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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.doc
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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.xls
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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.doc
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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.doc
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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.xls
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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


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