The document discusses different materials used in pavement construction such as soil, aggregates, bitumen, cement, and recycled materials. It describes their properties and how they are characterized through laboratory experiments and field testing. Key parameters considered include loads, climatic conditions, and material behavior in response to stress, strain, temperature, time, and moisture levels. Materials can exhibit linear, nonlinear, elastic, plastic, or viscous properties depending on the magnitude and duration of loads. Common tests discussed are CBR, plate load, and penetration tests to evaluate the strength and load-bearing characteristics of pavement materials.

1. Characterization ofPavementMaterials:
Bitumen used in pavement construction is temperature dependent,
visco- elastic characteristics and fluid like behavior. Bitumen is the end
productgetting from the refineries. Differenttypes of material are used in
differenttypes of Pavement.
1) Soil, 2) Aggregate (Natural/artificial) 3) Bitumen, Tar, Emulsion,
Cutbacks 4) modified bituminous binders (Polymer and rubber) 5)
Bituminous mixes. 6) Cement 8) Cement concrete ( Plain,
reinforced or prestressed ) 9) Stabilizing materials 10) Recycled
materials 11) Geo-textiles/geomembrane.
Characteristics of Materials:
1) To classify/ grade
2) To obtain inputs for designof new pavement
3) To obtain inputs regarding condition of the materials in an existing
pavement.
4) To ensure properquality during construction.
Pavement materials properties are evaluated by conducting
laboratory experiment on representative samples.
By field evaluation and by estimation.
Parameters consideredforcharacterization of pavement are:
1) Loads (Stationery/moving, heavy/light application mode (normal &
shear, impact)
2) Climatic condition (temperature, rainfall, moisture)
3) Weathering condition (wetting/dying, chemical action, freeze)

2. Material behavior generally depends on
1) Stress-strain relationship.
2) Ability of material to recover after release of load
3) Temperature dependency
4) Time dependency.
For example, this stress strain diagram of a given material can be
represented by a straight line, such behavior is considered as linear but
stress-strain relationship in pavement is not linear and it can take the
any differentshape and described as non-linear.
When the load is released the material regain its own position and this is
known as ‘elastic deformation’, but in some cases sometimes it could not
be able to regain completelyits original position, so permeant
deformationhas been developedthis is known as ‘plastic deformation’.
Sometimes materials exhibit partly recoveryand partly permanent
deformationor plastic properties which is called ‘elastoplastic’
deformation.

3. Under constant stress if the strain does not change with time then it is
considered as ‘non-viscous’ materials whereas for a constant stress if
strain goes on varying then this is known as ‘viscous’ materials.
So, materials used in pavements are the following types:
1) Linear/non-linear
2) Elastic/Plastic
3) Viscous/Non-Viscous
4) Combination of these.
Material behavior depends on :
1) The magnitude, Time/frequencyand nature of load.
2) Temperature to which the material is subjected to
3) Moisture level.
Approximate loading time depends on
1) Speed of the vehicle
2) Size of the tyre imprint ( Load contact area)
3) Load spreading capabilities of the pavement layers
4) Position of the elementunder consideration.

4. Due to loading time the behavior of materials will be different.Some
materials is subjected to short loading time, some materials in the
bottom layers have long loading time.
Testcondition for PavementmaterialEvaluation:
To obtain properties that are relevant for a given situation, the
following aspects to be considered forfield laboratory evaluation.
1) The magnitude, Time/frequencyand nature of load.
2) Temperature to which the material is subjected to
3) Moisture level.
4) Degree of compaction.
Soil:
Soil used in the embankment portion for construction of Pavement
and also soil found in Subgrade and Shoulders of a pavement in
natural form or processed or stabilized form.
Soil has Index and Mechanical properties.Soils are classified on the
basis of particle size distribution and index properties.
Indian Classification of Soil:
Coarse grain> 50% larger than 0.075mm sieve.
Fine grain> 50% smaller than0.075mm sieve.
Gravel 80mm to 4.75mm
Sand 4.75mm to 0.075mm
Silt & Clay < 0,075mm ( 0.075mm to 0.002mm Silt and <0.002mm is
clay usually on the basis of LL & PL.
Index Properties:Atterberg Limits ( Liquid Limit, Plastic Limit &
Shrinkage Limit).
Solid Semi-Solid Plastic Liquid
SL. PL LL
As per water content
Liquid limit is defined as the minimum water content at which soil will
flow when subjected to a very small shearing force.

5. Liquid limit (LL) is determined by cutting groove in the soil paste placed
in a cup. The moisture content corresponding to the trail in which the
groove closes after 25 drops of the cup is the LL.
Plastic Limit is the minimum water content at which the soil remains in
plastic state. Stage at which the soil can be rolled into a thread of 3mm
diameter without crumbling.
Plasticity Index (PI) = LL- PL ( Range of water content at which soil can
remain in plastic stage.)
Water content required to saturate the soil when the total volume
remains unchanged.
Shrinkage Limit: Shrinkage limit is the maximum water content at which
further reduction in water content does not cause reduction of volume.
Soil Classification: 1) Textural classification 2) Unified classification 3)
BIS classification 4) HRB or AASHTO classification.
Textural classificationof soil is very simple method commonly not used.
Unified Classification: Based on gradation and Atterberg limit coarse
grained soils ( >50% retained on 0.075mm sieve)
G= Gravel, S=Sand. C=Clay W= well graded, P= Poorly graded.

6. GW= well graded gravels, SP= poorly graded sand, SC= clayey sand.
Fine grained soils ( >50% passing 0.075mm sieve)
M= Silt, C=Clay O= Organic, L= Low plasticity, H= High Plasticity,
ML= silt of low compressibility,CH= High compressibilityClay,
CG=clayey gravel, SW= well graded sand.
Indian system (BIS) classificationis very similar to unified classification.
HRB or AASHTO Classification:
HRB ( Highway ResearchBoard) system of classificationis based on
both the particle size distribution as well as the plasticity characteristics
of the soil. A characteristic group index is used to describe the
performance of soils when used for pavement construction.
The AASHTO Soil ClassificationSystem was developedby the
American Associationof State Highway and Transportation Officials,and
is used as a guide for the classificationof soils and soil-aggregate
mixtures for highway construction purposes.
In Group Index method soil grouping is made A-1 to A-7.
A-1 group with GI value of ‘0’ are coarse grained, low plasticity soil
considered excellentforsubgrade.
A-7 group fine soils with high plasticity ( GI value upto 20) poormaterials
for subgrade.
Soil Strength:
Factors influencing soil strength.
Soil Type: granular soil usually have better strength compared to fine
grained soil.
Particle size distribution: Determine the internal friction and cohesion.
Degree of compaction:Greatly influence the strength. Soils with greater
degree of compactionreduces the possibilityof settlement.
The degree of compactionattainable varies with soil and it is a function
of moisture content and the compactive effortused.
Moisture content affects the density, cohesionand internal friction.
Granular materials are stronger when they are confined.
Shear Test (Shear Box, Triaxial shear test) is conducted on laboratory
samples under specified condition(Loading, compaction,drainage).
Bearing Tests---Usually conducted in field by Plate Loading.
Penetration Tests:Measure resistance of soil samples to the penetration
of a standard plunger.

7. Plate Load Test
The Plate Load Testis done to determine modulus of subgrade reaction
used in design of concrete pavement. The diameter of bottom plate is
760mm.
If Bearing Pressure is P for obtaining settlement of , then
Modulus of subgrade reaction (k) = P/ 
California Bearing Ratio (CBR):
CBR is the ratio expressed in percentage of force per unit area required to
penetrate a soil mass with a standard circular plunger of 50 mm diameter
at the rate of 1.25 mm/min to that required for corresponding penetration
in a standard material. The ratio is usually determined for penetration of
2.5 and 5 mm . When the ratio at 5 mm is consistently higher than that
at 2.5 mm, the ratio at 5 mm is used.
Soaked sample is taken of 152mm dia. And 127mm height, the
penetration of the plunger 1.25mm/minute and the resistance by the
sample is recorded.

8. The following table gives the standard loads adopted for different
penetrations for the standard material with a C.B.R. value of 100%.
Penetration of Plunger (mm) Standard Load (MPa)
2.5 6.895
5.0 10.343
The C.B.R. values are usually calculated for penetration of 2.5 mm
and 5 mm. Generally the C.B.R.value at 2.5 mm will be greaterthan
at 5 mm and in such a case/the formershall be taken as C.B.R. for
designpurpose.If C.B.R.for5 mm exceeds thatfor2.5 mm,the test
should be repeated. If identical results follow, the C.B.R.
corresponding to 5 mm penetration should be taken for design.
CBR =
Load carried by the specimen
Load carried by standard crushed stone specimen
X 100
Drawback of CBR Test:It is an empiricalformula; the fundamental
behavior has not been evaluated. Presence of coarse materials (size
20mm)affects the result.