Bitumen is a black or dark colored solid or viscous substance obtained from fractional distillation of crude oil. It is used in highway construction due to its binding and waterproofing qualities. There are different types of bitumen including cutbacks, emulsions, and modified binders. Cutbacks are made by blending bitumen with solvents to reduce viscosity, while emulsions involve suspending bitumen droplets in water using emulsifiers. Modified binders involve adding polymers to bitumen to improve properties like temperature resistance. Pavements can be flexible, using bituminous materials in layers, or rigid, using a solid concrete slab.

1. UNIT 4
Bitumen, types– cutback, tar, emulsion and modified binders, viscosity
based gradation of bitumen.
Types of Pavements

2. BITUMEN
 Bitumen is a black or dark colored solid or viscous cementitious
substance having an adhesive properties.
 Used in highway construction for their binding and waterproofing
qualities
 It consists chiefly high molecular weight hydrocarbons derived
from fractional distillation of crude oil

3. Crude oil is heated in a furnace
so that hydrocarbons can be
separated via their boiling point.
Inside large towers, heated
petroleum vapors are separated
into fractions according to
weight and boiling point.
The lightest fractions, which
include gasoline, rise to the top
of the tower before they
condense back to liquids.
The heaviest fractions will settle
at the bottom because they
condense early.
Fractional Distillation

4. Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake
Bermudez in Venezuela.
Bitumen also occurs in unconsolidated sandstones known as "oil
sands" in Alberta, Canada

5. Bitumen
obtained by fractional
distillation of crude oil
less temperature
susceptible product
Soluble in carbon
disulphide and in
carbon tetrachloride
Tar
destructive distillation
of coal or wood in the
absence of air.
Tar is a temperature
susceptible product
Its weather resisting
ability is inferior to
bitumen
Soluble in toulene
It has good weather
resisting property

6. Requirements of Bitumen
 The desirable properties of bitumen depend on the mix type and
construction.
 In general, Bitumen should posses following desirable properties.
 The bitumen should not be highly temperature susceptible during the
hottest weather the mix should not become too soft or unstable, and
during cold weather the mix should not become too brittle causing
cracks.
 The viscosity of the bitumen at the time of mixing and compaction
should be adequate. This can be achieved by use of cutbacks or
emulsions of suitable grades or by heating the bitumen and aggregates
prior to mixing.
 There should be adequate affinity and adhesion between the bitumen
and aggregates used in the mix.

7. Modified
Bitumen
Cutbacks
Emulsions
Bitumen is difficult to work with, at ambient temperatures since it is a
highly viscous material under these conditions. it can, however be
transformed into a workable state by blending with petroleum solvents or
by emulsification with a surfactant in water to form a bitumen emulsion.

8. EMULSIONS
 Emulsified Bitumen usually consists of bitumen droplets suspended in water
in the presence of emulsifier.
 Emulsifier – soaps, colloidal powders
 The average diameter of these tiny droplets of bitumen is about 2 micron.
 The bitumen content in the emulsion is around 40-60% and the remaining is
water.

9.  In the 1st step water is mixed with appropriate emulsifying agent and other
chemicals.
 The 2nd step is the addition of bitumen with the water-emulsifier mix. This
is done in a colloidal mill. Water-emulsifier mix and bitumen is pumped to a
colloidal mill. The colloidal mill breaks the bitumen into tiny droplets.
 Emulsifier creates a coating of surface charge around the bitumen droplets
that helps to keep these tiny particles away from each other. It also helps to
keep these particles in a dispersed form.
EMULSIONS - PRODUCTION
Ref:http://www.pmgsy.nic.in/cationic.pdf

10.  When bitumen emulsions are applied on aggregates, water starts to evaporate causing separation
of bitumen from water. And then bitumen spreads on the surface of the aggregate and acts as a
binding material and slowly attains its strength.
 Depending upon the speed at which water evaporates and bitumen particles separate from water
EMULSIONS
• bitumen is intended to break rapidly. Therefore this type of emulsion sets and
cures rapidly. SURFACE DRESSING
Rapid Setting Emulsion (RS)
• the process of breaking starts when fine dusts of minerals are mixed with
aggregate-emulsion mix. PREMIX WITH AGGREGATE, PATCHING
Medium Setting Emulsion (MS)
• manufactured by using special type of emulsifier, which makes the setting
process very slow. These types of emulsion are relatively stable. RAINY
SEASON
Slow Setting Emulsion (SS)

11. Ref:http://www.pmgsy.nic.in/cationic.pdf

12.  Advantages of Bitumen Emulsions
 It can be used in damp environment on wet aggregates
 Road repair work can be carried out in minimum time
 It can be used in any season
 Since heating is not required it cant pollute air
 Long storage stability in clean containers/Tanks
 Choice of viscosity for different applications.
EMULSIONS

13.  Cutback bitumen is obtained by blending bitumen with suitable volatile diluents or
solvents to lower the viscosity of the bitumen to desired range.
 The distillates used for preparation of cutback bitumen are naphtha, kerosene,
diesel oil, and furnace oil.
 Consists of 80 % bitumen and 20 % solvent
 Cutback bitumen is used for cold weather bituminous road construction and
maintenance. No heating is required
 After the cutback mix is used in the construction work, the solvent from the
bituminous material will evaporate and the bitumen will bind the aggregate.
CUTBACKS

14. Rapid Curing
(RC)
• Bitumen + light diluent of high viscosity(naptha)
• recommended for surface dressing and patchwork.
Medium
Curing (MC)
• Bitumen + medium diluent of intermediate
viscosity(kerosene)
• recommended for premix with less quantity of fine aggregates.
Slow Curing
(SC)
• Bitumen + low viscosity diluent (diesel)
•used for premix with appreciable quantity of fine aggregates.
There are different types of cutback depending on the rate at which the
diluent evaporates and cutback hardens

15.  Modified Bitumen have binders whose properties have been modified by the
use of a modifying agent which when added to the original bitumen alters its
chemical structure and/or physical and mechanical properties in order to make it
more resistant to temperature variations, weather and high traffic loads.
 More stable under heavy loads, braking and accelerating forces and shows
increased resistance to permanent deformation in hot weather.
 It resists fatigue loads and having better adhesion between aggregates and
binders.
 Types of Modifiers :
MODIFIED BINDERS
Sulphur
Crumb Rubber from discarded tyres
Styrene-butadiene-Styrene (SBS)
Ethylene vinyl acetate (EVA),polypropylene,

16.  Commonly used modifying agents are polymers. depending upon the nature of
the polymer, these modifiers can be classified as:
 Plastomers: EVA(Ethylene Vinyl Acetate) , EBA(Ethylene Butyl Acrylate),
ETP(Ethylene Ter Polymer) etc.
 Elastomers: SBS(Styrene-Butadiene Styrene), SIS(Styrene isoprene Styrene).
 Advantages of using PMB:
 reduce the temperature susceptibility of the bitumen binder and bitumen mix
 Better adhesion of the binder to the aggregate
 Water resistance properties are increased
 Resistance to fatigue and rutting
POLYMER MODIFIED BITUMEN

17. Application of PMB:
 On Heavy traffic levels, curves, crossroads etc.
 Where there is risk of high and low road surface temperatures
 For heavy duty applications
 To improve durability in remote areas
 In high rainfall areas and high stress conditions
POLYMER MODIFIED BITUMEN

18. In India, until recently grading was done on the basis of Penetration
PG 30/40,60/70, 80/100.
Viscosity graded system has recently been adopted in India for
paving bitumen based on IS 73:2006 Paving Bitumen – Specification
(Third Revision) issued in July 2006.
Viscosity Grade bitumen is designed to take care of lowest
temperature(responsible for cracking) and maximum
temperature(responsible for rutting).
Viscosity is measured at 60 degree C and 135 degree C, which takes care of
both low and high temperature susceptibility of the binder, which is not
possible with penetration value at 25 degree C.
.
Viscosity Grade Bitumen

19. Viscosity Grade Bitumen

20. Types of Pavements

21. Flexible Pavements
 Flexible pavements are constructed using bituminous materials.
 Less flexural strength
 Flexible pavements will transmit wheel load stresses to the lower layers by
grain-to-grain transfer through the points of contact in the granular
structure.
 Flexible pavement layers reflect the deformation of the lower layers on to
the surface layer (e.g., if there is any undulation in sub-grade then it will be
transferred to the surface layer).

22. Flexible pavement may be constructed in a number of layers and the top
layer has to be of best quality to sustain maximum compressive stress, in
addition to wear and tear. The lower layers will experience lesser magnitude
of stress and low quality material can be used.
The wheel load acting on the pavement will be distributed to a wider area,
and the stress decreases with the depth
.
Flexible Pavements

23.  Rigid pavements have sufficient flexural
strength to transmit the wheel load stresses
to a wider area below.
 Compared to flexible pavement, rigid
pavements are placed either directly on the
prepared sub-grade or on a single layer
of granular or stabilized material.
 Rigid pavements are constructed by
Portland cement concrete (PCC) and
should be analyzed by plate theory instead
of layer theory, assuming an elastic plate
resting on viscous foundation.
Rigid pavements