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8/12/2019 Bituminous Mixes
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PARAMOUNT CONSTRUCTION
COMPANY Ltd.Hincon house, Vikhroli (west),
LBS Marg., Mumbai 400 083
KUMUD SHASHIKA SENEVIRATNE
B.Tech (CIVL)
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To understand
Properties of bituminous mix ingredients
Mix design as per Marshall method The limitations of Marshall method
Importance of other methods of mix design
OBJECTIVES
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Bitumen
Aggregate
Filler (R/filler or External filler) Modifiers
Ingredients
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Hydraulic binders
Lime
Cement
Gypsum
Bitumen Tar
Hydrocarbon binders
Tar
Bitumen
Binders
Bitumen
What is Bitumen ?
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TAR
It is a by-product in theprocess of destructivedistillation of coal for procuringcoke
Maximum use was up to 1955 More adhesive with aggregate
More susceptible to the temp.variations
Get oxidized and become brittlemuch quicker
Life of surface is very less
Bitumen
It is residue obtained inthe process of distillationof petroleum crude atthe refineries
Availability is very muchhigher than tar
Less susceptible to thetemp. variations
Life of surface is betterthan tar
Bitumen
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Bitumen Constitution :
Bitumen is a complex chemical mixture of
molecules that are predominantly hydrocarbons
with a small amount of structurally analogous
heterocyclic species and functional groupscontaining sulphur, nitrogen, and Oxygen atoms.
Typical elemental analysis:
Bitumen
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Bitumen
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Bitumen
Bitumen is broadly divided into two
chemical groups
1. Asphaltenes
2. Maltenes
a. Saturates
b. Aromatics
c. Resins
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Elution with toluene
/ methonol
ResineAromaticsSaturates
Filiter
Silica gel /
Alumina,
Chromotography
Elution with
toluene
Precipitate of
Asphaltenes
Solubles In-solubles
Bitumen
n-heptane precipitation
Bitumen
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Bitumen
Asphaltenes :
Insoluble in n-heptanes and black or brown in
colour
Contains mainly carbon and hydrozen, and some
nitrogen, sulphur and oxygen
Molecular weight is very high ranging from 600
to 3000000
It plays a major role in rheological properties ofthe bitumen
Solids in state
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Bitumen
Resins :
Largely composed of hydrogen and carbon and
contain small amounts of oxygen, suphur and
nitrogen.
Dark brown in colour and solid / semisolid
These are dispersing agents or peptisers for the
asphaltenes.
Polar in nature and hence highly adhesive.
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Bitumen
Aromatics :
Contains lowest molecular weight naphthenic
aromatic compounds in the bitumen and
represent the major portion of the dispersion
medium for the peptized asphaltenes Constitute 4065% of total bitumen
Consists non-polar carbon chains and high
dissolving ability Average molecular weight 300 to 2000
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Bitumen
Saturates :
Non-polar viscous oils
White in colour
Average molecular weight is similar to that of
aromatics.
This fraction forms 5-20 % of the bitumen.
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Bitumen
Asphaltenes :
Increase the asphaltenes:
More harder bitumen
More viscous
Lower penetration
Higher softening point
Higher viscosity
Asphaltenes varies from 525 % in the
bitumen
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Bitumen
Increasing aromatic: little effect on rheological
properties
Increasing the saturates: softens the bitumen
Addition of resins: harden the bitumen, increasing
the viscosity, reduce the penetration index
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Bitumen
Durability :
It is an ability of the bitumen to maintain
satisfactory rheology, cohesion and adhesion in
long-term service.
Ageing : because of oxidation bitumen getsharden
Aging Index
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Bitumen Tests on Bitumen :
Parameter Range
Specific Gravity IS:1202 Min = 0.99
Penetration IS:1203 Pen 60-70
Ductility IS:1208 cm min. 75
Softening Point IS:1205 oC 40-55
Water IS:1211 % by mass max. 0.2
Flash PointIS:1209, IS
1448oC Min 175
Paraffin wax Content IS:10512 % by mass max. 4.5
Loss on Heating, TFOT IS:1212 % by mass max.1
Matter soluble in
trichloroethylene
IS:1216 % by mass min. 99
Frass Breaking Point IS:9381 Depend on grade
Penetration Ratio % min. 35
Absolute Viscoc ity at 60oC IS 1206 Part 2 Poises 1000+200
Kinematic Viscocity at 135oC IS 1206 Part 3centistokes
(cst)Min 150
Retained penetration after TFOT IS 9382 % Min 52
Test Standard
ACCEPTANCE CRITERIA, PAVING BITUMEN -TYPE 1, GRADE S65 *
Specification
* As per MOST and IS:73
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Bitumen
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Mix design Methods
Marshall Method
Hveem Method
Refusal Density Method Superpave method
Film Thickness Method
Etc.
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Most commonly used method and Why?
Marshall Method
Simple technique
Simple, inexpensive, and portable equipment
Less time consumable
Mix design Methods
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Characteristics of Marshall method:Unconfined test and maximum failure load in the
test is recorded as stability.
Shortfalls in Mrashall method:
It measures merely the adhesive strength ofbitumen-filler mortar. Ex: sand heap, M20 vs M80
Strength due to angel of internal friction is not
reflected in this testIt can not predict the fatigue behavior of the
bitumen.
Irrespective of traffic its design blows are 75 only
Mix design Methods
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Shortfalls in Mrashall method:It is unconfined but at field it is not so
Empirical and parameters are not directly related
to field performance (Deformation, Fatigueresistance etc.)
Wide range of grading limits
It doesn't explain about easily compactable mixes
Compaction (Impact method)
It doesnt guarantee the minimum air voids
Mix design Methods
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SUPERPAVE MIX
Due to above said limitations there has a
growing feeling among the Highway
engineers, Which led them to this
Superpave mix
This method can measure the fundamental
properties like fatigue, rutting and low
temperature resistance.
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Developed by Strategic Highway Research
Program(SHRP) , USA
This is also recommended by Federal
Highway Administration(FHWA). This method consists of
1. Selection of material
2. Selection of design aggregate structure3. Selection of design asphalt binder content, and
4. Evaluation of moisture susceptibility
SUPERPAVE MIX
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Notes for Design :
Filler to binder ration : 0.6 to 1.2
Air voids : 3 to 5 %
Min. VMA w.r.t. nominal maximum size
VFB w.r.t. traffic volume
Asphalt film thickness : 6 to 8 mic.
Superpave Mix Design Criteria.doc
SUPERPAVE MIX
http://localhost/var/www/apps/conversion/Local%20Settings/Temp/Superpave%20Mix%20Design%20Criteria.dochttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/Superpave%20Mix%20Design%20Criteria.doc8/12/2019 Bituminous Mixes
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1. Selection of materials:
Binder : PG64-22
Aggregate:
Restricted zone in aggregate grading.
SUPERPAVE MIX
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It specifies the detailed grading limits which givesbetter quality mixes. Restricted zones ofgradation is specified based on the maximumnominal size of the aggregate in the mix.
The mix design which by-pass this restricted zoneshall always gives better results with respect toworkability stability and surface texture etc.
Restricted zone
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Sieve size
in mm
For 37.5 mm nomi.
Size(% passing)
For 25.0 mm nomi.
size(% passing)
For 19.0 mm nomi.
size(% passing)
4.75 34.7 34.7 39.5 39.5
2.36 23.3 27.3 26.8 30.8 34.6 34.6
1.18 15.5 21.5 18.1 24.1 22.3 28.3
0.600 11.7 15.7 13.6 17.6 16.7 20.7
0.300 10.0 10.0 11.4 11.4 13.7 13.7
Restricted zones for diff. Nominal max. sizes
Restricted zone Contd
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Importance of restricted zone:
The restricted zone has been specified toensure adequate aggregate structure isdeveloped in the mixture.
Gradation requirements specify that mixesmust plot either above the restricted zone orbelow the restricted zone.
Gradation control points on the 2.36 mmsieve control the amount of sand sizedparticles in the mixture.
Restricted zone Contd
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Importance of restricted zone: The upper control point limits the sand, in
the mixture to exclude sand-asphalt mixeswhich are quite difficult to compact.
The lower control point ensures adequatesand in contained in the mix to ensure adense graded mixture.
Mixes which passes above the restrictedzone will tend to be sandier and have aweaker aggregate structure than mixeswhich pass below the restricted zone.
Restricted zone Contd
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Importance of restricted zone: Mixes which pass below the restricted zone are gap
graded.
They develop an aggregate structure with the load
carrying capacity provided by the large aggregateparticles.
Sand size particles play more passive role.
If additional sand is added, then the gradation will
enter into the restricted zone, and sand particlewould begin to separate the coarse aggregateparticles reducing the load carrying capability of themixture.
Restricted zone Contd
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Importance of restricted zone: Which structure can bear more load?
Below therestricted zone
Through & abovethe restricted zone
Gap graded Dense graded
Restricted zone Contd
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Maximum density line :Maximum density
P = 100X(d/D)0.45
where P = Total % passing given sieved = Size of sieve opening
D =Max. size of aggregate
(mentioned in sieve size)
See Sheet restrictedzonein
BC-ID 9 for presentation.xls
Maximum density line
http://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xls8/12/2019 Bituminous Mixes
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0.45 power chart
Nijboer, a person working for Bureau of Public Roadsin Netherlans was done lots of investigation and foundthat the densest configuration occurs for a straightline gradation plotted on a 0.45 power chart.
This is also recommended by Federal HighwayAdministration(F HWA).
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It is a graphical representation of sieve sizes raisedto power 0.45 in x-axis and % passing in y-axis.
This curves are helpful in making necessary
adjustments in mix designs. The grading line matching with this line gives the
mix, which is having maximum density and min.VMA.
The air voids of the mix shall become very low thatis why this type of mix can not be used.
0.45 power chart contd..
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The line deviates from this either finer side orcoarser side shall make a mix having more air voidsand adjustment can be done based on therequirements.
To determine the line easily just draw a line from% passing the 0.075mm sieve to the sieve firstpassing 100%
It is always advisable to avoid the design gradingwhich matches the maximum density grading line.
0.45 power chart contd..
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Grading chart with all details
0
20
40
60
80
100
0.01 2.01 4.01Sieve sizes raised to 0.45 power
%a
gepassin
g
spec LL
spec UL
max densityrestric LL
restric UL
BC9
BC 7
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It places consensus requirements on CA and FAangularity, flat and elongated particles, and clay
content
Aggregate Requirements.doc
SUPERPAVE MIX
http://localhost/var/www/apps/conversion/Local%20Settings/Temp/Aggregate%20Requirements.dochttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/Aggregate%20Requirements.doc8/12/2019 Bituminous Mixes
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2. Selection of design aggregatestructure :
Determine few trials blending proportions
With approximate OBC prepare moulds withsuperpave Gyrator Compactor
Check for air voids
Prepare two loose specimens for Gmm.
Check the design criteria
Superpave Mix Design Criteria.doc
SUPERPAVE MIX
http://localhost/var/www/apps/conversion/Local%20Settings/Temp/Superpave%20Mix%20Design%20Criteria.dochttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/Superpave%20Mix%20Design%20Criteria.doc8/12/2019 Bituminous Mixes
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3. Selection of design asphalt binder content:
Using the above selected blending
proportions prepare specimens at at-leastfour different asphlat contents and check for
OBC.
OBC is the binder content at which the air
voids become 4% at the design number ofgyrations.
4. Evaluation of moisture susceptibility:
SUPERPAVE MIX
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SUPERPAVE MIX
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Film Thickness
Bitumen content: which project consumes more bitumen per cu.m.?
PROJECT A% bitumen inDBM 4.2%
PROJECT B% bitumen inDBM 4.0%
Density : 2.450 g/cc Density : 2.680 g/cc
102.9 kg/ cu.m 107.2 kg/ cu.m
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Film Thickness contd..
WHY SO MUCH DIFFERENCEIN DENSITY???
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Film Thickness contd..
Right or wrong???Binder content in DBM:
Min. 4.0% by wt. Of total mix.
RockA
RockA
RockB
Volume : 1 cu.m. Volume : 1 cu.m.Specific gravity : 2.45 Specific gravity : 2.95Bitumen required =
2.45X4/100 = 98kg/cu.m
Bitumen required =
2.95X4/100 = 118 kg/cu.m
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Coating thickness??
Bitumen is not to increase the volume
It may require to give adequate coat to the
aggregate.
RockA
RockB
Film Thickness contd..
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Conclusions:
It may be wrong perception to express the
bitumen content based on the total weightof mix.
Another method to arrive at optimum
bitumen content Asphalt film coatingthickness
Film Thickness contd..
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OBC based on Asphalt film thickness:% binder content = 100 x A x t x rb
where
A = surface area of the aggregate,m2/kg
t = Asphalt film coating thickness, m
rb= Unit weight of asphalt, kg/m3
Calculation of A :
BC-ID 9 for presentation.xls
Film Thickness contd..
http://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xlshttp://localhost/var/www/apps/conversion/Local%20Settings/Temp/BC-ID%209%20for%20presentation.xls8/12/2019 Bituminous Mixes
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Film thickness at OBC
for SGC = 7.5 mic.
For Marshal specimen = 9.5 mic
Super pave gives0.7% less bitumen than that of Marshall OBC
60% higher fatigue life
25% higher rutting resistanceAs considerable asphalt is saving it is also cost
effective.
Conclusions
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SGC is non-portable
Requires well trained laboratory people
Super pave compaction at lab can not be
achieved at lab manually.
However, as it is simulating the siteconditions and performance of the mix is
very much better with respect to fieldperformance parameters, It is advisable tofollow this design criteria.
Limitations
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Any Questions ????
**********
Thank you