Bitumen Emulsion Workshops

Bitumen Emulsion Workshops

A EUROPEAN VIEWPOINT ON BITUMEN EMULSIONS W.T. Hulshof

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BITUMEN EMULSION WORKSHOP

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A EUROPEAN VIEWPOINT ON BITUMEN EMULSIONS

0 Drs. W.T. Huishof, Development Manager, Akzo Chemie, Armak Chemicals

ABSTRA CT

. A review is given comparing the status of cutback bitumen versus bitumen emulsion usage in the different countries in Western Europe. The function of cationic surfactants as adhesion agent and bitumen emulsifier is explained. Cationic bitumen emulsions are dominantly used in surface dressing and the aspects of this technology are discussed in detail. The testmethods for bitumen emulsion and their relationship with practice is given. A survey on W-European emulsion specifications is included. Tack coat emulsions, slurry seal emulsions and future expectations are briefly discussed.

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HUTJSHOF, A EUROPEAN VIEWPOINT ON BITUMEN EMULSIONS

INTRODUCTION

The manufacture of bitumen emulsions in W-Europe started in the early fifties and developed - due to stimulation from industry and government - into a large industry with many relatively small production units spread all over Europe. The transport costs related to the watercontent of the emulsion as well as intensive competition in bidding for road repair or construction have covered all of Europe with a web of emulsion factories. There are clear differences between the many European countries regarding preferred road construction and maintenance techniques which make bitumen emulsion application different from one country to another.

In the early development days bitumen emulsions replaced cutback bitumen. The advantages of using cationic bitumen emulsions are obvious. Bitumen emulsions are easier and safer to use than hot cutback bitumen. They can be readily stored and require less energy in application compared to cutback bitumen. They are less hazardous than cutback bitumen, since they use water and non-volatile diluents in their manufacture. Cationic bitumen emulsions can be produced with high stability and can be transported and used without premature coalescence of the bitumen particles.

Cationic bitumen emulsions, unlike anionic emulsions, can be used with wet or damp aggregates. They develop adhesion rapidly between bitumen and aggregate. Due to the widening recognition of their technical advantages, cationic bitumen emulsions are being increasingly used with excellent results in surface dressing, tack-coating of wet aggregates, sealing of gravel sub-bases and in slurry seals and have replaced anionic emulsions almost everywhere in Europe.

The best estimate on the quantity of bitumen emulsions produced in 101 W-Europe in 1984 is 2.5 million tonnes of which approximately seventy to

eighty percent is used in surface dressing applications. Approximately three hundred emulsion manufacturing units exist all over Europe to produce the needed quantity of emulsions. Thousands of people are employed to cope with bitumen emulsions used in maintenance and repair.

The following summary indicates what the different countries are doing:

Cutback Bitumen Bitumen Emulsion

Norway (2) 90% 10% Sweden (5) 70% 30% Denmark (2) 90% 10% U.K. (25) 20% 80% Holland (15) 30% 70% Germany (25) 30% 70%

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Belgium (8) 80% 20% France (100) 10% 90% Spain (20) 20% 80% Italy (5) 80% 20%

In brackets you will find the approximate amount of emulsions produced compared with France in percentages. So if France produces I million tonnes (mt) per year, the U.K. produces 0.25 mt per year.

2. CATIONIC SURFACTANTS 0 The use of cationic surfactants plays a dominant role in cutback bitumen applications as well as in bitumen emulsions. The simple fact that water can prevent a thorough bonding between bitumen and aggregate and also can displace a bituminous binder from an aggregate surface is sufficient to consider the use of cationic surfactants in bitumen applications such as used in road construcion.

Adhesion plays an important role in surface dressing. Water and pumping effects, traffic, temperature cycling, and bitumen oxidation, deterioration and stress cracking determine the life time of a surface dressing. Stripping in the surface dressing can proceed in three steps:

Water goes through weak spots in the bitumen coating and penetrates the aggregates.

Water occupies the surface and parts of the aggregate by forcing the bitumen back and off the surface. Stripping starts.

The bitumen only covers small parts of the surface and finally loses its bond to the aggregate. Stripping is fully developed.

Cationic adhesion agents secure a physico-chemical bond between aggregates and bitumen binder. The cationic eniulsifier used in bitumen emulsions plays the role of 'built-in' adhesion agent if the emulsion breaks on the aggregate surface.

For cutback bitumen it is common to add sufficient adhesion agent to secure immediate adhesion between aggregate and binder as well as raquired longlife properties for the surface dressing mat. Laboratory tests will monitor the required quantity of adhesion agent used in cutback and in W-Europe two test methods are widely spread:


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U.K. TRRL Wet Tray Test - active adhesion test. Aggregates are dipped through a water layer into the cutback bitumen (200 secs, BS 3690). After ten minutes the aggregates are removed from the binder and the percentage of binder retained on the chippings is assessed visually. The presence of a good cationic adhesion agent in the binder will give a displacement of water from the aggregate surface and so bind the bitumen to the aggregate surface.

French LCPC testmethod - passive adhesion test. Cutback bitumen at operation temperature (100-4300C) is mixed with dried aggregates giving 5% residual bitumen onto the aggregates. After air curing at 200C for 24 hours the coated aggregates are divided in two parts:

put under water for 16 hours at 200C, requirement: mm. 90% coating left; put under water for 16 hours at 600C, requirement: min. 75% coating left.

This test could be inodif Led to aa acti'ie adhesion test if prewetted aggregates are used and the cutback bitumen operation temperature is lowered.

3. CATIONIC BITUMEN EMULSIONS IN SURFACE DRESSING

A comparison between cutback bitumen and cationic bitumen emulsions applied in surface dressing can be summarised as follows:

(a) Application of bitumen emulsions in surface dressing is more critical than with cutback bitumen.

Failures with cutback bitumen mainly happen, if material is sprayed at too low temperatures.

The viscosity of the binder is then too high to wet the aggregate surface properly resulting in lack of adhesion.

Failures with bitumen emulsions in surface dressing happen if the break through of the emulsion is not sufficient. The emulsion which stays in between the aggregates breaks via a water elimination path (sun, wind). It is responsible for the lack of early build-up of strength of the mozaic embedding. In colder climates especially this can be a problem and the cause of failures.

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BITUMEN EMULSIONWORKSHOP

Cutback bitumen usually gives earlier strength to chipping embeddings in the binder compared to bitumen emulsions.

In hilly areas cutback bitumen is mainly used. The explanation is that a fast increase in the viscosity of the binder will better secure a fixing of the chippings in binder.

Ecological reasons cause bitumen emulsions to get preference. The loss of cutback solvent to the atmosphere is wasting energy. In Europe no restrictions exist. In some states in the U.S.A. there is a strong lobby to switch to environmentally acceptable bitumen emulsions. The U.S. Transportation Research Board calculated that for the production of cutback bitumen approx. 12,000 MJ per ton are used and for the 40 production of emulsion approx. 1,100 MJ.

From the point of view of economy, cutback bitumen meets approximately the cost/performance of bitumen emulsions. Bitumen emulsions contain 30-35% water, approximately 0.2% emulsifier, 0.2% auxiliary chemicals. They require the investment in an emulsion factory. The estimated depreciation costs for a 5,000-10,000 tons factory are approximately Dfl. 0.10/kg (US $ 0.04/kg emulsion).

It is obvious that for the ultimate choice of cutback bitumen versts bitumen emulsion application diverse points can be considered.

The ultimate goal of surface dressing appitcation is to obtain a well formed surface dressing mat consisting of a closed mozaic of aggregates embedded into a bitumen layer. Only a complete mozaic structure is able to resist the displacement forces of traffic rolling over it and cars breaking on the road. Commonly a closed mozaic structure is one layer of aggregates with a void content of approx. 50%. The aggregates are thrown into the bitumen film and the final mozaic structure results after passing of the roller. Ultimately the traffic will finalise the mozatc Formation and its strength build-up during the first days of the new surface dressing mat. In the early hours of the freshly laid mozaic the structure is most vulnerable against unexpected forces (car braking and cornering at high speed). If time passes the void content of the surface dressing mat will decline to approx. 30% and highest mozaic strength is achieved (Fig 1).

BITUMEN EMULSION WORKSHOP 51

V1 ry'v'v -y -v V V YV V V V

Binder needed to fix the sprayed aggregates.

Texture depth Filling of Road

B

.4 .-.. After spraying of aggregates

C

t -Y -' —

After rolling

III

Cured surface dressing flat

Fig 1 - Evolution of a surface dressing treatment

For every surface dressing job a quantity of hinder is prescribed. The applied volume of binder depends on the amount of volatiles present which is different for bitumen emulsion and cutback bitumen. If a surface dressing mat has achieved a status of stability after several months, the residual volume of binder is respOr1sLble For the proper functioning of the bitumen-aggregate iaoaic and there should be sufficient structure depth. A quantitative comparison is as follows:

1 kg Bitumen emulsion, 67% bitumen with density 1.030 kg/rn3 results in

065 liter residual binder

1 kg cutback bitumen, 88% bitumen with density 1.000 kg/rn3 results in

088 liter residual binder

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In order to achieve the quantity of residual binder in the mozaic mat it is necessary to apply 135 kg bitumen emulsion compared to 10 kg cutback bitumen.

The surface dressing passes during curing two critical periods:

An initial period during which the surface dressing mat must survive on the basis of adhesion and cohesion whilst the aggregates are giving insufficient support to each other. This is the case La the first few days.

The consolidation period during which the mozaic on the road obtains its definitive structure. 0

In surface dressing the road is sprayed with a cationic bitumen emulsion and then covered with mineral aggregates. The emulsion should be stable during storage and transport but breaking should occur as quickly as possible after gritting. Emulsion breaking mechanism starts with the adherence of (positively charged) bitumen droplets onto (negatively charged) aggregate. Following this setting and curing follows resulting in the increase of the surface dressing mat cohesive strength.

Between the aggregates residual emulsion has to lose water by evaporation and will pass through an intermediate stage of emulsion droplet coalescence called 'the cheesy state' (7). In this stage no cohesive strength is available and slow traffic or rolling can be very advantageous since the mechanical actions may lead to disruption of the interdroplet films and coalescence can prOceed. Wind and temperature will do the rest to overcome the cheesy state. The choice of right quality of emulsion is often underestimated. Only a perfectly balanced emulsion is able to reduce the time and appearance of a cheesy state to the utmost minimum and so to improve the quickest increase of the cohesive strength of the surface dressing mat. The proper choice of catiociic eniilsiiier and bitumen emulsion recipe are the basics behind this emulsion technology.

To improve the strength of the surface dressing mozaic it is practised to apply a so called double surface dressing. First approx. 15 kg/rn2 cationic bitumen is sprayed onto the road. Immediately 9 Lu 10 kg/rn2 aggregates 8/11 mm follow. Rolling follows. The spaces between the large aggregates arefilled. Second 07 to 08 kg/rn2 emulsion is sprayed followed by 7 to 8 kg/rn2 aggregates 2/6 mm. A final rolling follows (Fig 2).


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1st treatment: 8/11 mm aggregates

2nd treatment: 2/6 mm aggregates

0 Fig 2 - Double surface dressing To improve the cohesive strength polymer modified binders are used

in the manufacture of cationic bitumen emulsions. The function of the polymer in the bituminous binder is to increase the elasticity, to reduce the brittle point and to improve the binder ductility resulting in earlier retention strength for the aggregates. Under heavy duty circumstances polymer modified binders have proven their validity and are more and more considered as general purpose application in order to improve the quality standard of our road net work.

4. TEST METHODS

Sophisticated testmethods have been developed to monitor the application of . bitumen emulsions. In 1981 a report was presented to the technical

committee RILEM at a meeting in Zuerich made by Mr. U. Isacsson, National Swedish Road and Traffic Research Institute, summarizing fifty different testiaethods for bitumen emulsion used throughout the world. In this wood of testpossibilities it is necessary to be selective.

The right testinethod should be as near as posstble to practice and a forerunner to those demands met later practice. Possibly tests should be simple, low in costs and test materials should be used similar to those used later in practice.

A review of the specification of the three nato emulsion producing countries France, Germany and the U.K. reveals already the local differences present in W-Europe.

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Property Appendix Class of cationic road emulsion

K1-70 K1-60 K1-40 K2 1(3

Residue on 710 mi BS sieve (% by mass maximum) C.l - 0.05 0.05 0.05 0.05

Residue on 150 mi BS sieve (g per 100 ml maximum C.2 - 0.15 0.15 0.15 0.15

Binder contents (minimum % by mass) E 67 57 38 57 56

Viscosity (' Engler 200C) F.1 - 6-9 4 max. 10 max. 10 max.

Viscosity Redwood No. II (s at 850C) F.2 25_35* - - - -

Coagulation of emulsioi at low temperature G - nil nil nil nil

Storage stability (short period test) (inversions to clear sediment) H.l - 60 60 60 60

Storage stability (long period test) (cater content difference % maximum) H.2 - 2 - 2 2

Particle charge J positive positive positive positive positive

Fig 3 - Properties of cationic road emulsions (U.K.) 10

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Rapid Medium Slow Property Testmethod

Class Class Class

60% 65% 69% 60% 65% 69% 55% 60%

Watercontent NF T 66-023 39 41 34 36 30 a 32 39 41 34 a 36 30 a 32 44 a 46 39 a 41

Viscosity Engler at 250C 2 15 > 6 - > 2 > 6 - < 15 2 15

Viscosity STV at 250C (diameter 4 mm) NF T 66-020 - - ) 9 < 18 - > 9 - - Homogenity:

- particles above 063 mm NF T 66-016 < 01 < 01 < 01 < 01 < 01 < 01 < 01 < 01

- particles between 063 mm and 016 mm < 025 < 025 < 025 < 025 < 025 < 025 < 025 < 0'2

Storage stability via decantation T 66-022 < 5 < 5 < 5 < 5 < 5 < 5 < 5 < 5

Adhesion:

- emulsion stored max. 15 days: 1st test

2nd test NF T 66-018 90

>, 75 >, 90 >, 75

90 . 75

>, 90 . 75

90 . 75

> 90 >, 75

- -

- -

- emulsion stored 15 days to three months 75 . 75 > 75 >. 75 > 75

Breaking index NF T 66-017 < 100 < 100 < 100 80 140 80 140 80 140 > 120 > 120

Cement mixing stability NF T 66-024 - - - - - - - - Particle charge NF T 66-021 positive positive positive positive positive positive positive positive

H C

m z m

C

0 z 0

Cl, I 0 -ti

Fig 4 - Cationic emulsions (FRANCE)

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Nr. Requirements U 60 K U 70 K Testmethod DtN

1 Particle charge cationic 52044

2 Appearance brown, 52002 homogenous liquid

3 Water content, max. weight 7 42 32 52048

4 Sieve residue, max. weight % 05 05 52040

5 Storage stability 52042 Sieve residue: after 4 weeks, max. weight % 05 after 1 week, max. weight % 05

6 STV measurement 52023 4 mm orifice at 200C, max. sec 12 part 1 4 mm orifice at 400c, max. sec 60

7 Penetration binder B 300 to B 80

8 Properties of the reclaimed binder 52041 ash max. weight Z 25 25 52005 Softening point max. °C 49 49 52011 Ring and Ball min. °C 27 27

9 Breaking index, max. g 200 200 52047 part 1

10 Waterinfluence on bitumen coated aggregate Aggregate 52006

completely part 1 coated

Fig 5 - Unstable cattonic bitumen emulsions (GERNANY)


The most commonly applied testuiethods will be desribed briefly.

4.1 BREAKING OF BITUMEN EMULSION

The breaking of bitumen emulsion in contact with aggregate is of utmost importance. Best approximation towards practice is the in France developed 'breaking index testmethod' which has been taken in a slightly modified way by Germany (DIN 52047).

A well defined aggregate being siliceous fine aggregate is added at a rate of 03-05 g/sec through a funnel to 100 g emulsion in a 100 ml . beaker. Addition of siliceous fines continues till the emulsion thickens and

finally forms an isolated ball not adhering to the glasswall being characteristic for the break of the emulsion. The German testmethod differs in the way of dosing the siliceous fines. Every ten seconds 5 g of fines are added with a spoon and the emulsion is stirred with a spoon till a ball forms. The quantity of used siliceous filler is a relative measure for the to be expected speed of break of the emulsion. For example, Duomeen T tallowpropylene diamine is compared with Redicote N39L, the liquid formula-tion of propylene diamine:

Quantity of TP diamine in kg Ibreaking index per ton emulsion (g of siliceous fines)

16 tallowprop.diamine 80 25 tallowprop.diamine 80 < b.i. < 120 60 tallowprop.diamine > 120

18 Redicote N39L 76 18 Duomeen T Emulsifier 119

4.2 ADHESION OF BITUMEN BINDER TO AGGREGATE

The adhesion of bitumen binder to aggregate is secured by the use of the right cattonic emulsifier giving a strong, irrevesible bond between binder and aggregate. Most widely spread is the method of the LCPC, the French Road Testing Institute established in Paris, involving a relatively quick and simpLe assessment of the bond bitumen-aggregate.

The LCPC adhesion test involves mixing 100 g aggregates with emulsion such that a 5% residual quantity of bitumen binder remains behind on the aggregate surface. After thorough mixing the coated aggregates are left behind for 24 hours at 200C to cure. The coated aggregates are divided in two parts:

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put under water for 16 hours at 200C, requirement: mm. 90% coating left; put under water for 16 hours at 600C, requirement: mm. 75% coating left.

This test could be modif Led to an active adhesion test if prewetted aggregates are used.

4.3 STABILITY OF EMULSION

The stability of the emulsion regarding transport can be imitated with a shake stability test. The shake stability test is carried out by taking a sample of each emulsion (50 g) in 250 ml bottle and shaking it for 1 and 2 10 hours at 275 strokes I minutes in a desplacement of 25 cm. The bottle contents are filtered through a 250 micron sLeve and the residue of broken material recorded.

Typical results to be expected:

Emulsion breakage

1 hour % 2 hours

Emulsion 1 s s Emulsion 2 9 Emulsion 3 3 Ii Emulsion 4 2 2

s = severe breakage in bottle

This method has been used to compare the quality of different cationic emulsiflers. For example, bitumen eiiulsLfters made with a varying amount of emulsifier and at different pH's can behave different in this shake stability test. In this way an indication about 'the strength' of cationic emulsifier can be obtained.

Not mentioned but at least of the same importance are bitumen emulsion viscosity and settlement. All European specifications require these properties with a slightly different number.


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Summarizing we can say that the inatri testmethods for cationic bitumen emulsions, in particular rapid setting emulsions, are:

Method Description Specification

Breaking indx Kixtng siliceous fines with. LCPC, Special W, 1974 emulsion till break DIN 52047, part 2

Breaktinie Mixing aggregate and emulsion -- till break

Passive adhesion Mixing emulsion and aggregate. LCPC, Special W, 1974 Immersion in water at 200C and Synd.des fabr.em., 600C and assessment of coating 1976

Binder content incl.solvent: Dean+Stark BS 434 (I) no solvent: 1200C, evaporation

Settlement 100 ml cylinder, to record LCPC, Special W, 1974 after 7 days waterlayer at top

Viscosity Engler BS 434 (I) Brookfield, RVT 100 rpm --

Sieve Residue BS 434 (I), DIN 52040

Shake stability! 2 hours shaking Essai de brassage,

stability to LCPC

transport

Fig 6 - Testmethods for cationic bitamen emulsions

5. TACK COAT EMULSIONS

Bitumen emulsions with binder content varying from 33% to 60% are specified throughout W-Europe. An important emphasis for the specified cationic bitumen emulsions used as tack coat is to secure a storage stability of minimum one year. Tack coat emulsions are often sprayed directly from a drum which means that they can stand a long time aside before being used and must survive a waiting-before--use during a winterstorage period.


Far reaching is the W-Gernian specification which is laid down as follows:

Lfd. Nr.

Requirements tack coat emulsions Testing acc. DIN

I Charge to be mentioned 52044

2 Appearance brown, homogenous, 52002 liquid

3 Watercontent, max. weight % 60 52048

4 Sieve residue, max. weight % 05 52040

5 STV viscosity 52023 4 mm orifice, 200C, max. secs 6 part 1

6 Weight loss after evaporation, 52045 max. weight % 75 part 2

7 Softening point Ring and Ball 52045 on residual binder, mm. 'C 37 part 2

52011

8 Waterinfluence on coated aggregate completely 52006 aggregate coated part 1

9 WettinigabLlity, max. minimally 20 52046

Fig 7 - Solvent containing tack coats

In particular the wetting abLitty For tack coat emulsions raises interest. The idea is that a high quality tack coat emulsion must be able to wet dust and f tries eFFiciently. A test (DIN 52046) is developed where upon the emulsion must penetrate a well defined mixture of siliceous sand and Fines within a certain time. In this way solvent containing tack coat emulsions are made such that TO g eaulston can penetrate 100 g sand + fines within 20 minutes.

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6. SLURRY SEAL EMULSIONS

Slurry sealing started in the U.S.A. in the early sixties and came there upon to W-Europe. As a technically sensitive technology failures appeared in the early days of introduction and became a drawback for the practical development. In most W-Europeari countries slurry sealing has been a small item in road maintenance. The exception is Spain where the warner climate helps very much to obtain the fast cure needed for a proper slurry sealing of an abraded road surface.

The drawbacks for slurry seal application have been the lack . of wearing propert:tes of the thin, bituminous layer as well as

vulnaribility during the first hours open to traffic.

The incorporation of polymers in the bitumen binder, the use of precisely selected aggregates and chemical manipulation to achieve 'instant-cure' of a slurry seal mat have made that slurry sealing is coining back to the road maintenance scene. In particular the Snid and Hollarider slurry seal system (Holland) and the Raschig Ralumac system (W-Gerinany) have attracted wide attention. Nowadays it is possible to lay slurry seals on high speed motorways which are open to the traffic within 10-20 minutes after application.

7. THE FUTURE

Cutback bitumen has been replaced largely by bitumen emulsions, a process which will continue slowly in the next years.

Cationic bitumen emulsions are for certain to stay in use the way it is at this moment. Rapid setting emulsions perfornarice will be further improved following the optimisation of process conditions as well as choice or improvement of cationic emulsifiers.

Slurry sealing has started a comae-back and will gain more attention in the coming years.

Polymer modified binders are more and more used to solve particularly difficult jobs and applied in heavy-duty circumstances. It is very much doubtful that polymer modified binders will achieve a real sizable market compared to conventional bitumen binders because the advantages under ordinary circumstances still have to be proven.

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REFERENCES

Bitumen road emulsions (anionic and catthric) specification. BS 434: part 1, 1984

Bitumen road emulsions (anionic and cationic) code of practice for use. BS 434: part 2, 1984

Recommendations for surface dressing, TRRL, Road Note 39, HMSO, 1972

AJOUR, A.M., 'Chemical aspects of the formulation of bitumen emulsions', Bulletin Liaison Labo. P. et Ch., 1977

A basic asphalt emulsion manual, published by the Asphalt Emulsion Manufacturers Association, Washington, 1979

'Bituminous Emulsions for Highway Pavements', National Cooratives Highway Research Programme 30, Transportation Research Board, Washington, 1975

TAUSK, R.J.M. cs, The setting mechanism of cationic emulsions in contact with mineral aggregates. Colloids and Surfaces, 3 (1981) 1.3-36

AFNOR, Tour Europe Cedex 7, Paris: 3pctFications Emulsions de bitume, NF T-65-011, October 1984

Fachverband der Kaltindustrie, Richweg 23, Norderstedt: Strassenbau mit Bitumenemulsionen, 1983

LCPC, Paris: Les Emulsions de bitume, Special W, June 1974

LCPC, Paris: l'Essais d'adhesivtte, March 1973

Syndicat des fabricants d'emulsions routieres de bitume, 52 Champs-Elysees, Paris: les emulsions de bitume et leures applications routieres, 1976.

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