pavement materials in road construction

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Page 1: Pavement materials in Road Construction

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PAVEMENT MATERIALS

Page 2: Pavement materials in Road Construction

IntroductionPavement subjected to various conditions

Weather changesImpact loadsImposed loads etc.

Should not undergo excessive deformation and settlement

Differential settlement – failure of pavementHence, high compressibility and plastic

properties are not desirable for pavement construction

Good quality soil is required

Page 3: Pavement materials in Road Construction

Pavement Cross sectionConsists of different layers

EmbankmentSubgradeSubbaseBaseWearing course

Different types of materials are used depending on the layer requirement.

Page 4: Pavement materials in Road Construction

Soil is the main constituent in Subgrade and embankment

Aggregates are used in the Sub base and base layer

Aggregates and binding material in the top layerSub grade and embankment provides support

for the pavementDifferent types of failures such as rutting and

shoving in the flexible pavements, cracking in the rigid (concrete) pavements are due to poor subgrade soil.

Page 5: Pavement materials in Road Construction

SoilAccumulation or deposit of earth material

formed by the disintegration of rocksDesirable Properties:

StabilityIncompressibilityPermanency of strengthMinimum change in volumeGood drainageEase of compaction

Page 6: Pavement materials in Road Construction

Index Properties of SoilThe soil properties based on which

identification and classification are done are known as index properties.Grain Size DistributionLiquid limitPlasticity Index

Grain size distribution is determined by mechanical analysis

Liquid limit by Casagrande apparatus

Page 7: Pavement materials in Road Construction

Grain Size distributionCoarse grained soils by

Sieve analysis (for non-cohesive soils) – sieving material successively through smaller sieves.

for cohesive soils – wet sieve analysisSoil fines by

Sedimentation analysis – hydrometer method, pipette method.

Gradation characteristics can be obtainedi.e., proportion of different soils i.e., sand,

gravel, silt, clay etc can be found out.

Page 8: Pavement materials in Road Construction

Grain Size Distribution Curves

Page 9: Pavement materials in Road Construction

Consistency Limits and Indices•Atterberg limits are the limits of water content used to define soil behavior.

Page 10: Pavement materials in Road Construction

Soil typesBased on the particle size and propertiesDifferent types are thereClassification is primarily based upon

Grain Size distributionIndex Properties

Based on the grain size, soils are classified as below.GravelSandSiltClay

Page 11: Pavement materials in Road Construction

Different Systems of ClassificationUSGSTextural Soil ClassificationBurmister MethodCasagrande Soil ClassificationUnified Soil Classification SystemBISHRBAnd a lot more… But all classifications do

not have a common sizes for defining soil class.

Page 12: Pavement materials in Road Construction

Unified Soil ClassificationDeveloped By Casagrande in 1948Airfield construction - world war IIModified to suit the reqt of other

constructionsAccording to USCS

Coarse grained soils –> (grain size distribution): More than 50% retained on 75micron

Fine grained soils –> (plasticity characteristics): More than 50% passes through 75micron

Page 13: Pavement materials in Road Construction

USC SystemGravel – More than 50% on sieve no: 4 (4.75mm)Sand - More than 50% passes sieve no: 4 (4.75mm)Coarse grained contains <5% fines – well graded

(GW, SW)Poorly graded – GP, SPFor more than 12% fines – GM, GC, SM etc.For Fine grained soils

LL is 50% or less – ML, SL etc (soils of low compressibility)

MH, SH etc., - LL more than 50% ( soils of high compressibility)

Highly organic soils are termed as peat

Page 14: Pavement materials in Road Construction

USCS

Page 15: Pavement materials in Road Construction

Indian Standard Soil ClassificationSimilar to USCSDifference is w.r.t fine grained soils

Sub divided into 3 categories – low, medium and high compressibility

Total 18 types of soilsSymbols used are same as USCS

Page 16: Pavement materials in Road Construction

Indian Standard Soil Classification

Page 17: Pavement materials in Road Construction
Page 18: Pavement materials in Road Construction

Tests on SoilFor evaluating the properties of soilStrength, Stiffness etc are studiedShear testsBearing TestsPenetration tests

Page 19: Pavement materials in Road Construction

Shear TestsCarried out on the small samplesPerformed in the laboratoryDirect Shear testsTri-axial compression testUn-confined compression test

Page 20: Pavement materials in Road Construction

Bearing TestsCarried out on the subgrade soilsInsitu testsLoad bearing areaResults vary with the properties of the soil

under the testPenetration test is a small scale bearing test

Size of loaded area is smallRatio of penetration to size of loaded area is

largeCan be insitu or laboratory

Page 21: Pavement materials in Road Construction

California Bearing Ratio Test (CBR)Developed by the California Division of

HighwayFor classifying and evaluating the Soil sub

grade and base course materials for flexible pavements

It is an empirical testCannot be related directly with the

fundamental properties of the soilUsed to determine material properties for

pavement design

Page 22: Pavement materials in Road Construction

CBR denotes the measure of resistance to penetration of pavement material or soil, of standard plunger under controlled conditions.

Conducted in laboratory on re-moulded specimens. (undisturbed samples can also be used)

Procedure for determining CBR value is standardized by various agencies including BIS.

Page 23: Pavement materials in Road Construction
Page 24: Pavement materials in Road Construction

Plunger of 50mm1.25mm/minute penetrationLoad reqd. for penetration of 2.5mm and 5.0mm

are recorded.CBR value is expressed as the percentage of the

standard load value in standard material.For 2.5mm penetration

Standard load = 1370kg, unit standard load = 70kg/cm2

For 5.0mm penetrationStandard load = 2055mm, unit standard load =

105kg/cm2

Page 25: Pavement materials in Road Construction

CBR TestSpecimen in mould is compacted to maximum

dry density (OMM)IS heavy compaction as per IS: 2720 part VII for

heavy traffic roadsIS light compaction for low traffic roadsThe specimen subjected to soaking for 4 daysSwelling and water absorption are notedThen weight is placed on the top of specimen

in the mould.Assembly is placed under the plunger of the

loading frame.

Page 26: Pavement materials in Road Construction
Page 27: Pavement materials in Road Construction

Reasons for Initial Concavity of shapeTop layer of the soaked soil is too soft after soakingTop surface of soil not evenPlunger is not verticalPlunger arrangement is wrongNormally penetration value at 2.5mm is higher than

5.0mm. And higher value is recorded as CBR.Average of 3 test specimens have to taken as the

value.Presence of coarse grained particles result in poor

reproducibility of resultsMaterial passing through 20mm sieve is only used

in the test.

Page 28: Pavement materials in Road Construction

PLATE BEARING TEST

Page 29: Pavement materials in Road Construction

Plate Bearing Test – ApparatusBearing Plates – 750, 600, 450 and 300mm

dia and 15 to 25mm thicknessA loading device consisting of hydraulic

jack and proving ring arrangement or pressure gauge

Reaction frame for giving thrust to plates.Datum frame and dial gauges are used to

measure settlement of loaded plate.

Page 30: Pavement materials in Road Construction

Plate Bearing Test - ProcedureTest site is levelled and plate is seated

properly on the surfaceFor modulus of subgrade reaction of natural

ground – top soil upto 20cm is removed. Stiffening plates of decreasing dia are

placedJack and proving ring assemble is fitted3 to 4 dial guages are fixed on the

periphery of plates

Page 31: Pavement materials in Road Construction

Plate Bearing Test – ProcedureA pressure of 0.07kg/cm2 (320 kg for 75cm dia plate)

is applied and removed after few secondsDial readings are noted corresponding to zero loadLoad applied by means of jack, to cause a settlement

of 0.25mmWhen no increase in settlement or when the rate is less

than 0.025mm/min the load dial reading and settlement readings are noted down

Average values are consideredNext, load is increased so the settlement will be

0.25mm extraThis way experiment is repeated upto 1.75mm or

more.

Page 32: Pavement materials in Road Construction
Page 33: Pavement materials in Road Construction

Modulus of subgrade reaction is the reaction pressure sustained by the soil sample under a rigid plate of standard diameter per unit settlement measured at a specified pressure or settlement.

IRC specifies that the K value be measured at 1.25 mm settlement.

K = p/0.125 (kg/cm2/cm)

Page 34: Pavement materials in Road Construction

Allowance for Worst Subgrade MoistureK value will be lowest at soaked conditionMoisture content during test may seldom

represent worst condition at siteK value obtained is modified by a factor to

represent the worst condition2 consolidation test specimens are prepared1 sample tested in un-soaked condition in lab

– pressure – deformation curve drawn (pressure for 0.125mm is noted)

2nd specimen soaked

Page 35: Pavement materials in Road Construction

Pressure required to produce same deformation is noted (ps)

ThenKs = K Ps/P

Page 36: Pavement materials in Road Construction

Correction for smaller plateSome cases not possible to cause

settlement of 0.175cm for the 75 dia plateSmaller dia plate will be usedObtained K1 value is modifiedAssuming subgrade as an elastic medium,

where modulus of elasticity is ∆ = 1.18pa/EBut , K = p/ ∆ = E/1.18aIf E is constant for a soil, Ka = K1a1 => K

= K1a1/a

Page 37: Pavement materials in Road Construction

AggregatesObjectives

Role of aggregatesSource of aggregatesProperties of aggregatesTests on aggregates

Page 38: Pavement materials in Road Construction

IntroductionCombination or group of particle massesUsed with binding medium92-96 percent of bituminous concrete70 -80 percent of cement concrete

Page 39: Pavement materials in Road Construction

SourcesNatural

Obtained from large rock formation by quarrying

Excavated rock is crushed to obtain aggregates of different sizes

ManufacturedBy product of industriesBrick ballast

Page 40: Pavement materials in Road Construction

Classification on Natural AggregatesIgneous

Cooling of magmaCrystalline in structureGrain size classification, composition based

classificationSedimentary

Formed by various depositsClassified based on predominant mineral

MetamorphicFormed from igneous or sedimentary

Page 41: Pavement materials in Road Construction

Desirable propertiesClean and free of clay and organic matterBe angular and not flaky

Page 42: Pavement materials in Road Construction

Desirable propertiesClean and free from clay and organic matterStrengthHardnessToughnessShapeAdhesion with bitumenDurabilityBe non- absorptiveBe resistant to abrasion on exposure to trafficFreedom from deleterious particles

Page 43: Pavement materials in Road Construction

Chemical Properties of aggregatesImportant for bituminous and cement

concrete mixesSurface chemistry decides how well bitumen

adheres to aggregatePoor adhesion results in stripping causing the

failure of pavementsIn PCC pavements, if reactive silica is present

in aggregates it reacts expansively with cement paste. Causing expansion, which leads to cracking and other types of failures.

Page 44: Pavement materials in Road Construction

Stripping of aggregatesOne of the main failure modes in

bituminous pavementsDue to loss of adhesionWater affinity ( hydrophilic or hydrophobic)

Page 45: Pavement materials in Road Construction

Alkali-aggregate reactionThis is main mode of failureChemical reaction between aggregates and

hydroxyl ions a associated alkalis in the cement

Concrete deterioration is slow but progressive

Depending on the type of minerals present in the minerals these reactions and resultant decay varies

Page 46: Pavement materials in Road Construction

Physical properties of aggregatesGradation and sizeToughness and abrasion resistanceDurability and soundnessParticle shape and surface textureSpecific gravitycleanliness

Page 47: Pavement materials in Road Construction

Gradation and SizeEffect of gradation and size in bituminous

mixesWorkabilityLayer thicknessThickness of liftStabilityStiffnessResistance to deformationFatigue strengthdurabilityPermeabilitySurface texture and frictional resistance

Page 48: Pavement materials in Road Construction

Physical properties – gradation and sizeEffect of gradation and size in bituminous

mixesStrengthDimensions of structural elementw/c ratioStabilityDurabilityWorkabilityFatigue strengthshrinkage

Page 49: Pavement materials in Road Construction

Strength, Hardness, ToughnessSubjected to

Stress action due to wheel loadWear and tearCrushing

HardnessConstant rubbing and abrasionHard enough to resist the abrasive action

caused by trafficToughness

Resistance to impactEx: jumping of steel wheels

Page 50: Pavement materials in Road Construction

Shape, Adhesion, DurabilityRounded, cubical, angular, flaky or

elongated shapeFlaky and elongated particles will have less

strengthShould have less affinity with waterOther wise stripping will occurWithstand adverse weather actionAlso called as soundnessShould be clean and free from organic

matter

Page 51: Pavement materials in Road Construction

Aggregate testsCrushing test Abrasion test Impact testSoundness testShape test Specific gravity and water absorption testBitumen adhesion test

Page 52: Pavement materials in Road Construction

Crushing TestTesting aggregate against compressive stressIS:2386 Part – IVProvides a relative measure of resistance to

crushingSpecimen in the mould is subjected to gradual

loadDry aggregates passing through 12.5mm sieve

and retained on 10mm sieveFilled in cylindrical mould of 11.5 mm dia and

18cm heigh3 layers tampered each 25 times

Page 53: Pavement materials in Road Construction

Crushing TestTest sample is weighed (w1) and placed in

cylinderCompressive load of 40 tonnes applied at a

rate of 4 tonnes per minuteCrushed aggregates are sieved through

2.36mm sieveWeight of material passing the sieve is

measured (w2)Aggregate crushing value = (w1/w2)x100< 10 indicates strong aggregateAbove 35 means weak

Page 54: Pavement materials in Road Construction

Abrasion testTo test the hardness property of aggregatesLos Angeles abrasion test is usedStandardized by BIS, IS:2386 Part IVPrinciple is to find the percentage wear due to

relative rubbing action between aggregate and steel balls

Consists of a steel drum (dia 700mm, length 520mm)

Abrasive charge – steel balls of dia 48mm and weight 350 to 450 gms are placed inside the cylinder

No of spheres to be used depends on the grading of sample

Page 55: Pavement materials in Road Construction

Abrasion testQuantity depends on gradation ( 5 to 10kg)Cylinder rotated at around 33-35 rpm for

500 to 1000 rotationsMaterial is sieved through 1.7mm sievePassed amount is expressed as percentage

of total aggregate weightThis is called los angeles abrasion value.

Max values are,For WBM – 40Bituminous concrete - 35

Page 56: Pavement materials in Road Construction

Impact testResistance to impact of aggregatesAggregates passing 12.5 mm sieve and retained on 10

mm sieveFilled in a cylindrical steel cup of internal dia 10.2 mm

and depth 5 cmMaterial filled in 3 layersMetal hammer of weight 13.5 to 14 kgs is arranged to

drop with a free fall of 38cm in vertical directionTotal blows are 15Crushed aggregate is passed through 2.36mm IS sieveAggregate Impact value = Expressed as ratio of total

weightMax value for: WBM is 40, Bituminous concrete is 35

Page 57: Pavement materials in Road Construction

Soundness testTo evaluate resistance to weathering actionAccelerated weathering test cyclesAggregates of specified size are subjected to

cycles of alternate wetting in a saturated solution of either sodium sulphate or magnesium sulphate for 16 - 18 hours and then dried in oven at 105 − 110C.

5 cyclesLoss in weight is determined by sievingLoss in weight should not exceed 12 percent

when tested with sodium sulphate and 18% when tested with magnesium sulphate solution.

Page 58: Pavement materials in Road Construction

Shape testsThe particle shape of the aggregate mass is

determined by the percentage of flaky and elongated particles in it.

The flakiness index is defined as the percentage by weight of aggregate particles whose least dimension is less than 0.6 times their mean size.

The elongation index of an aggregate is defined as the percentage by weight of particles whose greatest dimension (length) is 1.8 times their mean dimension. (applicable only to aggregates larger than 6.3mm)

Page 59: Pavement materials in Road Construction

Specific gravity and water absorptionSpecific gravity of an aggregate is considered to

be a measure of strength or quality of the material

Absorption properties also indicate the strength. More porous rocks are weak in nature.

Test Procedure:2 kg sample of aggregate is washed and drained,

kept in wire basket.Immersed in distilled water at temperature 22 to

32 C with water cover atleast 50mm.Trapped air is removed by dropping the basket

for 25 times at a height of 25mm from the bottom.

Page 60: Pavement materials in Road Construction

And weight of basket and aggregates is noted in immersed condition. (W1).

Then they are removed from water and allowed to drain for few minutes.

Aggregates kept in a dry water absorbent clothEmpty basket moved back to water, jolted 25

times, weight is W2.Then aggregates moved to another dry cloth

and again dried for 10 to 60 minutes.Weight of surface dried aggregate = W3Aggregate kept in oven at 110 C for 24 hours.Cooled and weighed. (W4)

Page 61: Pavement materials in Road Construction
Page 62: Pavement materials in Road Construction
Page 63: Pavement materials in Road Construction

Bitumen adhesion testBitumen adheres well to all normal types of road

aggregates provided they are dry and free from dust

Adhesion problem occurs when the aggregate is wet and cold

the presence of water causes stripping of binder from the coated aggregates

Static immersion testThe principle of the test is by immersing

aggregate fully coated with binder in water maintained at 400C temperature for 24 hours.

IRC has specified maximum stripping value of aggregates should not exceed 5%.

Page 64: Pavement materials in Road Construction

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