, reliable mixdesign method for cold mixes ingeneral.

The overall framework of TG2 wasfound to be well-founded but notcomprehensive, and certaincomponents to the mix designprocedure were found to belacking. In addition, this projectaims to use more explicit mixdesign tests to classify theemulsion and foamed bitumenmixes for pavement design

purposes. The mix designcomponent of the study thereforehas four main objectives:

• Investigate the incorporationof triaxial testing into the mix design procedure. Shearparameters reliably define the performance properties ofcold mixes, but standardised(simple) procedures need tobe developed to meet theneeds of both research andcommercial laboratory

84

Figure 2: Structure of the Project

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mo

C6

00

2 ylr

ae

Phase 1: Inception study

• Obtain available performance data on pavementsincorporating bituminous stabilised materials (BSM);

• Review existing tests and protocols related to mix designon BSM;

• Formulate approach and detailed planning for Phase 2.

Phase 2: Develop new methods as needed

• Develop pavement design and materials classificationmethods based on LTPP and APT data;

• Refine existing laboratory tests and develop new tests asneeded to facilitate mix design and classification of BSMstability and flexibility.

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Phase 3: Compile guidelines

• Incorporate new methods and practices for Mix Designand Structural Design from Phase 2;

• Review and expand sections related to construction,materials selection and composition;

• Review and publish.

operations, as well as toadvance an understanding ofthe relationship betweenmonotonic versus dynamicproperties of cold mixtures;

• Develop more realistic andreliable specimen preparation and conditioning protocols,especially with respect tocompaction and curing.Cognisance needs to be taken of, for example, binder type,aggregate type and activefiller content;

• Identify a durability test forincorporation into the mixdesign procedure. In thebroad sense, durability covers binder durability as well asmix durability (especiallymoisture damage). CurrentTensile Strength Retained(TSR) tests in the ITS modedo not provide sufficientlyreliable simulation ofmoisture damage;

• Identify a reliable and robustclassification system foremulsion and foamedbitumen treated materialsthat could be used forpavement design purposes.Although a unified systemthat would be generic for allcold mixes would bepreferred, key differentiatorsmay need to be incorporatedto distinguish between thematerials if this is notpossible.

Given the scope of theseobjectives, data on a wide rangeof mixes has already beengathered and synthesised in adatabase under several differentheadings, including mechanicaltesting (shear properties, resilient

properties and permanentdeformation), flexural testing(strain-at-break, flexural stiffnessand fatigue), curing, durability(moisture susceptibility and binder ageing) and compaction.

Laboratory and field research(using trial sections) will continuein 2007 to develop and calibraterevised and new procedures forthe mix design of emulsion andfoamed bitumen treated mixtures.Although some of the monitoringof field trials will continue through2008, by early in that year it isplanned that sufficient findings will be available to incorporate into the new guideline.

Structural designdevelopments

The aim of the structural designcomponent of the project is toprovide a practical, reliable andvalidated methodology fordetermining the structural capacity of pavements that incorporatebituminous stabilised layers. Atthe outset, it was recognised thatsuch a method would require asignificant knowledge base related to the construction andperformance of pavements thatincorporate BSM. A comprehensive search and analysis task istherefore being conducted toobtain and document data relating to the performance of BSMpavements under long term fieldloading conditions, as well asunder Heavy Vehicle Simulator(HVS) testing.

To date, the available construction and long term field performanceinformation for 17 BSM pavement

85

sections has been compiled anddocumented, with a further sixsections under investigation. Datahas also been obtained andsummarised for seven BSMpavements that were tested withthe HVS. These seven pavementsprovide a total of 22 configura-tions tested under differentloading intensities. The combinedperformance database will be used to construct a knowledge basewhich will be used to calibrate and validate the pavement designmethod for BSM pavements.

The structural design method willincorporate the best elements ofmechanistic design, coupled with a strong empirical component thatwill be determined by thepavement performance database.The mechanisticdesign element willinclude a basicassessment tocheck thatpavement balanceand subgrade strain requirements aresatisfied. Weakerelements ofmechanistic design– such as theuncertaintyassociated withassumed layer stiffness – will beaddressed through the use of amaterials classification systemwhich will provide detailedguidelines on how to classifymaterials based on indicator tests.The material classificationassigned to different layers willthen be used to obtain appro-priate, predefined modular ratios

for each layer, which in turn canbe used to obtain realistic andsituation-specific stiffnesses foreach material class.

Pilot test

To date, the basic methodologiesof the pavement design andmaterials classification systemshave been completed. It isenvisaged that a trial version ofthe design method will be pilot-tested during 2007. This testingwill be performed by selectedpractitioners, and feedback will beused to refine the method foroptimal accuracy and robustness.

It should also be noted that,during 2006, the CSIR developeda long term research plan for an

updated,generalisedpavement designmethod for SouthAfrica.

This project wasinitiated by theSouth AfricanNational RoadsAgency Ltd(SANRAL), and willaddress many ofthe deficiencies of

the current mechanistic designmethod.

Discussions will continue to ensure that the outcome of the structuraldesign method for bitumenstabilised materials willcomplement the SANRAL initiative, which has a broader and longerterm objective. q

86

The aim is to

provide a practical,

reliable and

validated

methodology for

determining

structural capacity

87

Contractors in SouthAfrica, Australia andelsewhere have achieved

optimum pavement perform-ance when mixing and placinghot and warm asphalt, evenunder conditions of inclementweather and extended timeand haul distance, through theuse of bitumen modified withFischer-Tropsch wax.

Wax modifiers (commonly referred to as Sasobit® or FT wax) areproduced by Sasol Wax (a division of Sasol Chemical Industries Ltd.)using the Fischer-Tropsch catalytic process utilising natural gas. FTwax is fundamentally differentfrom naturally occurring waxes inbitumen, in that it is inert tochemical and ultraviolet activation. It further combines a low meltviscosity with a reduction inpenetration and an increasedsoftening point of the modifiedbinder.

The physical and rheologicalproperties of FT wax have asignificant impact on those of thebase binder at low modificationlevels. These are evident in theimproved blending, compactionand ease of laying of the modifiedasphalt and the resultantperformance characteristics of thepavement.

Physical properties of FT wax

Pure FT wax begins to crystalliseabove 1000C. However, practicalexperience has shown that asphalt mixes containing this modifier canbe compacted at temperatures aslow as 800C, which seems tocontradict the first statement. This raises the question of themechanism of FT wax crystall-isation in asphalt mixes, since thishas a considerable influence onthe minimum temperatures of

88

Fischer-Tropsch wax bitumen modifier:

Overcoming temperature andtime constraints

Francois Bornmann

Marketing ManagerSasol Wax

Robbie Hiley

Marketing ManagerSasol Wax Australia (Pty) Ltd

Stefan Strydom

Business ManagerSasol Wax

asphalt paving and rolling, and itsefficacy as a warm mix additive.

A DSC (Differential ScanningCalorimetry)1 investigation showsthat the crystallisation onsettemperature of the modifier inasphalt hot mixes depends on itsconcentration and on the coolingrate of the mat. Under realisticcircumstances (3 % FT wax in the

binder and 2°C/min cooling rate) it begins to crystallise around 85°C.

This implies a viscosity reducingeffect down to this temperaturelevel. Constraints regarding themix workability are not expectedsince the rolling of hot mix asphalt – and even of warm mix asphalt –is usually completed above 85°C.

89

Figure 1: Influence of Sasobit on bitumen viscosity

Viscosity

The significant influence of FT wax on bitumen viscosity is shown inFigure 1.FT wax-modified asphalt exhibitsthe anomaly of increasedresistance to permanent deform-ation in the service temperaturerange, while promoting workability through lower binder viscosity inthe mixing/paving range oftemperatures.

The presence of a dense lattice ofhydrocarbon wax crystals causes a restriction to flow of a “softening”binder mass at elevatedtemperature under the influence of heavy axle loads, while the meltcharacteristic of the wax isshowing the same kinetic delaywith a resultant higher melt pointand no detrimental effect onbinder viscosity.

Physical properties ofmodified binder

Increasing percentages of FT waxwere added to 80/100 penetration

grade bitumen to illustrate theeffect on various binderproperties. These are depicted inFigure 2.

Both design engineers andcontractors can use these effectsto meet a particular desiredoutcome where, for instance, longhaul distances, short road closurewindows and poor weatherconditions pose a threat to a highquality finished pavement.

Case Studies

The case studies belowdemonstrate how the uniqueproperties of FT wax-modifiedasphalt can be utilised toovercome severe conditions oflong hauls, narrow constructionwindows and low ambienttemperatures to provide a durablepavement in the rehabilitation ofhighly trafficked roads2,3. Heavy traffic in major global citiesnow increasingly requires thatroutine maintenance of importantarteries be carried out within avery short space of time2. Labour

90

Figure 2: Effect of increasing Sasobit content

intensive and time consumingprojects such as deep patchmaintenance are even moretroublesome.

A deep patch maintenance projectin Sydney, Australia, required that a stretch of road pavement 67meters long, approximately400mm deep and 3 meters widebe removed, profiled and repavedin four layers within 9 hours —working at night, in the middle ofwinter. No rutting was to beobserved the next morning orshortly thereafter as a result ofelevated asphalt temperatures.The road carries a traffic loading of approximately 60 000 vehicles/day, and road authorityspecifications on compaction, ridequality etc. had to be met.

Projectrequirements

The projectrequirements couldonly be achieved by producing anddelivering “warmmix” asphalt to site, and laying it atconsiderably lowertemperatures thannormal. This was achieved bymodifying the bitumen with FTwax at 1.5% of the bindercontent.

The project started at 20h30 withthe profiling and removing of theold asphalt and base layers. Oncethe area had been cleaned,200mm of stabilised base wascompacted into the affected areaand finished to ensure that exactlevels were attained. This process

lasted until approximately 00h30,by which time the ambienttemperature had dropped to 100C. Wind chill effects made workability and effective compaction evenmore difficult.

The asphalt was to be laid in twobase layers of 60mm each, andtwo wearing course layers of45mm each. The 60mm baselayers were produced at 1300C,and the two top layers at 1400C.Paving of the first layer began atapproximately 00h45. In additionto the low paving temperatures,the paver burners were alsolimited to 1200C to minimiseintroduction of any extra heat intothe system.

Temperature probes were inserted into the core ofeach asphalt layerto measurevariations in thetemperature of each mat throughout thewhole process. Theprobes were placedin the middle ofeach layer (probe 1in the bottom and 4 in the top layers)and not directly ontop of each other to

make sure that the wires were not cut during the rolling. Thetemperature increase is due to the subsequent layers being deposited on top of the underlyinglayers.The detailed temperatureprofiles in Figure 3 show the corestart temperatures and the timeframes taken to finish all fourlayers.

91

No extraordinary

precautions

were taken

during the

paving or

compaction

processes

In each case cores were takenimmediately before the next layerwas laid on top of it, and thesewere analysed specifically forcompaction. During the wholeprocess the paving temperaturesin the back of the paver variedbetween 110 and 1250C.Construction of the pavement wasfinished at approximately 04h30(including the coring of the lastlayer), and the road was openedto traffic immediately.

No extraordinary precautions were taken in the paving or compactionprocesses. No dragging of thepaver or the appearance of a“bony” mix, typical of paving atthese temperatures, wasobserved. There were also noproblems experienced with handraking of the edges of the topmat. Joints with the existingpavement were smooth and tight,and all building specifications were met.

Long haul in NSW

Broken Hill is a town close to theNSW border with South Australia,

approximately 550 kilometresfrom Adelaide and 760 kilometresfrom Dubbo. There are no asphaltplants near Broken Hill, and if aminor or medium sized pavingproject is undertaken, asphaltmust be trucked over these vastdistances. This results in haulagetimes of up to 10 hours or more,depending on traffic conditions.The alternative is concrete pavingwhich is not always an option dueto unstable road substrates andheavy mining vehicles.

Unless a mobile plant is used, theasphalt is normally heated up toinordinately high temperatures (as high as 1850C) and then is laidonly during the very hot months –effectively December to January.Any small abnormality in theweather causes huge problemsand the window for pavementconstruction or repair could shrinkconsiderably.

When the asphalt arrives on site it is often extremely difficult to workdue to large heat loss sufferedduring transport. If there are any

92

Figure 3: Layer temperature profile

delays because of traffic diversionor pre-laying preparation of theroad, the asphalt is often unusable when the time comes for it to belaid. The road authority frequentlyhas to allow for losses of up to10% – even in the very warmmonths.

The trial asphalt wasmanufactured with a 320 viscositygrade bitumen (similar topenetration grade 40/60),modified with 1.5% FT wax, andwas loaded into the trucks at1800C. It was covered using aheat shield sheet laid over the topof the asphalt, together with three layers of carpet under-felt, andfinally the usual tarpaulin covers.

The first truck arrived atapproximately10h30 after a 9.5hour drive. Onarrival the asphalttemperatures at the side walls were aslow as 1120C, whilethe surface andcore temperatureswere in the regionof 1300C and1600C, respectively. Although the trialwas planned for avery hot day it had rained the daybefore, and the ambienttemperature was only 240C in themorning.

The road was profiled and cleaned, and paving then began as usualwith a 25mm layer. During thelaying operation the temperatureof the asphalt dropped to 1000Con the sides of the paver (surfacetemperature), with the

temperature in the middle being in the region of 1350C. The ambienttemperature at this time wasabout 300C. After the asphalt had been laid the edges were hand-worked tosmooth them off, and a vibratoryroller was used to compact theasphalt. Once the road hadreached a surface temperature inthe region of 650C, a 17 tonpneumatic roller was used with acoverage of 6 passes to completethe compaction. The road surfacetemperature after finishing wasapproximately 450C. After a fewminutes the road was opened totraffic and the other half of theroad was tackled. Total elapsedtime from profiling until the roadwas opened to traffic was 2.75

hours.

The second truckcarrying the nexttwo loads of asphalt had been waitingfor a few hours,resulting in a totaltransit time ofapproximately 12hours before theasphalt was loadedinto the paver. Thisasphalt temperature

in the truck had reached as low as 1000C near the side walls, and was 1150C and 1350C at the surfaceand core respectively.Construction proceeded as withthe previous lane, and only a fewlumps of asphalt (150 kg) werefound to be unusable.

In the cases mentioned above, the asphalt was laid as if in closeproximity to the plant, and was

93

Total haulage

times of up to

12 hours

before the

asphalt could

be loaded into

the paver

easily formed and shaped wherenecessary. To date no problemshave been noted with thepavement, and no subsequentrutting or movement of theasphalt has been observed.Also no “slumping” and bleeding of the mix in transit was observed as was normally the case with theselong haulage paving projects. Thisfeature resulted in real savings asbleeding would have damaged theinsulating materials.

It was evident that the roadauthority had widened the working window of asphalt in Broken Hillby another four months, which has “paved the way” for an extendedprogramme next year. The trialwas an outstandingsuccess, with boththe subcontractorand the roadauthority impressed by the performanceof the FTwax-modifiedasphalt.

Boral Asphalt notedthat FT waxmodificationprovides a practicaland economicalmeans ofsignificantlyincreasing the range of productsavailable from our regional asphalt plants, while still providing aquality product for the client.

Durban freeways

The Southern and WesternFreeways of the Durban Metropolis both carry heavy traffic loadsoffering very little opportunity for

road closures. Work on theSouthern Freeway Phase 2 and 3,as well as on the Western Freeway Phase 1 and 2, recently benefitedfrom the use of FT wax modifier.

The project team had greatdifficulties with thin surfacing work (25 mm wearing course)scheduled to be laid at night inconditions falling ambienttemperatures as winterapproached. It proved impossibleto meet the asphalt specificationsusing the specified modified binder within the allowed constructionwindow, as only day time work onSundays produced satisfactoryresults.

Penalties

The impendingpenalties for delaysprompted thesupplier, NationalAsphalt, to use their extensiveexperience with FTwax to persuade the client to allow a trial section with thismodifier. Theresults showed thatwork could be

carried out at night and duringwinter time since the addition ofFT wax lowered the mixing andcompaction temperature by 200Cmore than would have beenpossible using the specifiedmodified asphalt.

The client approved the use of FTwax for the remainder of theprojects.

94

The addition of

FT wax lowered

the mixing and

compaction

temperature

by 200C more

than would

otherwise have

been possible

A total of 95 000 tons of FTwax-modified asphalt was laidwithout a single failure, working at night in adverse winter conditionsand with minimal disruption oftraffic.

Storage stability

It was noted by National Asphaltthat FT wax modifier is easilyblended and yields long storagestability. Due to the lower mixingtemperatures required, energysavings were also realised, and anextended construction window was achieved as a result of thereduced temperature at which thedesired compaction could beachieved.

References

1 – Dr. T. Butz: Laboratoryreport. Sasol Wax, 20062 – Dawie Erasmus, Vela VKE:Night time rehabilitation of theSouthern Freeway (M4) Durban –Civil Engineering, July 2005, Vol.13, No. 7, 3. 3 – Ingenuity solves surfacingproblem – Modern Asphalts,February 2006

Acknowledgements

The authors extend their gratitude to J Figueroa, S Yin and C Brady of the RTA NSW Australia,G.Hennessey, R.Crabb andJ.Burton of Boral Asphalt,Australia, and to Wynand Nortje of National Asphalt, South Africa, fortheir valued input. q

95

Sourcing and introducing appropriate andinnovative solutions to

the South African roadindustry is one of thehallmarks of industryleadership. The recent adventof a high tech, singlepass, surface dressingmachine by Tarfix (Pty)Ltd now offers a widearray of new possibilitiesin road surface seals.

Developed in France, andnow used internationally, this new method of roadsurfacing allows for thesimultaneous application ofthe binder and the aggregate in a single pass. Incomparing this method withthe traditional two passsystem, it soon becomesvery apparent that the latterhas a number of inherentlimitations which areovercome when using thesingle pass system.

Figure 1 highlights the majortechnical differences between thetwo systems, of which the mostnotable is the variability in thetime between the contact of thestone with the binder in theconventional system.

96

Achieving cost-efficiency through technology:

Advantages of SA's new singlepass surface dressing machine

Deon Pagel

Marketing ManagerTarfix (Pty) Ltd

Figure 1

The Chipsealer units are fullyimported from Secmair in France.The South African units boast themost advanced technology everinstalled on this type ofequipment, and includes threeon-board computers, which control all aspects of the binder andaggregate application, as well asmonitoring all the relevantphysical environmental data (suchas road temperature, airtemperature, positioning etc.) and recording the application onvideo.

In the international arena the useof the single pass system has hada major impact on the traditionalsealing market, and specifically on the effectiveness of maintenanceseals, leading to a zero potholescenario. It is believed that theintroduction of this equipment into the South African market willassist road owners to moreeffectively maintain their roadnetworks and reduce annualmaintenance costs.

In addition the accurate sprayingof the binder (temperature control

andapplicationrate) inaccordancewithspecifications,(which isnormallydifficult toachieve inpracticalterms onsite,) shouldgreatlyimprove theeffectiveness

of surface seals.

The use of visual imagingequipment and integratedcomputer controls on the newSecmair equipment offers roadowners an alternative that was not previously available to them – i.e.the option of applying a low costmaintenance seal over just thatportion of road that really needstreatment.

Emulsion binders

The units are designed to apply all types of binders, includingmodified binders, requiring anapplication temperature of up to1700C. International trends showthat the future of these units lieswith the application of emulsionand modified emulsion binders.

The environmental and safetyaspects associated with emulsions, together with the ease ofapplication and the reduction inenergy consumption (LP gas inparticular), makes emulsions avery attractive option.

97

Figure 2: The Chipsealer 61 unit with 3 500 l binder tank and behind it the 8.5m3 stone hopper

Graded stone seals

The seals that are being proposedas generic low cost holding actions on a road are typically made up ofa modified emulsion binder,combined with a “slightly” gradedstone aggregate, such as acombination of a 6.7 and 9.5mmstone, or even a 4.75 and 6.7mmstone. The graded effect of thestone aggregate, together with the

low viscosity of the emulsion to fill the cracks, achieves a result thatis not obtainable with conventional surfacing systems (see figure 3).

Conventional seals

Apart from their ability to applygraded stone seals, the machinescan be used for any of thecommonly known single or doubleseals using up to 19mm sizedaggregates and conventional ormodified binders.

Since the arrival of their first unittwo months ago, a range of seals

totalling in excess of a 100,000 m2

have already been completed.These applications varied fromemulsion single and double seals,(also using latex modifiedemulsions) on municipal roadnetworks, as well as 80/100penetration grade double seals.

While the on board computerscontrol the binder temperatureand maintain the application ratesof binder and aggregates within

tight tolerances,(while digitallyrecording the roadcondition beforeand afterapplication), thereare also a numberof other practicalaspects whichmake surfacingwith these unitsadvantageousvis-à-visconventionalchip-and-spraytechniques,namely:

• Minimal aggregate loss in theearly life of the seal due toinstantaneous applicationwith the binder;

• Cost-effective sealing ofroads requiring remedialtreatment on distressed areas only;

• Reduced traffic disruption due to fewer construction vehicles on the work site;

• More versatile and suitablefor sealing restricted areasdue to the highmanoeuverability, forexample at intersections;

98

Figure 3: Efficient use of graded stone and emulsionbinder for sealing cracks

• Self contained and minimalsite establishment, whichfacilitates a quick responsetimes.

Quality issues

Very few people realise howquickly the temperature of abituminous binder drops once itmakes contact with the roadsurface. It is exactly thisoccurrence that puts the singlepass system way ahead of theconventional or traditional twostage system in terms of quality.

Figure 5 illustrateshow the ‘wetting’ ofmetal balls isaffected whenmaking contact withbitumen at differenttime delays. The ballat the top left is very clearly bestsubmerged, just twominutes after making almost immediatecontact with thebinder, i.e. as perthe single passsystem. The ball topright was broughtinto contact with the

exact same binder – inthis case only after aninitial delay of 30seconds. It can clearlybe seen that after 2minutes the ball hasmade far less contactwith the binder. Thisillustrates theimportance ofobtaining the correctbinder viscosity if good adhesion of the

aggregate to the binder is to beachieved.

The diagram also illustrates thatthe temperature of a binder, evenif applied as hot as 1700C, willreach the ambient roadtemperature about two minutesafter application. This clearlyproves that any delays in thestone reaching the binder willdefinitely result in inferioradhesion, and very likely instripping of the aggregate – aphenomenon often seen on ourroads.

99

Figure 4: Maintenance seals can be appliedselectively while the unit is driving over the road

Figure 5: How the ‘wetting’ of metal balls is affected when making contact with bitumen at different time delays.

100

Figure 6 illustrates how the stone applicationimmediately followsthat of the binder.

Production andlogistics

Production dependslargely on the type ofseal being constructedand on the sitelogistics, but can varybetween 5,000 to13,000m2 per day. Thelatter figure wasachieved locally whileconstructing a single seal using an emulsion binder, but largermachines will be made available in time to come, and for thosecontractors who are interested inhigh production, there are unitsavailable that capable of up to75,000m2 per day.

The objective is, however, toconcentrate on the maintenanceseals for local authorities, and also to offer a service to any contractor who wants a seal of between5,000 and 30,000m2 done in a

very short time, without having toengage in huge and cumbersomesite establishment.

The second surface dressingmachine is expected to arrive inSouth Africa in February 2007,offering a new and unique serviceto the roads industry as a whole.

For any enquiries please contactDeon Pagel at 011-708 4794, (cell 083 306 9774) or on e-mail:deon@tarfix.co.za q

Figure 6: Stone aggregate being applied one secondafter the binder application

102

To secure the position ofhot mix asphalt wearingcourse as a cost-effective

road layer, a re-examination of design procedures isnecessary, especially to ensure that mix components arebalanced to resist topermanent deformation whilenot compromising thedurability of the layers.

Following a recent forensic studyby CSIR Built Environment onbehalf of the Gauteng Department of Public Transport, Roads andWorks (GPTRW), it was evidentthat a cooperative effort involvingclient bodies, consultants and theasphalt industry should belaunched to redress the issue ofpremature road distress,especially at busy intersections.Over and above the need toensure that structural designprocedures are sound and basedon relevant traffic data, mixdesign procedures should exploitavailable technology to designhigh performance mixesconsistently, and to incorporate

these principles into the regularlyused production mixes in Gautengto ensure that optimal asphaltmixtures render satisfactoryperformance and meet clients’expectations.

Background

The development of rut-resistantmixes goes back to 2003, whenArcus Gibb and Much Asphaltundertook a contract at the ORTambo International Airport(ORTIA), and since then methodshave been continuously improved.

Initially it was planned to usequartzite aggregate, but due tolarge volume requirements for thecombined runway and majortaxiways contract it was decidedto use dolerite, available in largerquantities. The high design trafficclass and 50mm thickness of theoverlay called for asphalt withslightly larger aggregate than theCOLTO continuously graded(medium sized). With this gradingbeing effectively a 26.5mm typesuitable for asphalt base, it was

Focus on deformation resistance:

Innovative design methods forHMA in Gauteng

Herman Marais

Technical ManagerMuch Asphalt (Pty) LtdGauteng

Derick Pretorius

DirectorArcus Gibb (Pty) Ltd

decided rather to use the old TRH8 coarse envelope (13mm nominalaggregate type). The first contract where the dolerite TRH8 coarsemix was used successfully was the ORTIA Echo taxiway contract. Onthe following ORTIA contract(Yankee taxiway) the gradingadopted was slightly finer on the2.36mm sieve, which resulted inlower gyratory voids and higherMMLS3 rutting values.

Subsequently, to ensurecompliance with more stringent

performance-related specific-ations, it was decided to revertback to the original Echo taxiwaycontract grading with only slightchanges to optimise the mix.These included adjustments in thegrading to maintain VMA values inthe region of 16, which satisfy therut criteria without causing binderstarvation of the mix, i.e. main-taining a film thickness of 7.5µm.With the very high volume of work that had to be completed beforethe end of 2006, it was decided toprepare a quartzite design as a

103

Performance required Fundamental mix property Simulation testingto confirm

performance

• Mix 1: Highly trafficked (>ES10) wearing course:

• High rut resistanceand durability;

• Acceptable fatigueresistance;

• Acceptable friction (nofattening/bleeding).

• Grading to be a 13.2mm nominal aggregate, coarse graded type to ensure compactability; 2.36mmkey compositional point to be set to ensure VMA target obtained;filler set to obtain a filler/binder(F/B) ratio of ≈ 1.3. The gradingcurve to be smooth to ensurecompactability and preventsegregation;

• % passing 0.075mm (filler) to be relatively high to stiffen mix (F/B ≈ 1.3 – 1.45);

• Adequate VMA to get enoughbinder in (for durability/fatigue)while still preventing closing upof the mix (i.e. Marshall voids =5.0 and terminal voids in SPgyratory >3%);

• Binder penetration – 60/70 -40/50 Pen;

• Film thickness > 7.5µm(minimum binder content of4.5%)

• MMLS3 @ 50°Con briquette/fieldcores;

• Mod Lottman;

• 4 Pt beam fatigue test @ 200µmand 350µm;

• Gyratory curve to 300 gyrations.

Mix 2: Highly trafficked (>ES10) wearing course for high shear intersectionareas:

• Very high rutresistance anddurability;

• Acceptable fatigueresistance;

• Acceptable friction (nofattening/bleeding)

• As above with binder type to be40/50 Pen. and F/B slightlyhigher (±1.40) with filmthickness > 7µm

As above

Table 1: Fundamental Design Principals

backup wearing course in theevent of dolerite aggregatebecoming unavailable during thecontract. It also provided the ideal opportunity to develop the mixwith quartzite aggregate as part of the preparation of the GPTRW rutresistance mixes.

Design methodology

(a) Fundamental designmethodology

The fundamental principles ofcompositional and volumetricasphalt design 1) 2) 3), as developed on various high performancepavement structures since 2001are shown in Table 1 and wereused to obtain specificperformance properties for thesemixes.

The compositional and volumetricdesign methodology adoptedutilises the following processes toarrive at optional mixes inaccordance with targetperformance requirements:

• Best aggregate sources interms of desired aggregateproperties (e.g. shape,i.e.cubical to slightly flaky;hardness according to COLTO criteria; consistency) areused;

• Initial grading is optimised for 50mm thickness, startingwith a selected or specifiednominal aggregate size(13.2mm) and filler to yieldfiller/binder ratio in theregion of 1.3, and thein-between points on thegrading log curve smoothed.Also the fraction passing the

2.36mm screen (primarycontrol sieve) is set at a level that ensures a “coarsegraded” mix more or lesscoinciding with the coarseboundary of the conventionalgrading envelope;

• Aggregate proportioning iscarried out to meet the target grading;

• Marshall volumetric design isthen carried out to checkVMA, VIM and binder/filmthickness relationships;

• The proportion passing the2.36mm screen is thenadjusted to modify the VMAuntil volumetric requirements are met. It was noted that a2.5% reduction in thepercentage passing the2.36mm screen generallyresulted in a 1% increase inVMA (at the same binder andfiller contents);

• VMA is then adjusted, untilbinder film thickness, VIM’s,and gyratory voids meetvolumetric/compositionaltargets. The aim is always toarrive at a cost-effective mix, by adopting the minimumbinder content (or VMA forthat matter) that will satisfydurability and fatigue criteria;

• Performance tests are thencarried out followed, ifnecessary, by a process ofiteration until performancecriteria are met.

(b) Verification with other mixdesign methodologies

(i) PRADO

The implementation of the Belgian Road Research Centre

104

recommendations (R69/97 forbituminous mix design) involvesan analytical study prior toverification by mechanical testing.This analytical study is supportedby a software package calledPRADO (Programmes for AsphaltMix Design and Optimisation).

This method aims to achieve thebest possible compromise between various (and sometimesconflicting) requirements such asdealing with both resistance tofatigue and rutting of the mix. In

this approach, the stability of themix can be ensured by making use of intergranular friction whileavoiding overfilling the mineralskeleton with mastic (i.e. withfiller and binder). This masticshould only fill part of the voids inthe mineral aggregate and shouldalso have the right consistency(i.e. the correct proportion of fillerand binder).

Volumetric and masticevaluation of dolerite andquartzite mixes:

Theoretical volumetric calculations using PRADO software were donefor both the designs incorporatingboth dolerite and quartzite. Theresults of the volumetric analysis(estimating VIM, VMA and thefiller/binder ratio - by both massand volume – and the stiffeningeffect of the mastic) over a rangeof binder contents were calculatedas follows:

Dolerite aggregate evaluationresults

In general the estimated VIM andVMA values as predicted byPRADO are slightly higher than the values obtained in the laboratory.

From Table 2 it can be seen thatthe increase in the Ring & Balltemperature of the mastic

105

Dolerite Quartzite

Binder content (%)

Estimated VIM (%)PRADO

VIM (%) laboratory

Estimated VMA (%)PRADO

VMA (%) laboratory

Filler/binder ratio (bymass)

Filler/binder ratio (byvolume)

TR&B increase (mastic vsbinder)

4

7.7

7.7

17.1

17.5

1.4

0.49

11.9

4.5

6.5

5.4

17.1

16.7

1.24

0.44

10

5

5.3

4.0

17.1

16.5

1.12

0.39

8.7

5.5

4.1

3.6

17.1

17.4

1.02

0.36

7.7

4

6.2

6.8

15.3

15.7

15.9

0.60

21.7

4.5

5.1

4.9

15.3

15.1

1.41

0.53

17.4

5

4.0

3.2

15.3

14.7

12.7

0.48

14.6

5.5

2.9

1.5

15.3

14.4

1.16

0.43

12.5

Table 2: PRADO Mix Design Estimates Versus Actual Volumes

compared to the pure bitumen forthe dolerite mix, falls below therecommended range of 12 – 16°C. This would imply that the mix istender, soft and relative easy toplace and compact, whileresistance to permanentdeformation during the service lifemight be reduced. The fatigueresistance, however, should begood.

Quartzite aggregate evaluation results

In general the estimated VIM andVMA values, as predicted withPRADO, are slightly higher thanthe actual values obtained.

The increase in the ring and ballsoft point temp (TR&B) of thequartzite mix at the design binder

content of 4.7% is 16.8ºC, whichis above the upper recommendedlimit. This indicates that difficulties may arise with the compactabilityand workability of the mix.However, it may also have apositive effect on the deformationresistance of the mix provideddurability is adequate and fatigueresistance within specifications.

(ii) Bailey Method

The Bailey Method of gradationevaluation focuses on theaggregate properties that affectthe way aggregates fit together(or pack) in a confined space orvolume (See Figure 1). To analyse the packing factors, the methoddefines four key principles thatbreak down the overall combinedaggregate blend into four distinct

106

Figure 1: Bailey Method Mix Composition Principals

compositional fractions (See Table4). Each fraction is then analysedfor its contribution to the overallmix volumetrics.

By comparing the size of particlesthat fit into the voids between thelargest aggregate pieces, and thesize of the largest aggregatepieces found in a fraction, ratioscan be developed that are anindication of how well all theparticles in the fraction fit together and what the mix characteristicswill be like. The Bailey Method can be used to predict how changes inthe factors that affect packing willchange the resultant volumetrics,compactability and segregationpotential of a particular mixture.See Table 3 for packing factors,which vary from mix to mix.

Principles of the BaileyMethod:

Four principles are adopted in themethod:

• Principle 1: Determines thebreak between coarse andfine aggregates. From this itis established which particlescreate voids and which onesfill them and which fraction(coarse or fine) is in control;

• Principle 2: Evaluates thecoarse fraction and how theparticle sizes in the coarsefraction pack together, andhow this influences thepacking of the fine fraction.(The volume of voids in thecoarse aggregate, coursefraction compactability andsegregation susceptibility arealso appraised.);

• Principle 3: Evaluates thepacking of the overall finefraction in the combinedblend;

• Principle 4: Evaluates thepacking of the fine part of the fine fraction.

All four principles of the BaileyMethod are interactive and mustbe monitored for changes. If a

gradation changes, then all fourprincipals must be reviewed.

Evaluation of Dolerite andQuartzite mixes with BaileyMethod:

The dolerite and quartzite mixeswere evaluated with the fourBailey principles, and the resultsare given in Table 4.The dolerite mix, somewherebetween coarse and fine (more

107

Gradings Shape

Continuously graded Flat and elongated

Gap graded Cubical or round

Compactive effort Surface texture

Type = static, impact, shearing Smooth

Amount = field vs laboratory Rough

Strength Size

Individual aggregate toughness Nominated max. particle size

Table 3: Properties that influence mix packing and end compaction

coarse) graded, may beproblematic as far as the BaileyMethod is concerned, as thecoarse and fine fractions could bestruggling for control of thevolumetric properties. The CARatio used is slightly higher thanthe upper acceptable limitsuggested, which could indicatepossible compaction problems inthe field. The FAc ratio is within the acceptable limits, but the FAf ratiois slightly higher than thesuggested upper limit which would indicate high mortar stiffness (asintended in the design fordeformation resistance in thefundamental design methodology . This is contradictory to the PRADO analysis of the mix, whichindicates a tender mix. Large

quantities of this mix have beenpaved in Gauteng with nosignificant compaction problems(including various ORTIAapplications over last three years).

The quartzite mix is“coarse-graded” and the coarseaggregate is therefore in control of the volumetric properties. The CAratio is higher than the upperacceptable limit suggested, whichcould indicate possible compaction problems in the field. The FAc ratio is within the acceptable limits, butthe FAf ratio is higher than thesuggested upper limit, whichwould indicate high mortarstiffness (as intended in the design to ensure good rut resistance).This is in agreement with the

108

Ratio Principle Dolerite Quartzite Acceptablerange

Effect if ratiosoutside

recommendedranges

CA Ratio 1 92.7 97.5 <85 for finegraded,

95-105 forcoarsegraded

Dolerite is between a coarse and finegraded mix (morecoarse than fine).

Quartzite is acoarse graded mix

CA Ratio 2 0.661 0.836 0.5 – 0.65 Overly high valuescan be difficult to

compact in thefield and can cause

“tenderness”because the coarse fraction does notwant to lock up

FAc Ratio 3 0.399 0.443 0.35 – 0.50 OK

FAf Ratio 4 0.516 0.529 0.35 – 0.50 High valuesgenerally indicatemixes with highdust to effectivebinder ratios and

high mortarstiffness

Table 4: Results of Bailey Principals Evaluations

Note: It is important to note that the suggested ranges for the Bailey Method ratios are not specifications, but guideline

only. Consequently they can be relaxed, preferably in conjunction with experience and engineering judgement.

PRADO analysis. Large quantitiesof this mix have been placed atthe ORTIA with no significantcompaction problems; thecompaction procedures were,however, thorough, with layerthickness at 40mm and above.

(c) Verification with perfor-mance related properties (i.e.original mix specification)

Various performance relatedproperties were defined to ensurefield performance requirementswould be met. The results of thefine-tuned mixes to be used in the Gautrans Challenge are listed inTable 5.

Field performance to date

The dolerite alternative for theintersection mix (40/50 penbinder) was used in three airport

pavement contracts over the pasttwo to three years. Extracted fieldcore values confirmed satisfactoryfield MMLS values at less than 1.6mm rutting, and conformance with all other performance criteria; field performance to date has beengood, given the extremelyaggressive taxiway traffic (i.e. 22ton wheel loading; 1 400 kPa tyrepressure).

This design methodology andperformance criteria were used onvarious projects in the WesternCape (N7 rehabilitation, M5Rehabilitation, Cape TownInternational Airport (CTIA) majortaxiways rehabilitation, and inGauteng area (various airporttaxiway rehabilitation and roadsprojects). Assessment of thesemixes, on all these pavements,indicated satisfactory performance

109

Performancerequirements

Test type and parameters

used

Criteria set Performance value

Mix 1 Mix 2 Mix 1: WC forhighly traffickedroads

Mix 2: WC forhighly traffickedintersection

Quartzite Dolerite Quartzite Dolerite

Deformationresistance

MMLS onbriquettes at500C dry (oncores) (mm)

<1.8 <1.6 1.6 1.4 To betested

1.2(1.6)

Averagedeformation percycle in 2000 -3000 range ofDCT (µ)

<0.4 <0.35 0.12 N/T N/T 0.33

Gyratory voids at 300 repetitions(on a 5%Marshall VIMsvolumetricsetting

>2.7 >3.0 2.8 4.1 To betested

4.3

Durability Mod Lottman >80% >80% 85 90 N/T 84

Fatigue 4 Pt beamfatigue (at 200micron strain):reps to failure

>2 mil >2 mil To betested

To betested

N/T 3.2million

ITS (kPa) >1000 >1000 1 368 >1000 >1000 1222

Table 5: Performance Simulation Properties (Criteria and test values obtained)

testing results and very successful field performance to date.

Experience with this mix designmethodology goes back to CTIAtaxiway mixes placed in 2001/2.To date an equivalent 300 000 x22-ton wheel loadings (1 400 kPatyre pressures), or an equivalentof 250 million E80’s, was carriedwithout any deformation ordurability problems.

Previously, the conventional“middle of envelope” mixes utilised at the Much plant at Benoni(before 2003) showed MMLS

values of ±3 to 3.5mm rutting.After compositional modification in accordance with the fundamentaldesign methodology utilised in this study, this was changed (as listedabove) to high performance rutresistant mixes – however, it isstill “binder-rich” (due to goodVMA values in the region of 16%)and therefore still has good fatigue resistance and durability.

A full scale APT evaluation of trailsections of these mixes is plannedfor mid 2007 and an update ofthese results can then be reported to the industry. q

110

References:

1 F.J. Pretorius, K.J. Jenkins, F. Hugo,D. Vietze: Innovative Asphalt MixDesign and Construction : Case studies onCTI Airport and Kromboom Parkway.Paper presented at the 21st ARRB and 11th REAAA Conference, Cairns,Australia, 2003

2 K.J. Jenkins, F.J. Pretorius, F. Hugo,R. Carr: Asphalt Mix Design forCape Town International Airport usingscaled APT and other selected tests.

6th International RILEM Symposium onPerformance Testing and Evaluation ofBituminous Materials, PTEBM’03, Zurich,Switzerland, 2003

3 F.J. Pretorius, J.E. Grobler, J. Onraët:Development of a Fit-for-Purpose ProductPerformance Specification System forAsphalt Mixes. Paper presented atCAPSA'04, Sun City,South Africa, September 2004

As part of a drive by theGauteng Department ofPublic Transport, Roads

and Works (GPTRW) tore-examine a number ofunresolved issues associatedwith hot mix asphalt, a projectwas launched not only todefine these issues, but also to serve as a catalyst forsolutions to be sought jointlyby the asphalt industry andconsulting engineers.

The project incorporates forensicand laboratory studies to defineand, ultimately, redress premature distress of hot mix asphalt. Thisinitiative seeks to bring about acommon understanding of theissues at stake, a systematicresponse through innovativedesigns, and an acceleratedpavement testing programme(APT) to evaluate the variousproposals and to developstandards for hot mix asphalt over a range of operating conditions.

In the last few years severalincidents of unsatisfactory

performance of HMA have beenencountered on provincial roads in Gauteng. The poor performancewas manifested in excessivedeformation, especially atintersections, and prematurecracking. In many instances, theHMA design life reduced from 8-10 years to 4-6 years. Consequently,the financial viability of HMAbecame questionable.

Research

The GPTRW commissioned theCSIR Built Environment to develop an HMA research programme notonly to investigate the causes ofthis unsatisfactory performance,but also to address several otherunresolved issues associated withHMA, including:

• The need for reliable testprocedures and acceptancecriteria for the assessment ofpermanent deformation andfatigue;

• The need for reliable testmethods to assess thedurability of HMA; and

111

HMA research programme:

Forensic investigation intopremature distress in asphalt

Elzbieta Sadzik

Materials EngineerGauteng Department of Public Transport, Roads and Works

• The need to assess theimplications of contact stressmagnitudes and distributionson the performance of HMA.

An HMA research programme wasproposed consisting of:

• Desk-top studies; • Forensic investigations; • Laboratory studies; and• Accelerated Pavement

Testing (APT) involving boththe HVS and the MMLS.

Forensic investigation

The forensic investigation wasconducted in two phases, namelya preliminary and a detailedinvestigation. The purpose of thepreliminary investigation was to:

• Assess the quality of the mixdesigns in broad terms;

• Identify the differentiatingcharacteristics of good andpoor performing sections;

• Attempt to identify thecauses of the failures; and

• Identify sections for thedetailed forensic study.

The preliminary forensic studyconcluded that:

• Mix design needed to bebetter aligned with the design environment;

• More attention should bedevoted to aggregatepacking;

• More rut resistant mixesshould be selected forintersections; and

• Design protocols for SMAneeded to be developedand/or refined.

The objectives of the detailedforensic investigation were tobetter understand the typicalcharacteristics of good and poorperforming HMA mixes, and toidentify mix design aspects thatrequire further study in the HMAproject.

Detailed investigations wereconducted on several sections ofthe provincial road network whichwere classified as both good andpoor performers. As part of theseinvestigations, non-destructivetesting, such as FWD deflections,Dynamic Cone Penetrometer andseismic testing, were conducted,as well as laboratory tests oncores extracted from the sections.The forensic investigation included a range of stone mastic asphalt(SMA) mixes, mediumcontinuously graded mixes and abitumen rubber continuouslygraded asphalt mix.

112

Figure 1: A typical example of deformation (Courtesy of CSIR)

Conclusions

The following conclusions relatedto the mechanisms of failure weredrawn:

1. Permanent deformation:

• lack of proper support fromthe underlying structuralpavement layers or theexisting asphalt layer(s);

• lack of resistance topermanent deformation ofthe new asphalt overlay.

2. Cracking:

• prematureageing of thebinder wherethe asphaltlayers werefound to bepermeable;

• stripping anddisintegrationof old/newasphalt layersresulting in alack of support provided to the overlays.

During the forensic investigation,it also became apparent thatcurrent procedures to ensure thatonly approved mixes materialisedon site were not satisfactory andrequired urgent attention. Thesame applies to the recording of“as built” data.

Recommendations related to thedesign and performance of asphalt overlays included the following:

• The design of new asphaltoverlays should meet the

demands of the site where itwill be applied;

• Designs should be based onreliable traffic loadinginformation and not only onnominal traffic volumes;

• There is a need to developmixes that depend more onthe stone skeletons and lesson the binder stiffness for use on sites subjected to slowmoving traffic such as atintersections;

• More attention should be paid to the mechanisms of distress

of the existingpavement.

The following mainrecommendationswere made as aresult of theinvestigations:

• Asphalt andstructuraldesigns need tobe based onappropriaterehabilitationinvestigations;

• SMA design proceduresshould be reviewed;

• The Bailey Method should bevalidated for South Africanconditions and be used as anaid to optimise HMAaggregate packingcharacteristics and also as an aid to quality control.

Aggregate packing

As a part of a desk top study forthe forensic investigation, aninternational literature study wasconducted to identify new toolsthat could be used to improve the

113

Forensic study:

Mix design

needs to be

better aligned

with the

design

environment

aggregate structure of asphaltmixes. Grading characteristics ofHMA mixes investigated in theforensic study were analysed using the principles of the BaileyMethod, as well as relatedtechniques such as the DominantAggregate Size Range and thepermeability characteristics of themix.

Based on the limited number ofmixes studied, it would seem thatthese analysis techniques holdgood potential for South Africa.

Industry challenge

An intended APT study on durable, rut-resistant mixes submitted byindustry in response to a challenge issued by GPTRW has beenpreceded by meetings held withrepresentatives of Sabita members – asphalt suppliers, together withtheir advisers and contractors. Atthese meetings discussionscentred on problems encounteredin asphalt mix design, aggregatesupply logistics, consistentproduction and qualitymanagement processes.

A general conclusion was that theCOLTO specification for aggregategrading of asphalt mixes may nolonger predicate optimal aggregate packing given the currentaggregate shapes, and that othermethods e.g. Bailey or PRADOmay be more beneficial.

A key objective of this cooperative effort of GPTRW and industry is toencourage innovative thinkingwithout being restricted by current specifications.

The asphalt industry has acceptedthis challenge enthusiastically andhas come up with severalinteresting designs, which will beevaluated as part of the HVStesting programme (see page102). The innovative asphaltmixes included the following:

• Stone skeletal HMA used atairports;

• High Modulus Asphalt;• HMA mix designed according

to the Bailey Method; and• HMA mix manufactured with

chrome slag aggregates.

APT and laboratory study

APT and LTPP studies havecommenced on road P159/1 (R80) with the testing of a standardasphalt mix commonly used inGauteng. These studies, which are linked to an extensive laboratory

114

Figure 2: HVS with climatic chambertesting a standard mix

test programme, will seek todevelop appropriate test protocolsand acceptance criteria for theassessment of permanentdeformation of hot mix asphalt.The standard mix was constructedin three different layer thicknesses – 25mm, 40mm and 60mm – andthe APT testing will be performedat three different temperatures –400C, 500C and600C, using threedifferent loadingconditions. Futuretests will comparethe optimiseddesigns submittedby industry with the performance ofthese conventional“box standard”mixes.

This approach willcreate a betterunderstanding ofthe mechanismsassociated with permanentdeformation and will allowdesigners to consider site-specificconditions, such as climate, trafficloading and pavement structure,in their designs.

As good performance comprisesresistance to both rutting andcracking, as well as durability, allexperimental mixes will bemonitored over extended periodsof time to assess all theseperformance characteristics. It is anticipated that the APTtesting of the standard mix will becompleted by July 2007, after

which the resultswill be evaluated toformulaterecommendationsthat will ensureimprovements inboth the design ofasphalt, the designof rehabilitationactions, and qualitymanagement of hotmix asphalt.

More information on the forensic testingcan be found in theSummary Report:

Forensic Investigation into thePerformance of Hot Mix Asphaltno: CSIR/BE/IE/2006/0015/B by E. Denneman and E.J. vanAssen. q

115

This cooperative

effort of GPTRW

and industry

is to encourage

innovative thinking

without being

restricted

by current

specifications.

5

BestPractice

I've been a Capetonian formore than 60 years andyes, it is a great place to

live, work and play. I've beenhere so long, I could probablywrite a booklet entitled How to enjoy Cape Town withoutactually moving!

But what is it about the place thatmakes us feel and act differentlyfrom other areas – perhaps themountains and coast, the(unpredictable) weather,vineyards, sugarbirds, TweedeNuwe Jaar, the noon-day gun, thelaid-back attitude, the perceptionthat civilisation stops at SirLowry's Pass and all those otherstrange traditions that give thiscity its great character.

One of these that I find as exciting and enjoyable as visiting thedentist is paving the traditionalSABS asphalt mix normallyspecified for residential roads. This is:

• 25mm thick;• 13.2mm maximum size

stone;

• 5% bitumen(60/70 pen);

• 4.5% voids in the mix.

When only 25mm thick, theproportionally large size aggregate and voids in the mix value causethe mix to be:

• more difficult to compactthan need be;

• more permeable, thus putting the asphalt and base at risk;

• more difficult to get goodsurface finish with handwork.

Another fact not usually realised is that the compaction window of a25mm mat can range from as lowas:

• 6 or 7 minutes on a cold,windy day;

• only 13 or 14 minutes on ablinding hot, windless,summer day.

Enough time for rolling in coldweather? Enough time for placingby hand, then rolling?

I don't think so mate!

119

Out of the box thoughts on traditional mixes:

Old habits die hard –especially in Cape Town!

Julian Wise

DirectorZebra Bituminous Surfacing cc

But the traditionalists doggedlypersist in specifying it forlow-traffic roads and parking areas that:

• do not lend themselves toproduction paving or rapidcompaction;

• have a fair amount ofhandwork;

• have low quality base course(G3 to G5, laterite, crushedrubble, calcrete, all ofvariable quality), that is notfinished to a high standard;

• have actual asphalt;thicknesses that can easilyrange from 15 to 35mm.(Imagine the compactionwindow time for a 15mmthick area!).

The tradition joyfully continues bymaking sure that most of thesejobs are paved in winter, when aslong as it is not raining, it'sregarded as a good paving day!

"The job HAS to be handed overtomorrow y'know", followed by the phrase that has supported themovies for a generation “Don'tworry, everything will be OK".

Ja well no fine

And then the subtle assurance“I'm sure the Engineer willunderstand."

They don't say what it is theEngineer will understand – itusually turns out to be only whatthe specification says! And whenthe core results come out, they allpromptly forget about thepressure-cooker situation at thetime.

The result? Typical problemsencountered are:

• erratic and variable density,especially in winter;

• excessive permeability; • erratic surface finish,

particularly with handwork;• increased risk to the base

from the above.

The root cause of these problems? The mix design is not appropriatefor the application and 25mmthickness. (It is suitable forproduction paving of a 40mm thick layer.)

"Nonsense,” some of you will besaying, “I've been using this mixfor 35 years, and can show youmany roads that are still perfect."

Ja well no fine!

Granted, this mix is not acomplete disaster, but:

• specs have tightened – 95%Marshall has largely beenreplaced with 92% Rice;

• 60/70 pen bitumen hasreplaced the 80/100 used 35years ago;

• in my experience testing hasbecome “more thorough” toput it politely.

Certainly not every core will be afailure, but the more thoroughlyyou test this mix, the morefailures you generally find. I toocan name many roads and parking areas that have failed to someextent – failed in density andfailed to last a reasonable lifespan.Am I a lone wolf howling in thewilderness?

120

Or more appropriately, a lone thar bleating on the mountaintop?

Sabita's August 2006 edition ofAsphalt News has a short articleon research done by NCAT (USA)on Lift Thickness versus NominalMaximum Aggregate Size(t/NMAS). (NMAS = 1 size largerthan the first sieve to retain morethan 10%). This extensiveresearch can be found on thefollowing website:

www.eng.auburn.edu/centre/ncat/reports.

The report says it all in these“deep and meaningfuls":

• Mixes with larger maximumsize aggregates have largervoids that are more likely tobe inter-connected, resultingin higher permeability;

• As density decreases,permeability increases;

• As thickness decreases,permeability increases;

• Therefore mats that arethicker, with higherdensity and smallermaximum size aggregatewill be less permeable.

Figure 1 is a chart from thisresearch and shows the effect oft/NMAS on permeability. It is atrend curve for a variety offine-graded mixes, and NCAT'srecommendation is:

t/NMAS should be at least 3:1(Note the “at least")! Ourtraditional mix is 1.9:1, whichfrom Figure 1 indicates it may be60% more permeable than if itwas 3:1.

Oh dear, is our sacred cow indanger of becoming mincemeat?

121

Figure 1

The publication, Interim Guidelines for the Design of Hot Mix Asphaltin South Africa (prepared in 2001as part of the Hot Mix AsphaltDesign Project launched in 2001by SANRAL, the CSIR and Sabita), supports this. A few extracts are:

• Clause 2-16: Currentspecifications limit themaximum aggregate size tonot more than half thecompacted mat thickness.Designers should considerdecreasing this limit;whenever conditions areanticipated in whichcompactibility or segregationmight pose problems duringconstruction;

• Clause 2-18: Selection ofmaximum size aggregate i.e.9.5mm for 25mm thick mats;

• Clause 4-8: Minimum voids in the mix for light traffic is3.5%.

Impermeability

What should be the main purposeof such a thin layer on low qualitybase in a heavy winter rainfallarea?

Impermeability for a start!

Impermeability and goodcompaction go hand in hand. Wedon't want to pave thicker do we,that would be too much of a break in tradition. But we can easilydesign for higher density and lowpermeability.

Design the mix for quick, easycompaction – remember the veryshort compaction window time.

• Use a small maximum sizeaggregate;

• Use a high bitumen contentto provide good lubricationfor compaction;

• Target a low voids in the mix– light traffic will onlymarginally increase theconstruction density, so there is no risk of rutting orbleeding.

What were the origins of thisstubborn, ingrained tradition? BobKingdon tells a fascinating story.The construction of the freewaysystem in Cape Town in the 60'sprompted the establishment ofthree production HMA plants. Asfreeway projects tailed off, theproducers looked for alternativemarkets to keep their plants busy.

Cracked windscreens

In addition, the standard surfacing for residential roads then was asingle seal. To allow immediateopening to traffic, chips werespread at a rate 1.2 times higherthan was called for by the design.Result was a period of flying chipsand cracked windscreens until theteam came back to sweep up theexcess.

So the authorities were looking for an alternative, especially for thethen emerging Michells Plain. The wearing course for thefreeways had been approved andestablished – 40mm thick,13.2mm maximum size aggregateCCC mix.

So just reduce the thickness to20mm to make it economicalenough to compete with the single

122

seal, and everybody's happy! Orwere they? Bob remembers that this mix wasmade with 80/100-pen bitumen,and was paved on primedferricrete.

"It was not an unqualified failure,” he says ruefully, “but we hadendless problems with achievingdensity."

What's changed?

OK, so now it's a nominal 25mmthick, but is mixed with a stiffer60/70-pen bitumen that needsmore compactive effort to getdensity.

More rolling takes longer ... so the mat must stay hotter for longer –but it doesn't, does it!

Impermeability

Carl van der Merwe (UWP)designed a mix for Khayelitsharesidential roads about 10 yearsago. His main priority wasimpermeability to guard against:

• "grey” water damaging theasphalt and base;

• flooding due to blocked storm water catchpits.

The mix was basically a Colto Finepaved 25mm thick using:

• 6.7mm maximum aggregate;• 6% bitumen;• 1.5 to 3% voids in the mix.

"Oh horrors!” I hear some of youcry, “It will bleed, it will rut"...No it won't – the light traffic doesnot increase compaction over what

is achieved at construction. Goodcompaction was achieved evendoing handwork, and ten yearslater these roads are in reallyexcellent condition. It was a gooddesign and it worked.

Brian Roussouw (Kayad), thatsingularly innovative engineer,designed his township mixbecause he was sick of theproblems using the traditional mix. “I wanted a contractor-proof mixthat could be adequatelycompacted and looks good evenwith handwork,” he said.

Recommended mix

His “Kayad” mix is classed as a9.5mm NMAS fine-graded mix.Again this mix compacts moreeasily and is less permeable thanthe traditional.

If anyone is still reading anddoesn't consider this article thedemented ramblings of a biased,senile contractor, myrecommended specification toensure compactibility and lowpermeability for a 25mm thickmat, using Cape Town aggregates, is:

• a sound base with a highquality, primed finish;

• a tack coat;• a mix with 9.5mm max size

stone;• 3 to 4% target voids in the

mix;• bitumen content for this is

usually 5.5 to 5.6%;• filler/binder ratio 1.1 to 1.2.

The advantages are:

123

• Fewer roller passes needed to achieve compaction;

• Better and more consistentdensity;

• Improved permeability andthus more base protection;

• Less cold weather risk; • Better for handwork;• More durability and a longer

life.

The disadvantages are:

• Suitable only for light traffic;• It costs more (due to higher

bitumen content). OHHORRORS!

BUT IT WORKS. So decide foryourself whether you can afford itor not.

Now, let me get on to Cape Town's Colto Coarse wearing course,paved 40mm thick, but using amassive 26.5mm max size stone.When I bounced this mix designoff Bill Pine of Bailey Methodresearch fame, his reaction was“Ha, ha, ha, ha, ha. Good luck tothem!"

On second thoughts, maybe I'vebeen confrontational enough forone year, so I will save it for nextyear's Digest.

Acknowledgements

Julian Wise gratefully acknow-ledges the inputs of Bob Kingdon,Carl van der Merwe and BrianRoussouw. q

124

In 2002 Sabita undertookan evaluation study of theclassification and disposal

options for penetration gradebitumen in South Africa.

Samples of penetration gradebitumens from the four refineriesin South Africa, labelled, A to D,were analysed and evaluatedaccording to the Department ofWater Affairs and Forestry’s(DWAF) Minimum Requirementsfor the Handling, Classification and Disposal of Hazardous Waste, aspublished in 1998. The objectiveswere to classify the bitumens andto determine the type of landfillrequired for their disposal.

The approach in the MinimumRequirements is essentially a Tier1 or primary assessment of therisk posed by the materials to theenvironment, but the reportincludes an assessment of some of the Tier 2 or waste and sitespecific risks.

The analyses undertaken includeda head or total analysis of each of

the samples for organiccomponents by gas chroma-tographic and HPLC methods,together with leaching of thesamples using the ToxicityCharacteristic Leaching Procedure(TCLP) of the US EnvironmentalProtection Agency (EPA). Theleach solutions were analysed fora wide range of inorganic andorganic analytes.

Classification

The Minimum Requirementsdemand a primary classification ofthe cold bitumen according toSABS Code 0228; the foursamples were non flammable, i.e.the flash point is 610C; corrosive,i.e. the pH is >6 or <12 orreactive. Therefore, the onlypossible hazardous characteristicis that of toxicity, which for a solid material is determined bycomparing the concentrations ofany inorganic or organiccomponents leached, with theguideline limits, i.e. the acceptable risk limits for any leachedconstituents.

126

The status quo on landfill sites:

Disposal of penetration gradebitumen in South Africa

Dr Mannie Levin

GeohydrologistAfricon Engineering International (Pty) Ltd

The total analysis of the bitumensshowed that they contained smallamounts of volatile aromatichydrocarbons, notably the BETXcompounds and trimethylbenzeneisomers, plus low amounts ofpolycyclic aromatic hydrocarbons(PAHs) such as naphthalene,anthracene, phenanthrene andpyrene: none of the PAHsobserved are classified as knownhuman or animal carcinogens.

Traces of chloroform, bromo-dichloromethane and phthalateesters were also detected in someof the samples. Although theseorganic species were identified inthe bitumen samples, only toluene was detected in the leach solutions – but at trace levels close to thedetection limit of 1ppb. There are,therefore, noorganic compoundsleached from thesamples that canhave a significantimpact on theenvironment.

Two samples of thepenetration gradebitumen, B and D,leached Pb atconcentrations justabove its acceptable risk limit of 0.10mg/l and, thereforeformally classify ashigh hazard (HG2) wastes in terms of the Minimum Requirements.Samples A and C formallyclassified as non-hazardous interms of the MinimumRequirements. Even though awaste formally classifies ashazardous it can be delisted fordisposal to a general waste landfill

provided the estimatedenvironmental concentration isless that the acceptable risk limitof the species, in this case Pb.

Therefore, all the penetrationgrade bitumens delisted fordisposal to general waste sites and can be disposed to medium orlarge general waste landfills thathave a leachate managementsystem, i.e. GMB+ or GLB+.

Final report

The final report produced early in2003 proposed that application bemade to DWAF for approval of thedelisting of penetration gradebitumens and that this include arequest also for disposal to GB-sites because GB+ landfills are not

available in manyareas within areasonabletransport distance.

In their replyreceived on the 9thJune 2004 DWAFgave permission forbitumen waste tobe considereddelisted subject tothe conditions thatif any uncertaintyexists aboutwhether a specificmaterial falls within

the tested parameters, thenfurther analysis and leachate tests may be required. The delistedmaterial may only be disposed ofon a permitted facility, after thePermit Holder has applied andreceived written permission fromDWAF.

127

There are no

organic

compounds

leached from

the samples

that can have

a significant

impact on the

environment.

In August 2004 a status quoreport was produced on theavailable landfill sites that could be considered for the disposal ofpenetration grade bitumen. Aregister of available sites wasobtained from DWAF, and it wasconcluded that a limited number of B+ sites exist in South Africa andB- sites will have to be considered.

Sabita members were asked toindicate their choice for localitieswhere sites should be available,and to provide an estimate of thedisposal volume. Twenty five siteswere selected, and letters weresent to these sites informing them of the delisting, and of the request from Sabita that they be permitted to receive delisted penetrationgrade bitumen.

Poor response

The response was poor, with onlya few sites reacting to the request. Margate indicated that theestimated amount of bitumenwaste at that site did not warrantthe cost of permitting. EastLondon indicated that their Second Creek site was closing down andwas not available. Similarly, theGeorge site closed down andcannot be considered. The goodnews was that Durban wasconsidering permitting some sitesand that Ekurhuleni MetropolitanMunicipality permitted theirRietfontein Landfill Site.

The new Environmental Act cameinto effect on 1 March 2006 andthe responsibility for permittinglandfill sites was transferred fromDWAF to the Department ofEnvironmental Affairs and Tourism

(DEAT). Communication withDWAF and DEAT during this period did not produce any results onapplications for permitting by anyof the selected sites. A new letterwas sent to the selected sites, now reduced to eighteen, informingthem of the change andrequesting them to submit new orresubmit applications (if submitted previously) to DEAT in Pretoria.

The result was disappointing, assome letters were returnedunopened because municipal sitesclosed and district municipalitieshad taken over and opened newsites. The register at DWAF wasclearly outdated. A new effort wastaken and each municipality andor district municipality contactedto find the authority andresponsible person with whom tocommunicate.

The sites were now reduced to just 11, excluding any municipal orcommercial H:H sites. Most people are positive regarding permitting,subject to fund availability and/ora final acceptance of the requestby the Local Council.

It is uncertain how long it will take before adequate facilities fordisposal of penetration gradebitumen are available. IMIESA inits October issue published anitem informing people of Sabita'sefforts to promote all aspects ofhealth, safety and environmentalconservation in the South Africanbituminous products industry. Theefforts of Sabita will howevercontinue, and with the support ofDWAF, DEAT and the localauthorities, permitting should befinalised during the next year. q

128

Worldwide, the designand construction oflong lasting asphalt

pavements is becomingincreasingly important asgreater demands are placed on the performance of theseasphalt layers.

Adequate bonding betweenasphalt layers is critical if thecompleted structure is to behaveas a single structural unit andprovide adequate strength. If thelayers are not properly bondedtogether, they will behave asindependent thin layers.Generally, such individual layersare not designed to accommodatethe stresses imposed by currenttraffic patterns. Damage due tofatigue and deformation proceedsat a faster rate when a properbond has not been created,resulting in rapid deterioration ofthe pavement structure.

Inadequate bonding can result indelamination, cracking, potholesand ingress of water into thepavement structure.

Over-application of the tack coatcan result in slippage of theasphalt layers due to thelubricating effect of the excessbinder.

Tack coats

Tack coats have traditionally beenused in South Africa for improvingthe adhesion of hot mix asphaltlayers to the substrates on whichthey are placed. These mixes areusually placed at a thickness of 15 – 60mm. Anionic stable mixemulsion diluted with equalquantities of water is commonlyused for this purpose. Theapplication rate specified in COLTO is 0,55 l/m2 for a 30% bindercontent emulsion, leaving a netresidual binder application ofapproximately 0,165 l/m2. Themethod of application is often with a hand sprayer, and the resultingspread rate and evenness ofapplication usually leaves much tobe desired and may be referred toas “a lick and promise”. Pavingcan only commence after theemulsion has “broken”.

130

Adequate layer bonding critical:

Bond and tack coats to improvetotal structural integrity

Kobus Louw

Research and Development ManagerColas SA (Pty) Ltd

Bond coats

Bond coats were first used withthe introduction of the integratedpaver/sprayers for application ofUltra Thin Friction Course (UTFC)asphalt in South Africa in 1999.These thin, open graded asphaltlayers are placed at an averagethickness of 18mm. The strainsinduced by traffic at the surface/binder interface are much greaterthan the forces acting on thethicker asphalt layer/binderinterfaces, and undiluted rapidsetting cationic polymer modifiedemulsions are thus used for thispurpose to ensure adequate bondstrength at the interface.

The thin asphaltsurfacing layer andthe bond coats areusually offered asan integral packageby the applicators.The paving unitapplies the binderuniformly using acalibrated,computercontrolled, spraying system. In the case of simultaneous application, thefree water in the emulsion bondcoat foams when it comes intocontact with the hot mix asphalt.The reduced viscosity of thefoamed binder and its subsequentexpansion allows the binder topenetrate more effectively into the existing substrate and overlyingmix, thus creating an improvedbond.

Application rate of the bond coatvaries typically between 0,4 – 0,6l/m2 depending mainly on the

substrate texture, leaving aresidual modified binderapplication of 0,26 to 0,39 l/m2,which is considerably higher thanthe residual binder content usedfor the conventional, thickerasphalt lifts. The thicker residualbinder layers also provide betterwaterproofing, as the thinner,open graded asphalt layers aremore prone to allowing waterinfiltration compared to theconventional, dense layers.

Specific requirements

• High softening point ofresidual binder to preventexcessive migration into the

open UTFCaggregatestructure undertraffic afterpaving;

• Very rapidsettingcharacteristics.The UTFC layer is very thin andrapidly coolsdown afterpaving. Duringthe time interval

when the mat is at atemperature in excess of1000C, most of the water inthe emulsion should boil off.The emulsion should besufficiently de-stabilisedduring this short period toprevent re-emulsification,which could occur ifunexpected rain falls on thesurface within the first fewminutes after paving;

• Despite the rapid settingcharacteristics required of abond coat, the emulsion

131

Deformation

proceeds

at a faster

rate when

a proper bond

has not been

created

should also be stable enoughto withstand repeated heating cycles during handling andthe highly detrimentalshearing action of thetransfer and dosing pump onthe paver.

Benefits associated with the use of bond coats are:

• Greater cohesive strengths;• Greater adhesion;• Improved waterproofing.

Modified emulsions

SBR modified bitumen emulsions(three phase emulsions) arecommonly used worldwide as bond coats. In Europe and America, SBS modified bitumen emulsions (twophase emulsions) are growing inpopularity for this type ofapplication. These emulsions arenot yet available in South Africa,due to the specialised equipment

required in the manufacturingprocess.

Evaluation

(i) In Britain, bond coats arecharacterised in the Specificationfor Highway Works (SHW) by their Vialit Pendulum Peak BinderCohesion value. The test involvesthe measurement of the cohesionof recovered emulsion bindersover a range of temperatures toobtain a cohesion-vs-temperaturerelationship. A stainless steel cube with a surface area of exactly 1 cm2 is attached, using a 1mmthick film of the recovered binder,to another fixed cube of similararea. The energy required todislodge the cube at varioustemperatures by a swingingpendulum arm is determined.Intermediate grades should have a minimum peak value of 1,0J/cm2 while the high performancegrades should have a minimum

132

Figure 1

peak value of 1,2 J/cm2. Typicalresults appear in Figure 1.

(ii) Julian Wise and DerickPretorius conducted tests in 2003to determine the shear forcerequired to dislodge a UTFC layerfrom a continuously graded SABSmix.

In summary the followingprocedures were conducted:

• Base briquettes wereprepared in Marshall mouldsaccording to the SABS mixspecification, and compactedto 88% and 90% respectively of Rice, and allowed to cool;

• Bond coat applied on top ofSABS mix, followed by UTFC,and compacted with 100blows on one side only;

• Composite briquette pushedpartly out of mould to expose joint;

• Load applied with a CBRpress to determine shearforce.

The effect of the bond coatapplication rate on thepermeability of the SABS mix wasalso evaluated. The results aresummarised in Table 1.

Handling

Unlike conventional tack coatemulsions, bond coat emulsionsare very shear and temperaturesensitive, and should be handledstrictly in accordance to themethod prescribed by thesuppliers. These are generallylatex modified emulsions, whichare sensitive to pumping andheating. Excessive pumpingand/or heating forms tough,irreversible deposits, which canblock the very small nozzles usedby the integrated paver/sprayers.This can often lead to extensivedelays on site. Special care should thus be taken during loading,heating and transfer operations toprevent damage to the emulsion.

Bond strength

The bond between the overlaidmaterial and the existing surfaceis a function of:

• Application rate: the quantityof tack or bond coat requiredis a function of the surfacetexture of the overlaidsurface. Rough, milledsurfaces have a surface areaapproximately 30% larger

133

Bond coat (l/m2) Degree ofcompaction (% of Rice)

AveragePermeability

l/hr

AverageTangential

Tension (kPa)

0.4 88 1.3 853

0.4 90 0.2 689

0.7 88 2.6 831

0.7 90 0.2 772

1.01 88 0.4 882

1.01 90 0 752

Table 1

than smoother surfaces, andthe quantity of tack or bondcoat required for optimumadhesion is thus also larger.Under application can lead tobond failure, whileover-application can lead toslippage and bleeding in thecase of UTFC. The migrationof excess binder from thebond coat into the UTFC isthe single greatest risk to the functional performance of the new layer. For example anover application of 0.1 l/m2 of net binder which migratesinto the UTFC can increasethe binder content of a 4.5%binder contentUTFC mix by0.35% andreduce the airvoids by 3%!;

• Surfacetexture:roughersurfaces willadhere betterto the overlaidasphalt layerthan smootherlayers;

• Type of binder: very thinlayers generally requireundiluted polymer modifiedemulsions for optimumadhesion due to the largerstresses to which thesesurfaces are subjected;

• Uniformity of application ofthe tack/bond coat: wherepossible, these materialsshould be applied with acalibrated binder distributoror spraying system to ensurea uniform and accurateapplication rate. At least 90%

of the surface should beevenly covered to preventdefects in the overlaidmaterial;

• Cleanliness of the existingsurface – tack or bond coatswill not adhere to dusty, dirty surfaces and will be picked up by site traffic, leaving areaswith insufficient binder toensure proper adhesion ofthe overlaid material;

• Control of site traffic: sitetraffic should not be allowedonto tacked areas before theemulsion has broken. Theunbroken emulsion will bepicked up on the vehicle

tyres, leavingareas withinsufficientbinder to ensureoptimumadhesion.

Properties

Mostly, anionicstable gradeemulsionsconforming to therequirements ofSANS 309 are diluted and used as

tack coat emulsions during hotmix applications. In someinstances cationic spray gradeemulsions, conforming to SANS548, are also used in a dilutedform. However most users areunaware of the fact that cationicspray grade emulsions almostalways contain a certainpercentage of hydrocarbon solvent (flux). As this type of emulsion isgenerally used for surface dressing operations, the hydrocarbon flux is added to soften the binder and

134

An over

application of

0.1 l/m2 of net

binder which

migrates into

the UTFC can

reduce the air

voids by 3%

promote the breaking of theemulsion. It also enhances earlymosaic development of the stonematrix in a seal.

The quantity of flux in cationicspray grade is varied on aseasonal basis, with the higherhydrocarbon levels being usedduring winter months. SABS 548specifies a maximum allowableflux level of 5% m/m of residualbinder. Should cationic spraygrade emulsion be used as a tackcoat, the flux component will betrapped under the overlaidmaterial. Although generally not aproblem in most pavingapplications, the use of cationicspray grade emulsions should beavoided on high stress areas, dueto possible problems with slippageor creeping of the asphalt layer.Anionic stable grade emulsionscontain no hydrocarbon solventsand are thus preferable for tackcoat applications.

Typical properties

No national specifications exist forbond coat emulsions. Theseemulsions are supplied by themanufacturers, who provide theirown specifications. Typicalproperties used to classify a bondcoat emulsion are: binder content, viscosity and residue on sievevalues. Minimum softening pointand elastic recovery values arespecified on the residual binderafter evaporation of the waterphase. These properties shouldcomply with the requirements ofTG1’s SC-E1 grade modifiedemulsion for seals, except that the product must not contain any

hydrocarbon fluxes. It is possiblethat the specifications for theseemulsions will be included in therevised TG1 guideline to bepublished later this year.

European developments

A common problem associatedwith the use of tack coats is “pickup” of the broken emulsionresidue under the wheels of thetipper trucks supplying the hot mix asphalt to the pavers. Thiseffectively results in areas wherelittle or no binder remains on thesurface, which can result inslippage cracking or delaminationof the asphalt layer.

A new type of tack coat emulsion,such as the Colnet systemregistered in the name of Colas SA in France, has been developed inEurope, and is known as “cleanemulsion”. Essentially a hardgrade of bitumen is emulsifiedusing specialised equipment, andthe emulsion is applied with aspecially adapted binderdistributor using three spray bars.

The first spray bar applies anadhesion agent to the existingsurface, while the second, or main bar, applies the emulsion. Thethird spray bar applies a chemical“breaking agent” on the emulsionto destabilise the emulsion andinduce chemical breaking. Pavingcan commence immediately afterapplication of the emulsion and“pick-up” on the truck tyres doesnot occur (see Figure 2). Thissystem allows paving work toproceed at night, with no delaysbeing caused by slow breaking ofthe tack coat.

135

"Clean"emulsions

During the developmental stage of the Colnet system, Colas in France performed comparative tests inthe laboratory with conventionaland “clean” emulsions to evaluatethe development of the bondstrength over time. The emulsionwas applied in an even layer onaluminium trays and small glasscylinders were positioned on theemulsion layer. In the case of the“clean” emulsion, the breakingagent wasfirst evenlysprayed overthe emulsionlayer beforepositioningthe glasscylinders. The strainrequired todebond thecylinders was thendeterminedover time(See Figure3).

Conclusion

Tack coats and bondcoats are critical to thesuccessful performanceof hot mix asphaltsurfacings. Although the design and constructionof hot mix asphalt layers always receive detailedattention, the selectionand application of tackand bond coats often do not receive the attention they deserve despite

their influence on the overallperformance of the new pavedsurface. Hand application of tackcoat is still common practice inSouth Africa, but is forbidden inmost developed countries. Shouldthe use of calibrated bindersdistributors eventually becomecompulsory for the application oftack coats, the emulsion producers will have greater incentives toproduce innovative binders for this market sector. q

136

Figure 3: Bond strength – Conventional vs “clean"emulsion

Figure 2: “Pick-up” on truck tyres

As part of its undertakingto develop a performance classification system for

South African bitumen, thespecific working group of theRoad Pavements Forum (RPF)task group on binderspecifications, has arrangedfor bitumen from all four localrefineries to be tested forcompliance with the SHRPSuperPave grading system.

This testing was arranged byProfessor Kim Jenkins, convenor of the working group, to beconducted at the UniversityWisconsin, Madison by membersof the research group headed byProfessor Hussain Bahia.

In Nov 2003 the RPF Resolved that ” the Bitumen SpecificationsWorking Group be reconvenedwith the objective of reviewing the South African binder specifications relative to international trends ofPerformance Grading (PG). Aprecursor of the above reviewprocess was the fingerprinting ofvarious South African crude source binders using the American PG

System. Professor Bahia played akey role in the development andimplementation of the SHRPbinder grading system and, having had several years of involvementin South African binders, kindlyagreed to assist in both the testing and the interpretation of the PGresults.

Fingerprinting

In general, the test resultsconfirmed that the bitumen,sampled from all four SouthAfrican refineries for thefingerprinting, complies withspecific grades of the SuperPaveclassification system. This isencouraging, and will lay a soundplatform for developingperformance related specificationsin SA. The full range of lowtemperature tests were notconducted on the binders (e.g. the Direct Tension Test (DTT) wasomitted) as these are not directlyapplicable to the in-serviceconditions encountered in the SAclimate. However, some additional

138

Bitumen stabilised materials:

A performance classificationsystem for SA ... Quo Vadis?

Kim Jenkins

ProfessorSANRAL Chair

University of Stellenbosch

testing was incorporated in theproject and is reported on.

Strategy

Fingerprint testing carried out atMadison covered the following:

• Standard Dynamic ShearRheometer (DSR) testing on:

º Unaged binder (withrepeats);

º RTFOT aged;

º Pressure Ageing Vessel(PAV) aged.

• Additional DSR testing on two manufacturers of apparatuses at:

º 0.1% strain versus 12%strain;

º Different times of day(temperature control).

• Bending Beam Rheometer(BBR).

Standard DSR testing at 12%strain (ε), according to SHRPprotocols, was carried out. Inaddition, the Shear Modulus G*versus Frequency was measuredat 0.5% ε for bitumen from fourSA refineries, as shown in Figure2.

The DSR results show particularlygood agreement between themeasurements at different strainlevels, verifying that the 12% ε iswithin the linear range of testing.This verifies that SHRP’s reasoning for adopting 12% ε as theirstandard protocol is sound andapplicable to SA bitumen too.

The SHRP SuperPave GradingSystem classifies a binder bydefining the average 7-daymaximum pavement designtemperature (ºC) as well as theminimum pavement design

139

Figure 1. Figure 1. Bitumen grades sampled from 4 refineries for finger printing

temperature (ºC) that the bindercan reliably withstand.

For example, PG 64 – 22 would be appropriate for use in asphalt inan area with an average 7-daymaximum temperature of 64ºCand a minimum temperature of-22ºC. Based on the testingcarried out at Madison apreliminary SHRP classification of

the SA binders from the fourrefineries tested yielded thefollowing:

While a cursory glance at theclassification may indicate thateight grades are required for SAbinders, the SA climate and theneeds of the SA roads industryhave not yet been considered. It is conceivable, for example, that thenumber of grades could be

140

Bitumen grade 40/50 60/70 80/100 150-200

SHRP SuperPaveClassification:Refinery A to D

X PG64-16 PG58-22 X

PG64-16 PG58-22 PG58-22 X

PG64-16 PG64-22 PG58-16 PG52-22

PG70-22 PG64-22 PG58-22 PG52-28

Table 1: SA binder classification from fingerprinting July 2005 bitumen samples

Figure 2: DSR testing at comparative strain levels

reduced to, for example, four, if asingle lower temperature isadopted. These issues, along withthe temperature intervals of theclassification system, will bedebated by the RPF BinderWorking Group.

Temperature zones

It is indeed encouraging to notethat SA bitumen meets thestandards adopted in the USA,especially the good lowtemperature classification;however, there is still some workto be done, including identifyingappropriate temperature zones inSA and appropriate binder tests,especially the simulation of longterm ageing. For this purpose,alternatives to the PAV such as the Belgian Rotating Cylinder AgeingTest (RCAT) and possibly aprolonged RTFOT, are underinvestigation.

In addition, the differentrequirements of surface sealsversus asphalt surfacing, need tobe taken into account. Theselection of critical binder test

parameters and the identificationof appropriate limits to reliablyinterpret susceptibility to, forexample, permanent deformationor cracking, will also need beinvestigated. Zero Shear Viscosityhas been recognisedinternationally as a criticalproperty that could assist inidentifying permanentdeformation, and will need to beconsidered.

Acknowledgements

The refineries are commended forsupporting this study, as well asProf. Bahia and his team forcarrying out the testing at such areasonable cost and for providingtechnical insights. We now have asnapshot of really usefulrheological information to guide us with possible bitumen gradings. Itdoes not stop here, however;research on applicable long-termageing simulation tests andexperimental (non-conventional)tests on the binders, will continuein the quest of a suitable systemfor South Africa. q

141

The publication in 2001 ofthe Asphalt Academy’s(AsAc) TG 1 – Technical

Guidelines: The use ofmodified binders in roadconstruction, was a major step forward in providing a singlegeneric industry guidelinecovering the use of modifiedbinders in South Africa.

The introduction of generic binderclasses, which are “polymer blind”but required to conform to endproduct property limits appropriate to the specific application, wereviewed by many practitioners atthe time as being fairly “radical”.However, over time these genericclasses have steadily gainedacceptance to a point wherespecifiers, producers and usersnow generally feel entirelycomfortable with the system.

Review

Over and above normal goodpractice of reviewing technicalguidelines approximately everyfive years, the field of bitumen

modification is internationally avery dynamic one. As a result, atthe November 2005 meeting ofthe Road Pavements Forum aresolution was passed toreconvene the task group toreview the 2001 edition of TG 1.

This reconvened group consists ofmany who where members of theoriginal task group, withrepresentation from roadauthorities, researchers,consulting engineers andcontractors, as well as bothprimary and secondary binderproducers. AsAc is fulfilling therole of secretariat. The initial phase of the projectconsisted of critically reviewing the following issues:

• Applicability of current binder classes;

• Guidelines with respect toselection criteria;

• Appropriateness of currenttest protocols;

• Appropriateness of currenttest limits;

143

Revision of Technical Guideline 1 (TG 1):

The use of modified binders inroad construction in SA

Dennis Rossmann

Materials and Pavement EngineerSANRAL, Eastern Region

• International specifications/trends etc. and theirappropriateness for SouthAfrica.

From this initial process it becameevident that the revision processcould not just be confined to alimited updating exercise. Overand above identifying some of theexisting criteria that requiredamendment, major additions tothe document were required toprovide additional guidance topractitioners, especially the newerentrants into the industry.

Amendments

Some of the more significantproposed changes to the existingdocument are detailed below:

• Applicability of currentclasses: Even with the benefit of hindsight, the originaldecision to limit the numberof modified binder classeswas a good one. With theacceptance that the binder isbut one component of thefinal product, the currenttrend internationally is toreduce the existing numberof classes to a moremanageable and pragmaticone. Notwithstanding theabove however, it has to beaccepted that, whileelastomers (SBR, SBS & B-R) are still the most commonlyused modifiers, otherproducts such as plastomers(EVA), natural hydrocarbonsand Fischer-Tropsch (FT)waxes are currently beingmore widely utilised. As such, the present binder

classification matrix will beexpanded where possible toinclude these products;

• Specialised applications: With the increased use of modified binders in a variety of roadapplications, the guidelineswill be expanded toincorporate these specialisedbinders, such as modifiedemulsions used inmicrosurfacing and bondcoats for UTFC’s, and highmodulus and fuel resistantbinders used in hot mixasphalt;

• Appropriateness of currenttest protocols: While theexisting test protocols andassociated property limits are not fundamentallyperformance based, theyhave been derived frompractical experience gainedover some considerable time. It is envisaged that, whilesome of the current testsclassified as “Report Only”will be removed, the testregime for the differentclasses will be consolidated.This is to ensure that we usethe most appropriatemeasures, in which thebinder is expected to perform in-service and duringhandling, to control thebinder’s performance;

• Appropriateness of currentproduct property limits: Anumber of amendments tothe existing product propertyrequirements have beenidentified, some of which are:

º “tightening up” theallowable limits on someproperties;

144

º introducing upper limits on some properties, such asSoftening Point ranges;

º bringing some of the limits more in line withachievable productionexperience.

• Selection criteria: Thissection is being significantlyexpanded to give moreguidance with respect toselecting the mostappropriate modified binderclass for a given expecteddemand. Aspects such asassociated construction,environmental and production constraints relative to aspecific binder class will alsobe included;

• Associated issues: aspectssuch as quality managementduring storage and handling,as well as HSE issues, are to

be expanded to a greaterdegree. This is to ensure that the finished product, once itleaves the blending plant, ishandled in a safe andappropriate manner and thatit remains within thespecification.

Conclusion

It is envisaged that the revised TG 1 document will be a significant improvement on the 2001 edition.With the ultimate goal offacilitating the specification of pure performance-based requirementsstill on the horizon (albeit evercloser), it is hoped that thedocument will reflect current bestpractice in South Africa and thusensure optimal utilisation of theseproducts. It is currently planned to release the second revision in thefirst half of 2007. q

145

Schematic of the three-dimensional SBS network. (Courtesy of Shell Bitumen)

The basic philosophy forthe design of stone sealsin South Africa was

developed by F.M. Hansen inNew Zealand during the mid1930s. The principle appliedwas to partially fill theavailable voids aroundaggregate particles to retainthe stone on the road undertraffic and expected climatic

conditions.

Road authorities in South Africaapplied and adjusted thisphilosophy to suite their particularconditions to great success, themajority specifying the applicationrate for a given situation, basedmainly on traffic and aggregate

size.

Initial efforts by the formerCommittee of State RoadAuthorities (CSRA) and the CSIRto develop a single designprocedure for South Africanconditions were not successful,resulting in guideline documentsincorporating a compendium of

design methods.

During the early 1980s polymermodified binders were introducedto South Africa, adding to the

complexities of design.

Although not without difficulties,the Committee of Local TransportOfficials (COLTO) succeeded, to alarge extent, in unifying thevarious design approaches andalso in incorporating designguidelines for modified binders inthe Technical Recommendationsfor Highways (TRH3, Draft 1998).

By accepting that each roadauthority’s design provides anacceptable seal, the “RationalDesign” approach, as developedby the CSIR and the Departmentof Transport, was adjusted toobtain a range of appropriate

binder application rates.

The adjusted “Rational Design”determines the minimum volumeof binder to retain aggregate andthe maximum volume to providesufficient macro texture for skidresistance, taking into account the

147

Revised TRH3 imminent:

Developments in seal design

Gerrie van Zyl

DirectorPD Naidoo & Associates (Pty) Ltd

void loss due to embedment and

aggregate wear due to traffic.

Stone loss

Feedback from practitionersindicated satisfaction with theguidelines provided forconventional bituminous binders.However, guidelines for the design of seals with modified binderswere questioned, as stone lossoften occurred on single seals andbleeding could be expected ondouble seals.

The South African National RoadsAgency Ltd (SANRAL) took theinitiative to update and to improve the TRH3 (1998). The 2007version is expected to be available on both the SANRAL and NDoTwebsites by March 2007.

The document,already reviewedby experiencedpractitioners,includes revised ornew guidelines and

practical hints e.g.:

• Design ofboth singleand double

seals usingmodifiedbinders: Thedesign method is now based onthe conventional binder designwith provision of one adjustmentfactor to caterfor specificmodified binders and traffic

situations. Tables areprovided to select appropriate

adjustment factors;• Design of split application

double seals: The use of the19/6,7 split applicationdouble seal (19,0 mm andtwo layers of 6,7 mmaggregate) has increaseddramatically on high volumeroads in South Africa. Thisseal is designed andconstructed to createadditional voids for themovement of the bituminous

binder and has the ability to:

º Accommodate reasonablysoft existing surfaces as a

result of bleeding;

º Reduce rutting;

º Reduce water spray behind

large trucks.

148

• Selection of appropriatebinders to suite prevailingconditions: Specific attentionis given to emulsions and

rejuvenators;• Graded aggregate seals:

Guidelines from experience in Botswana has been

incorporated;• Geotextile seals: Provisional

guidelines are based onexperiences in South Africa,

Namibia and Australia;• Precoated sand seals:

Although considered to be the cheapest seal, excellentperformance has beenreported, even on relatively

high volume roads;• Labour intensive seals:

Additional guidelines onslurry-bound Macadam seals

are provided;• Slurry seals: Additional

information and referencesfor design purposes are

provided;

• Practical minimum andmaximum binder applicationrates: The theoreticallymodelled design curves havebeen adjusted to preventunnecessarily high binderapplication rates or rates

below the practical minimum;

• Pre-design tests andinterpretation of test results:Specific emphasis is placedon the “ball penetration” and

“sand patch tests”; and

• Reference is made to thelatest companion documents

e.g. Sabita manuals.

Several courses are planned for2007 by the Asphalt Academy(AsAc) to introduce the latestrecommendations on seal design

and application. q

149

S-E1 AdjustmentConventional to Modified Binder

Traffic ELV Single Seal Double Seal Split application double seal

< 5000 1.3 1.0 1.1

5000 – 20 000 1.2 1.0 1.0

> 20 000 1.1 1.0 1.0

At the Conference onAsphalt Pavements forSouthern Africa (CAPSA)

2004, the decision was made,in line with global bestpractice, to discourage the useof coal tar products in roadconstruction in South Africa.

This decision resulted in SasolCarboTar closing its operations inJune 2006, which drasticallyreduced the availability of coal tarproducts in the market and leftonly one source of coal tarproducts, namely that from MittalSteel. The result was a significantreduction in the range of primeproducts available for the roadconstruction industry.

In the second half of 2006, Sabitalaunched a series of seminarsunder the auspices of the Societyfor Asphalt Technology (SAT) inthe Gauteng, KwaZulu Natal andWestern Cape regions to promotethe discontinuation of coal tarusage. The seminars were wellattended and suppliers were given the opportunity to promote

alternative products andtechniques to coal tar for priminggranular bases and precoatingsurfacing stone.

Contractor problems

Contractors complained that tarproducts such as RTL 1/4P, RTH1/4P and Sasol Quick Dryingprimes wetted and cured quickerin practice than cutback bitumenprimes such as MC 30.

Table 1 compares properties of the different materials.

In general, it has been found thatinvert bitumen primes work betterthan cutback bitumen primes.

Yet, despite the properties of theprimes, other factors such as thedensity and type of base material,also create havoc for thecontractor. The moisture contentand temperature begin affectingthe performance of the prime inthe application, and the end result is an undesirable primed surfacewhich causes delays in

150

Alternatives to coal tar products:

The influence of weather onprime applications

Johan Muller

Assistant Technical ManagerTosas (Pty) Ltd

construction. Placing hot mixasphalt or a seal on a prime thathas not penetrated into the basesubstrate raises the probability ofproblems appearing later duringthe life of the surfacing.

Penetration

The penetration and dryingproblems with primes are worse in winter and this led the technicalteam at Tosas to investigatevarious ways to overcome theseproblems. The fact that theviscosity of bituminous productsincreases at lower temperaturesprompted the Tosas team toinvestigate ways of decreasingviscosity. The alternatives were:

• Increase the percentage ofcutter to reduce the viscosity: This is standard practice andall suppliers can make thealterations, formulating anon-SABS 308 product,(unfortunately at a cost tothe client). For example: MC30 + 10% additional paraffin;

• Change the solvent type:(This was also investigatedand may prove to be alonger-term solution if thespecifications for cutbackproducts are amended);

• Emulsify the cutback bitumen in water: i.e. normal

‘oil-in-water’ as opposed toinvert emulsion where thewater is the discontinuousphase. (Although theviscosity is reduced, one canbe fooled by false penetration – although the water andsome of the solventpenetrate, the bitumendroplets are unable to do so,and coagulate on top to forma skin. A high concentrationof soap is also required toemulsify the product, whichhas a water content ofbetween 40 and 50%. Thislarge proportion of free water reduces the net bindercontent dramatically, and the contractor would be better off spraying bitumen primes at30-40% below specifiedapplication for the sameeffect.);

• Look at the effect oftemperature.

Temperature

Everyone knows that it is colder in winter and warmer in summer, airtemperatures are lower than theroad temperatures as it is warmerin the direct sun than in theshade.

The clever philosopher who oncesaid: “You do not know that which

151

Properties Tar Prime Cutback bitumenprime

Invert bitumenemulsion

Water content 0% 0% < 20%

Solvent type Polar Non-polar Non-polar

Solvent Creosote-like Paraffin-like Paraffin-like

Viscosity Low Highest Lower thancutback bitumen

Table 1: Tar vs bitumen primes

you don’t measure” might havebeen looking over our shoulders,because we did not know how toquantify the effect of temperature, and an interesting exercise started as a result of various otherresearch initiatives.

Binder suppliers and appliers, aswell as contractors, are normallyat the mercy of the elements. If itis not too cold it is too wet, if it isnot too wet it is too dry. By justusing some proper engineeringjudgement, however, we can solve and prevent many problems wecreate for ourselves by notmeasuring temperature. Wemeasure density and moisture and binder application, but we do notpay enough attention to road andair temperatures when priming isdone.

Geography

The Gauteng Highveld is dry forthe majority of the winter. Theabsence of rain makes winter anexcellent time to do roadconstruction, but overnighttemperatures are sometimes verylow and may cause problems,especially in seal and primeapplications.

We investigated the following:

• Temperature variationsduring the course of a day;

• Differences between air androad temperatures;

• The effect of sun and shadeon these temperatures;

• Variation of these conditionsfrom season to season.

By knowing the answer to thesefactors we believed it would bepossible to make the followingjudgements:

• Will it be possible to prime;• At what time can the

contractor start the primingoperation;

• At what time should thecontractor stop the primingoperation;

• What will the effect of shade(or cloud cover) be onpriming operations.

Although this knowledge cannotguarantee success, it can surelyminimise problems andunnecessary losses of time andmoney.The following assumptionswere made:

• Spring and autumn will beconsidered sensitivetransition periods;

• A gradual warm-up will occurin spring, and the reverse inautumn;

• Winter is the most criticalperiod;

• Summer is generally not aproblem in terms oftemperatures but wind, cloud cover and rain can affect thetemperatures.

Observations

Daily temperature variation

It is interesting to note that theincrease in temperature followsthe same trend but temperaturesvary significantly between air,road, sun and shade – see Figure 1.

152

August 2006, as monitored in thegraph above, was cold and is stillconsidered as winter in Gauteng.

Although the road temperaturewas still increasing at 15h00 in the sun, the road temperature in theshade started to decrease at14h00 with the decrease in the air temperature. The road tempera-

ture differences were also thelargest between sunny conditionsand shady conditions.

Air-road temperatures

The road temperatures in theshade changed very little duringthe day and, depending on theovernight temperature, it

153

Figure 1: Daytime temperature profile for 11 August 2006

Figure 2: Daytime temperature profile on 1 December 2006

gradually increased fromapproximately 100C in winter tomore than 250C in summer. Whenit was windy and cloudy, the airand road temperature in the sundropped to the shade tempera-tures.

Sun-shade temperatures

The minimum-maximum rangesfor the air and road temperaturesin the shade were of the samemagnitude, yet the airtemperature was always higherthan the road temperature in theshade in the morning. The roadtemperature gradually increasedduring the day and the airtemperature usually peakedbetween 13h00 and 14h00,decreasing thereafter. The latterwas true for the air temperature in the sun, but the road temperaturein the sun peaked much higherand also earlier (around 12h00).

The road temperature alsodropped significantly faster incomparison with the airtemperature, which was directlyrelated to the amount of directenergy from the sun.

The season, wind, cloud cover and time of the day all play asignificant role on both the air and road temperatures.

Shaded areas are affected morethan sunny areas. Care should betaken when wind and rain arepresent. Then, even in the sunnyareas, temperatures drop at analarming rate.

Wind, cloud and rain

When the conditions becomecloudier, the road temperature isaffected more rapidly than the airtemperature. When the cloudcover disappears, the roadtemperature also increases more

154

Figure 3: Average temperature variation during October 2006

quickly. The effects of sun andshade on temperatures is shown in Figure 3.

This observation substantiates thefact that weather patterns may

have a dramatic influence on thesuccess of a prime application.Moist, windy and cloudy conditions can be detrimental in thesuccessful application of prime.

155

Figure 4: Average temperature variation during November 2006

Figure 5: The effect of cloud cover on 23 August 2006

Conclusions

MC 30 cutback bitumen’sperformance as a prime is, apartfrom granular base type anddensity, very dependent ontemperature, since temperaturehas the most direct influence onits viscosity. The viscosityinfluences the ability of theproduct to penetrate the basematerial and any MC 30 cutbackbitumen which does not penetratein the first day will lie on top ofthe base for more than a week, ifnot more.

There are a number of actionsfrom suppliers which may in future solve some of the penetration anddrying time of cutback bitumenprimes. True invert bitumenemulsions will increase successrate, but be careful, conventionalemulsions cannot be used asprimes.

From this study it is evident thattemperature and other weatherconditions will play a significantrole in the success of primeapplications.

The following should be considered to ensure successful primeapplications on site:

• During winter and earlyspring, prime applications are more sensitive to climaticconditions regardless whichprime is used;

• It is preferable to dampen the base with water the nightbefore to achieve the desiredmoisture content;

• Surface tension may bebroken with a lightapplication of water on theday the prime product is tobe sprayed;

• Temperature must bemeasured on site and theroad temperature must be

156

Figure 6: The viscosity-temperature relationship for MC30 cutback bitumen

between 10 and 15°C andrising to give the prime thebest chance to penetratesuccessfully;

• Temperatures should bemonitored from 12h00, andno prime should be appliedafter 14h00 if the roadtemperatures are fallingbelow 15°C, as this willprevent optimumpenetration.

• In summer time, when theovernight temperatures aregenerally above 15°C,cognisance should be takenof shade, wind, cloud coverand rain conditions, as thesemay have a negativeinfluence on the success of aprime application.

Task team

A resolution was passed at theNovember 2006 meeting of theRoad Pavements Forum for Sabitato convene a task team toinvestigate the possible changes to the SANS 308 Specification forCutback Bitumens to overcomeproblems with poor penetrationand slow drying.

Sabita has also issued a newpublication as an interim guideline,

Manual 26 – Interim guidelines for primes and stone precoatingfluids, which identifies alternativeproducts to coal tars for primingand stone precoating, and offersthe practitioner valuableinformation.

Although priming operations areconsidered to be simple, incorrectprime applications may come back to haunt the industry, and canmanifest in the flushing of volatiles through hot mix application in thefirst summer after the construc-tion, leaving binder-rich patches.In seal applications, it may softenthe binders and lead to prematurepunching or bleeding where higher binder applications were specified,especially in single seals.

Although the temperatureinformation in this paper is sitespecific, it is intended to sensitisethe engineers in the contractorand consultant fraternity.

Acknowledgements

The author acknowledges theassistance of Denzil Sadler andHannes Lambert (TechnicalDepartment, Tosas) and Jacquesvan Heerden (Sasol Technology,Fuel Research). q

157

Heavy vehicle overloadinghas been South Africa'snemesis for decades,

despite efforts at moreeffective law enforcement.Overloading causesaccelerated road deteriorationand, together with inadequatevehicle maintenance, driverfatigue and poor driver health,contributes significantly toSouth Africa's poor road safety record.

In July 2003, the forestry industryembarked on a dti/Forestry SouthAfrica-funded project with theCSIR, National ProductivityInstitute (NPI) and Crickmay &Associates to introduce aself-regulation system, the LoadAccreditation Programme (LAP) toaddress overloading, vehiclemaintenance and driver wellnessin the timber transport industry.The initiative was in line with theDoT's National Overload ControlStrategy (NOCS) in which one ofthe recommended interventionswas to explore the concept ofself-regulation and to facilitate

such an industry-led initiative tocomplement law enforcement. The NOCS identified the AustralianNational Heavy VehicleAccreditation Scheme (NHVAS) asone that had a number ofcomponents appropriate to theSouth African situation.

Background

The successful implementation ofLAP in the forestry industry – theextent of overloading in terms ofnumber of heavy vehicles chargedwith overloading dropped by 40%over a two year period – led tovarious stakeholders identifyingthe need to establish a nationalLAP steering committee to expandthe programme to otherindustries. A national LAPworkshop was held in June 2004,during which issues such as thevision, mission, mandate,objectives, structure and terms ofreference of the proposedcommittee were discussed anddebated. Stakeholders andorganisations represented at theworkshop included the NDoT,

159

Towards industry self-regulation:

The development of a RoadTransport Management Systemin South Africa

Paul Nordengen

Research Group LeaderNetwork Asset Management Systems

CSIR Built Environment

SANRAL, Forestry South Africa(FSA), the Institute forCommercial Forestry Research(ICFR), SA Cane Growers(SACGA), Road Freight Association (RFA), NPI and CSIR. The firstmeeting of the national committee was held in July 2004 and one ofthe first tasks was to compile anational LAP strategy.

During the next 12 months various industries were approached with aview to participating in the LAPinitiative, and by the end of 2005,a number of these industries hadindicated their willingness. Theseincluded the Chamber of Mines,Sabita, ASPASA, SARMA, SACGAand the pulp, paper and boardindustry (distinct from the timberindustry).

In November 2005, the nationalsteering committee, which nowincluded new blood, identified theneed to revise the LAP strategydocument, and in particular toconsider the possibility of a namechange, as it was felt that thename “Load AccreditationProgramme” put too muchemphasis on the aspect ofvehicle overloading withoutrecognising other important aspects such as vehiclemaintenance, driverwellness and productivity.

In fact, the issue of thename of the project wasfirst raised and debated atthe initial national LAPworkshop in June 2004, but at that stage it was decided to keep the name. Afterlengthy (and some heated!) debates, the committee

decided to rename the initiativethe Road Transport ManagementSystem (RTMS), and a TechnicalWorking Group was appointed with the task of drafting the new RTMSstrategy.

The RTMS five-year strategy wasofficially launched in October 2006 (Transport month) and in theforeword the Minister of Transport, Mr Jeff Radebe states that “(TheRTMS) is an industry drivenprocess that complementsgovernment programmes aimed at promoting efficient road basedoperations, road infrastructureprotection and road safety. Itherefore commend thepro-activity shown by theleadership of this initiative, andhave no doubt that it will lead totremendous improvement in theperformance of the logisticschain."

Road closures due to accidentsinvolving heavy vehicles have anegative impact on the total costof logistics in South Africa, which

160

Figure 1: An example of accelerated pavementdeterioration caused by heavy vehicle

overloading

is almost double that of the USAand 50% more than Japan andBrazil (as a % of GDP).

The RTMS

RTMS is an industry-led, voluntary self-regulationscheme thatencouragesconsignees,consignors andtransport operatorsengaged in the roadlogistics value chainto implement avehicle manage-ment system thatpreserves roadinfrastructure,improves road safety and increases theproductivity of the logistics valuechain. (This scheme also supportsthe Department of Transport'sNational Freight LogisticsStrategy.)

The RTMS will offer support forimplementation of the followingcomponents:

• National Standards Auditors(accredited by SANAS);

• Tools (manuals, templates,implementation guidelines);

• Information portals (website,data sharing);

• Recognition and concessions;• Promotion (brand promotion

to create meaningfulrecognition among public and industry stakeholders);

• Special projects (selected bythe RTMS stakeholders andare aligned to RTMSobjectives);

• Research and technologyinnovation.

Stakeholders

The RTMS strategy identifies thefollowing stakeholders:

Value-chain:• Consignees,

consignors andtransportoperators;

• Organisedbusiness andindustryassociations;

• Organised labour.

OtherStakeholders:• Government

(Department ofTransport, thedti, Department

of Science and Technology,provincial and localgovernment, SANRAL, lawenforcement agencies, etc);

• Public sector institutions(standards generating bodies, productivity institutions,research institutions).

161

Figure 2: Accidents involving heavyvehicles often lead to road closures, in

some cases causing long delays

The total cost of

logistics in South

Africa is almost

double that of the

USA and 50%

more than Japan

and Brazil (as a

% of GDP)

Standards

The national steering committeeidentified the need to develop thestandards based on a phasedapproach, and the starting pointchosen was the standarddeveloped for the forestryindustry.

Once the SA RTMS nationalstandards have been tried andtested, it is planned that thesestandards will be made availablethrough the SABS for adoption asa harmonised SADC standard. The final phase would be to proposethe standard as the basis for the development of an internationalISO standard for road logistics.The proposed process is shown inFigure 3.

Structure

The proposed RTMS structure isshown in Figure 4. The NationalSteering Committee has beenfunctional since July 2004, and aTechnical Working Group wasestablished in November 2005.There are currently three industrysteering committees (forestry,mining and asphalt).

To date there has also been strong participation and support from theNDoT, SANRAL and theKwaZulu-Natal DoT as well asvarious corporate sponsors andassociations (FSA, ICFR, Chamberof Mines, Sabita, ASPASA, SARMA, RFA).

Development process

In August 2006 the SABS wasapproached to develop the RTMS as a national standard. Through aconsultative process, it was

162

RTMS Vision 2012

RTMS will be a nationally recognised self-regulating scheme forheavy vehicle road transport, resulting in a safe, equitable andcompetitive heavy vehicle logistics value chain.

RTMS MISSION

To provide a national certification scheme (standards, auditors,manuals) and implementation support (information portals,recognition, technology transfer) for heavy vehicle road transport toconsignees, consignors and transport operators, focusing on:

• Load optimisation;• Driver wellness;• Vehicle maintenance; and • Productivity.

163

Figure 3: Envisaged evolutionary process for developing RTMS standards

RTMS standards for transportoperators – Timber

Amended industry-wide standards forconsignors, consignees and transport

operators

Develop new SANS for roadlogistics with SABS

Develop SADC harmonisedstandard

Conveneinternational

ISOcommittee

Develop ISOstandard forroad logistics

Time

Now

6months

18months

3 years

5 – 6years

Certification

Private

Private

SANS

SANSSADCSTAN

ISOSANS

SADCSTAN

Figure 4: Proposed RTMS structure

Government and corporate sponsors

National Steering Committee

Project Manager

Functional teams

Technical workinggroups

Industry steeringcommittees

Experts andspecial interest

groups

decided to first publish thestandards as a “RecommendedPractice” (ARP 067), Part 1 beingthe recommended practice foroperators. A SABS TechnicalCommittee, STANSA TC181B:Road Transport ManagementSystems, was constituted inOctober 2006, and a WorkingGroup appointed to transform theLAP standards developed by theCSIR for the forestry industry intoan SANS Recommended Practice.

The ARP 067-1:2007 Part 1:Operator Requirements – Goodswas published by Standards South Africa in February 2007, and theWorking Group is currentlypreparing Parts 2 and 3 of RTMSstandards for consignors andconsignees.

ARP 067 Part 1 sets minimumstandards for road transportthrough ten rules as follows:

• Maintenance of a haulage fleet inventory;

• Assessment ofthe vehiclemass anddimensionsbefore eachladen trip;

• Verification ofthe massdeterminationmethod;

• Maintenance of vehicles in aroad worthycondition;

• Vehicle and load safety;• Management of driver

wellness;• Training and education;

• Tasks and responsibilities;• Records and documentation;

and• Performance assessments.

Templates will be provided asexamples to assist operators inpreparing for certification, which is achieved through a successfulexternal audit by aSANAS-accredited auditor.

Conclusions

The RTMS is an industry-driveninitiative in co-operation withgovernment, which attempts toaddress issues such asoverloading, load securement,vehicle maintenance, driverfatigue and driver health and theirimpacts on road deterioration,road safety and the cost oflogistics. The pending legislationcovering the responsibilities of

consignors andconsignees withregards heavyvehicle roadtransport will nodoubt have asignificant impacton the nature ofroad transportcontracts. It isanticipated thatconsignors andconsignees will infuture berequired to assumea far greaterresponsibility forthe manner inwhich their goods

are transported on the public roadnetwork. The RTMS is a tool thatcan be used by consignors,consignees and transport

164

Consignors and

consignees will

be required to

assume far

greater

responsibility

for the manner

in which their

goods are

transported

operators as part of their qualitymanagement systems to addressthe current problems in roadtransport, thereby demonstratingtheir commitment to corporategovernance. q

References

National Overload Control Strategy.Department of Transport, March 1994.

S.V. Kekwick 2003. National OverloadControl: Self-regulation of heavy vehicleloading. CSIR Transportek, Pretoria.

Alternative Compliance: National Policy.National Road Transport Commission.1998. Australia.

Mass Management Accreditation Guide.Roads and Traffic Authority. 2000. RTA,New South Wales, Australia.

Maintenance Management AccreditationGuide. Queensland Transport. 2000.Australia.

Forest Engineering Southern Africa, CSIRTransportek, National ProductivityInstitute, Crickmay & Associates. 2004.

Load Accreditation Programme for theTransport Industry. CSIR Transportek,Pretoria.

Road Transport Management SystemFive-Year Strategy 2006. NPI, Midrand,South Africa.

Road Transport Management Systems: Part 1: Operator Requirements – Goods. Standards South Africa. 2007. ARP 067-1,SABS, Pretoria.

165

In late 2005, the Board ofAgrément South Africa approved the Guideline

Document for the Assessmentand certification of thinbituminous surfacing systems1

developed by an industry taskteam2. This developmentfollows the success of otherinitiatives to expand the rangeof road products AgrémentSouth Africa is able toevaluate.

These include, but are not limitedto, the following:

• bridge deck joints (criteriadrawn up in 2001 – eightjoints are currently certifiedincluding two elastomer-modified bitumen plugexpansion joints);

• road additives (criteria drawn up in 2004 – no productscertified to date); and

• thin bituminous surfacings(also termed ultra-thinfriction courses UTFC),defined as proprietarybituminous products with

suitable properties to providea wearing course that is laidat a nominal thickness of upto 40 mm and ispredominantly intended as afunctional layer.

The approval of the guidelinedocument has paved the way formanufacturers of non-standardproprietary UTFC’s to now havetheir products evaluated andcertified as ‘fit-for-purpose’. Oneproactive manufacturer is in thefinal stages of evaluating hissystem which, once successfullycompleted, will result incertification.

Seven stage process

The assessment and certificationprocess is undertaken in sixstages, followed by monitoring, asfollows:

• Assessment of the applicant’s data;

• Assessment of productioncontrol;

• Laboratory testing;

166

The role of Agrément in South Africa:

Accreditation of thin bituminous surfacings in SA

John Odhiambo

ManagerAgrément South Africa

• System installation i.e.application;

• System performance trialsection (if required);

• Certification;• Monitoring.

1. Data assessment: Theapplicant’s data, which shouldinclude general information on theproduct, the product’s trackrecord, available test data,process quality control, and thespecific intended use of theproduct, forms the basis of thesubsequent assessment if found to be acceptable.

2. Production control: It is arequirement of Agrément SouthAfrica that an approved anddocumented quality system, based on the requirements of ISO 9000,be in place to control both themanufacture of constituents and the application process of the thinbituminous surfacing system.

3. Laboratory testing: Testingwill be carried out, wherenecessary, to determine orconfirm characteristics of materials and to gauge aspects ofperformance.

Characteristics of materials aredetermined to confirm thatmaterials submitted for evaluationfall within the agreed or specifiedranges; test values are also usedfor subsequent quality monitoringpurposes.

4. System installation: Systeminstallation will be witnessed tohelp gauge the effectiveness ofthe quality system and theprocedures for the application of

the UTFC. Road tests will becarried out and relevant samplestaken for laboratory testing inaccordance with the test methodsand procedures detailed in theapproved guideline document.These guidelines also lay down,where applicable, requiredperformance levels.

Required levels of performancetake into account the certificationclassification category and trafficloads for which the system isintended.

5. System performance: A trialis required to assess theperformance of the system over aperiod of time, and siteperformance tests will include:

• Visual observation;• Texture depth;• Skid resistance;• Torque bond.

Additional tests may be requireddepending on whetherperformance characteristics areclaimed which are not covered bythe above mentioned tests.

6. Certification: Subject to afavourable assessment, AgrémentSouth Africa will issue anAgrément certificate which will:

• clearly define the system and state the uses for which thesystem has been assessed;

• verify the system’scompliance with the Board’sperformance criteria.

The certificate will also clearlyindicate conditions of certificationand the Board may, at its

167

discretion, impose limitations orrequirements governing the use of the system.

7. Monitoring: One of the mostimportant conditions ofcertification imposed is that thecertificate holder must participatein the Board’s ongoing qualityassurance scheme. This entailsquality surveillance of thecertificate holder by the Agency ofAgrément South Africa on anannual basis, followed by threeyearly certificate reviews.

Ongoing monitoring also facilitates the amendment to theperformance criteria where this isfound to be necessary.

Conclusion

Agrément offers the owners ofproprietary UTFC’s a mechanismto expand the use of theirproducts through increasedacceptance of non-standard

products. At the same time it alsoprovides the road authority withassurance that the product hasbeen certified for a givenperformance level, and that thequality during manufacture andapplication will be carried out interms of an approved qualitymanagement system. Thecertification of UTFC will in thenear future become mandatory onall South Africa National RoadsAgency Ltd (SANRAL) contracts. q

1 A copy of the Guideline Document:The Assessment and Certification ofThin Bituminous Surfacing Systems isavailable free of charge fromAgrément South Africa’s website,www.agrement.co.za . 2 The Board is grateful to the industrytask team whose input facilitated thedevelopment of the guidelinedocument. This team included: Mrs ESadzik, Prof K Jenkins, Messrs MHenderson, P Myburgh, JP Nothnagel, P Olivier, D Pretorius, D Rossmann, G Swart, B Verhaeghe, M Winfield, and J Wise.

168

Notes

169

170

Author Index

Author Page

Bornmann, Francois . . . . . . . . . . . . . . . . . . . . . . 88

Michael Bouwmeester . . . . . . . . . . . . . . . . . . . . . 73

Distin, Trevor . . . . . . . . . . . . . . . . . . . . . . . . . 39

Hiley, Robbie. . . . . . . . . . . . . . . . . . . . . . . . . . 88

Horak, Emile . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Jenkins, Kim . . . . . . . . . . . . . . . . . . . . . . . 82, 138

Jooste, Fritz . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Levin, Mannie. . . . . . . . . . . . . . . . . . . . . . . . . 126

Louw, Kobus . . . . . . . . . . . . . . . . . . . . . . . . . 130

Marais, Herman . . . . . . . . . . . . . . . . . . . . . . . 102

Muller, Johan . . . . . . . . . . . . . . . . . . . . . . . . . 150

Myburgh, Piet . . . . . . . . . . . . . . . . . . . . . . . . . 30

Nordengen, Paul . . . . . . . . . . . . . . . . . . . . . . . 159

Odhiambo, John . . . . . . . . . . . . . . . . . . . . . . . 166

Onraët, John . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Pagel, Deon . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Pretorius, Derick . . . . . . . . . . . . . . . . . . . . . . . 102

Ross, Don . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Rossmann, Dennis . . . . . . . . . . . . . . . . . . . . . . 143

Sadzik, Elzbieta. . . . . . . . . . . . . . . . . . . . . . . . 111

Sampson, Les . . . . . . . . . . . . . . . . . . . . . . . . . 67

Strydom, Stefan . . . . . . . . . . . . . . . . . . . . . . . . 88

Thompson, Hugh. . . . . . . . . . . . . . . . . . . . . . . . 73

Van Zyl, Gerrie . . . . . . . . . . . . . . . . . . . . . . . . 147

Weideman, Alex . . . . . . . . . . . . . . . . . . . . . . . . 28

Winfield, Mike . . . . . . . . . . . . . . . . . . . . . . . . . 61

Wise, Julian. . . . . . . . . . . . . . . . . . . . . . . . . . 119

171

Advertiser Index

Advertiser Page

Colas SA (Pty ) Ltd . . . . . . . . . . . . . . . . . . . . . . 129

Corporate Image Holdings (Pty) Ltd . . . . . . . . . . . . . 60

Engen Petroleum Ltd . . . . . . . . . . . . . . . . . . . . . 137

Holcim SA (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . 27

Kaytech [a division of Kaymac (Pty) Ltd] . . . . . . . . . . 125

More Asphalt . . . . . . . . . . . . . . . . . . . . . . . . . 158

Much Asphalt (Pty) Ltd . . . . . . . . . . . . . . . . . . . . 81

Sasol Wax (a division of SCI Ltd) . . . . . . . . . . . . . . . 87

Spraypave . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Tarfix (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . 101

Tosas (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . 146

Zebra Bituminous Surfacings cc . . . . . . . . . . . . . . . 118

172

Sabita ManualsManual 1 Construction of bitumen rubber sealsManual 2 Bituminous products for road constructionManual 5 Manufacture and construction of hot mix asphaltManual 7 SuperSurf: Economic Warrants for Surfacing

Unpaved RoadsManual 8 Bitumen safety handbookManual 9 Bituminous surfacings for temporary deviationsManual 10 Appropriate standards for bituminous surfacingsManual 11 Labour enhanced construction for bituminous surfacingsManual 12 Methods and procedures – Labour enhanced

construction for bituminous surfacingsManual 13 LAMBS – The design and use of large aggregate

mixes for basesManual 14 GEMS – The design and use of granular emulsion mixesManual 16 REACT – Economic analysis of short-term

rehabilitation actionsManual 17 The design and use of porous asphalt mixesManual 18 Appropriate standards for the use of sand asphaltManual 19 Technical guidelines for bitumen-rubber asphaltManual 20 Sealing of active cracks in road pavementsManual 21 ETB: The design and use of emulsion treated basesManual 22 Hot mix paving in adverse weatherManual 23 Bitumen Haulier’s Code: guidelines for loading

bitumen at refineriesManual 24 User guide for the design of hot mix asphaltManual 25 Quallity management in the handling and transport

of bituminous bindersManual 26 Interim guidelines for primes and stone precoating fluids

Asphalt Academy publications

TG1 Technical Guidelines: The use of modified binders in road construction

TG2 Interim Technical Guidelines: The design and use of foamed bitumen treated materials

Training Guides

TRIP — Technical Recommendations in PracticeHMA — Hot Mix Asphalt Training seriesHSE — Health, Safety and Environmental Guidelines for bitumen and coal tar productsCEP — Councillor Empowerment Programme

173

Sabita Video Training Aids

Video series on testing of Bituminous Products

Bitumen

AV-1 Penetration test / Softening point (ring and ball)AV-2 Spot test / Rolling thin film oven testAV-3 Brookfield viscosity / Ductility

Bitumen Emulsion

AV-4 Sayboldt furol viscosity / Water content of emulsionsAV-5 Sedimentation value of emulsions / Residue on sievingAV-6 Coagulation value with chippings / Coagulation value

with Portland cementAV-7 Binder content of slurry / Particle charge test

Hot mix Asphalt

AV-8 Optimum binder content for asphaltAV-9 Marshall testAV-I0 Binder content / Moisture contentAV-11 Static creep test / Immersion indexAV-12 Rice’s density and binder absorption/Bulk relative

density and voids

Bitumen Rubber

AV-13 Ball penetration and resilience test / Dynamic viscosityAV-14 Compression recovery / Flow testAV-15 Bulk density of crumb rubber / Grading and loose fibre

test of crumb rubber

Video series on Blacktop Roads

AV-22 Black-top surfacing and repair (with Instructor Training Manual)

AV-23 Pavement surfacing and repairs for black-top roads

Video series on Hot mix Asphalt

AV-25 ManufactureAV-26 PavingAV-27 Compaction

Health, Safety andEnvironmental ConservationAV-28 BitSafe – The safe handling of

bitumen (DVD)

For order informationcontact Sabita at:

info@sabita.co.za

174

Sabita Members

Ordinary Members

AJ Broom Road Products (Pty) LtdAkasia Road Surfacing (Pty) LtdBitumen Construction Services (Pvt) LtdBitumen Supplies & Services (Pty) LtdBlack Top Holdings (Pty) LtdBP SA (Pty) LtdBrisk Asphalt Surfacing (Pty) LtdChevron South Africa (Pty) LtdColas SA (Pty) LtdEngen Petroleum LtdJavseal (Pty) LtdMilling Techniks (Pty) LtdMore AsphaltMuch Asphalt (Pty) LtdMurray & Roberts Construction LtdNational Asphalt (Pty) LtdNikamandla Construction (Pty) LtdNyanga Roads (Pty) LtdPhambili Road Surfacing (Pty) LtdPolokwane Surfacing (Pty) LtdRand Roads (a division of Grinaker-LTA Ltd)Roadsmart (Pty) LtdSasol Oil (Pty) LtdShell SA Marketing (Pty) LtdSpray Pave (Pty) LtdTarfix (Pty) LtdTarspray ccTosas (Pty) LtdTotal SA (Pty) LtdVan Wyk Tarmac ccZebra Bituminous Surfacing cc

175

Associate Members

Africon Engineering International (Pty) LtdArcus Gibb (Pty) LtdAsch Professional Services (Pty) LtdBCP Engineers (Pty) LtdBKS (Pty) LtdCape Peninsula University of TechnologyDick King Lab Supplies (Pty) LtdEntech Consultants (Pty) LtdGMH/CPP Consulting Engineers (Pty) LtdGoba (Pty) LtdHHO AfricaHolcim SA (Pty) LtdIliso Consulting (Pty) LtdJeffares and Green (Pty) LtdKaymac (Pty) Ltd t/a KaytechLafarge South Africa LtdLidwala Consulting Engineers (Pty) LtdNinham Shand (Pty) LtdPD Naidoo and Associates (Pty) LtdRankin Engineering ConsultantsSasol Technology Fuels ResearchSasol Wax (a division of SCI)Siyenza Engineers ccSpecialised Road Technologies (Pty) LtdStewart Scott International (Pty) LtdTshepega Engineering (Pty) LtdUnitrans Fuel and Chemical (Pty) LtdVaal University of TechnologyVela VKE Consulting Engineers (Pty) LtdWSP SA Civil and Structural Engineers (Pty) Ltd

Affiliate Members

Beosumbar and Associates ccDMV Harrismith (Pty) LtdMTTC (Pty) LtdSalphalt (Pty) LtdThe Synthetic Latex Co (Pty) LtdTPA Consulting cc

Notes

176