Pavement Materials Bitumen

Contents
 Introduction
 Types
 Properties
 Tests on Bitumen
 Grading of Bitumen

Introduction
 Used in pavements
 Binding material
 Used in
 wearing course
 Primer
 Patch works
 Surface dressing etc.,
 Bitumen, Tar are not same.

Bitumen and Tar
 Black or dark colored solid, viscous
cementitious substance.
 Bitumen is petroleum product – obtained
by distillation of crude petroleum or
naturally available in asphalt.
 Coal tar – by product in destructive
distillation of coke

Bitumen and Tar
 Bitumen
 Excellent Binding properties
 Good water proofing surface
 Tar
 Highly temperature susceptible
 Pollutant
 Poor adhesion in presence of water
 Bitumen preferred over Tar

Bitumen - Definition
According to ASTM -
“Bitumen is hydrocarbon material of either
natural or pyrogenous origin found in
gaseous, liquid, semi-solid or solid form
and is completely soluble in carbon-di-
sulphide , carbon tetra chloride”

Bitumen - Intro
 Definition
 At normal range of temp – semi solid state
 When heated viscosity decreases
 For construction of pavements – heated
from 130 to 175C
 Mixing with aggregates at high temp – Hot
bituminous mix
 Mixing with aggregates at low or normal
temperature – Cold bituminous mix

Grades of Bitumen
 Bitumens can be majorly classified into
2 types
 Paving grade bitumen: Used for construction
of roads and airfields
 Industrial grade bitumen: water proofing of
structures and industrial floors etc.,

Types
 Paving grade bitumen
 Modified bitumen binders
 Cutback bitumen
 Bitumen Emulsion

Cutback bitumen
 To have fluid consistency at normal
temp, with low heating – cutback
bitumen is used
 Dilution of paving grade in volatile
solvents – kerosene, light fuel oil etc.,
 Hardening rate depends on the grade
and characteristics of bitumen and
solvent.
 RC, MC, SS

Cutback bitumen
 RC is recommended for surface
dressing and patchwork.
 MC is recommended for premix with
less quantity of fine aggregates.
 SS is used for premix with appreciable
quantity of fine aggregates.

Bitumen Emulsion
 To get fluid consistency
 Dispersing bitumen globules in aqueous
solution (i.e., water with dispersing
agent)
 60% water, remaining bitumen
 Cold bituminous mix
 Properties depend on grade, water
quantity, emulsifier
 RS, MS, SS

Modified Bitumen Binders
 To improve the properties of bitumen
 Additives are mixed
 Polymer modified bitumen is used only
in wearing course depending on the
severity of climatic and weather
conditions

Advantages of modified
bitumen
 Lower susceptibility to daily and seasonal
temperature variations
 Higher resistance to deformation at high
pavement temperature
 Better age resistance properties
 Higher fatigue life for mixes
 Better adhesion between aggregates and
binder
 Prevention of cracking and reflective
cracking

Functions of Binders
 Used in surface course
 Used in base course depending on
traffic
 Used in preparation of mixes
 Used as prime coat over granular base
course
 Used in soil stabilization
 Sealer material for filling joints, cracks in
cc pavements

Requirements
 Adequate viscosity
 Heating bitumen, aggregate
 Cutback
 Emulsion
 Sufficiently viscous on cooling – compact
surface with no deformation
 Form thin film around aggregates
 Sufficient ductility
 Temp susceptibility
 Adhesion with aggregates in presence of
water
 affinity between the materials used in the mix

Tests on Bitumen
 Penetration test
 Ductility test
 Softening point test
 Specific gravity test
 Viscosity test
 Flash and fire point test
 Float test
 Water content test
 Loss on heating test

Penetration test
 Measures hardness or softness of
bitumen
 Measures penetration depth in tenths of
a millimeter to which a standard loaded
needle will penetrate in 5 sec
 Standardized equipment – BIS
 Penetrometer device – consists a
needle, weight of 100g, device for
releasing and locking position

Penetration test setup – Rough
diagram

 Bitumen heated to pouring consistency
 Placed in containers to a depth i.e.,
min15mm excess of expected
penetration
 Conducted at 25C
 Highly fluctuated with small inaccuracy
 Results are used for grading the
bitumen i.e., 40/50 or 80/90 etc.,
bitumens

Ductility test
 It is the property that permits bitumen to
undergo great deformation without
breaking
 Ductility is defined as the distance in cm,
to which a standard sample or briquette
of the material will be elongated without
breaking

 The bitumen sample is heated and
poured in the mould assembly placed on
a plate
 Cooled in air and then kept in waterbath
at 27C
 Sides are removed
 Attached to a machine
 Minimum ductility is 75cm

Softening point test
 Ring and Ball
 Temperature at which the bitumen attains a
particular degree of softening
 Brass Ring containing test sample
 Suspended in liquid (water, glycerin etc.,)
 Heating @5C/Min
 Softening point denotes the temp at which
bitumen touches the base metal plate.

Specific Gravity Test
 Used for classification
 Density influenced by chemical
composition
 Using pycnometer method or any other
standard method
 0.97 to 1.02

Viscosity Test
 It is fluid property of bitumen
 Measure of resistance to flow
 Influences the strength of resulting mixes
 Very low and high viscosity decreases the
stability of mix
 High viscosity – non homogenous mix
 Low viscosity – no uniform film on aggregates,
just lubricates
 Orifice type viscometer and other types of
equipment is used
 Time noted for receiving specific quantity of bitumen
material through orifice

Flash and Fire point test
 High temperatures – Bitumen leaves
volatiles
 These are inflammable
 Important to know at where it catches fire
 According to BIS, flash point is the
temperature at which the vapour of the
bitumen momentarily catches fire in the
form of flash.
 Fire point is the temperature at which the
material gets ignited and burns
 Flash point should be min 175C

Water content test
 Bitumen distilled in petroleum
 Heated
 Wait of water condensed and collected
is expressed as the percentage by
weight of original sample
 Allowable maximum water content
should not be more than 0.2% by weight

Loss on Heating Test
 Bitumen loses volatility upon heating and gets
hardened
 50gms of sample is weighed and heated to
163C for 5 hours
 Sample weighed after heating
 Loss in weight is expressed as the percentage
by weight of the original sample.
 For paving mixes not more than 1% is allowed
 How ever, if the bitumen has penetration
values of 150 -200mm 2% is allowed.

Pavement Materials Bitumen

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