Module 1.pdf

Pavement Materials and Construction (PM&C) Module 1
Abhinag, Assistant Professor, CED, AIT, Chikkamagaluru Page | 1
MODULE 1
Syllabus
AGGREGATES: Origin, classification, requirements, properties and tests on road
aggregates, concepts of size and gradation – design gradation, maximum aggregate size,
aggregate blending to meet specification.
BITUMEN AND TAR: Origin, preparation, properties and chemical constitution of
bituminous road binders; requirements
AGGREGATES
Aggregates form the major portion of pavement structure and they form the prime materials
used in pavement construction.
Aggregates are mainly used in-
 Granular Bases and Sub-Bases
 Bituminous Courses
 Cement Concrete Pavements
Origin
Aggregates are obtained from two important sources. They are,
 Natural aggregates
These are the aggregates which are evolved from the natural process of breakdown of
rocks that is obtained from the nature in pure form.
In simple words, natural aggregates are obtained from rock
 Artificial aggregates
Manmade aggregates or the waste slags from industries form strong hard material,
which can be effectively used as aggregates for the pavement construction important
artificial aggregates are
- Broken brick ballast
- Slag
Natural Aggregates
a. Igneous rocks
Cooling of molten material
b. Sedimentary rocks
Deposition of granular material
c. Metamorphic rocks
Transformation due to heat & pressure
a. Igneous rocks
Predominantly crystalline and are formed by the cooling of molten rock magma.
Common Igneous rocks used are,
• Granite
• Basalt
Some key features of these rocks are,
- Hard and durable
- Resistant to abrasion
- Low absorption of water
- Fine grained to coarse grained texture
Very good for bituminous courses and cement concrete pavements

Further igneous rocks are classified as below:
Classification based on grain size:
a) Course (>2mm)
b) Medium (2mm to 0.2mm)
c) Fine (<0.2mm)
Classification based on composition:
a) Acid rocks (>66% silica, light in colour & specific gravity <2.75)
b) Intermediate rocks (55 to 66% silica)
c) Basic rocks (<55% silica, dark in colour & specific gravity >2.75)
b. Sedimentary rocks
Formed either from the deposition of insoluble granular material resulting from the
disintegration of pre-existing rocks, or form the inorganic remains of marine and animals
which are deposited in great quantities on the sea floor. Sedimentary rocks are deposited
in layers; they have stratified or laminated structure.
Commonly used Sedimentary rocks are,
• Limestone
• Sandstone
- Reasonably hard and durable
- Liable to a smooth polish
- Fine grained
- High absorption of water
Good for sub-base and base courses
Classification based on predominating mineral:
a) Calcareous rock (chalk, lime stone & dolomite)
b) Siliceous rock (sand stone, flint & chert)
c) Argillaceous (clay & shale)
c. Metamorphic rock
These are sedimentary or igneous rocks that have been subjected to great heat or to great
pressure or both, that has resulted in the formation of minerals and in textures different
from those of the original rock.
Commonly used metamorphic rocks are,
• Quartzite
- Reasonably hard and durable
- Resistant to abrasion
- Low absorption of water
- Fine grained to medium grained texture
Good for base courses, bituminous courses and cement concrete pavements

Classification based on grain size:
a) Fine grain size (Hornfels & Schist)
b) Coarse grain size (Gneiss & Granulite)
Requirements:
Following are the important requirements of road aggregates that are to be noted before
using for the road construction.
o They must be crushed aggregate.
o They shall be clean, hard, durable and cubical in shape.
o They must be free from dust, organic matter.
o They should not be Flakey or Elongated.
o They must not consist of injurious or harmful materials such that they reduce the
strength of structure.
o They should resist wear and tear due to abrasive action of traffic loads
Properties of Aggregates
The road aggregates should possess the following important properties since they should
serve for long duration
a. Strength
b. Hardness
c. Toughness
d. Durability
e. Shape
f. Adhesion with bitumen
1) Strength
1. The aggregates to be used in road construction should be sufficiently strong to
withstand the stresses due to traffic wheel loads.
2. The aggregates which are to be used in top layer of the pavements, particularly in the
wearing course have to be capable of withstanding high stresses in addition to wear and
tear; hence they should possess sufficient strength and resistance to crushing.
2) Hardness
1. The aggregates used in the surface course are subjected to constant rubbing or abrasion due
to moving traffic.
2. They should be hard enough to resist the wear due to abrasive action of traffic.
3. Abrasive action may be increased due to the presence of abrasive material like sand
between the tyres of moving vehicles and the aggregates exposed at the top surface.
4. This action may be severe in the case of steel tyred vehicles.
5. Heavy wheel loads can also cause deformations on some types of pavement resulting in
relative movement of aggregates and rubbing of aggregates with each other within the
pavement layer.

6. The mutual rubbing of stones is called attrition, which also may cause a little wear in the
aggregates; however attrition will be negligible or absent in most of the pavement layers.
3) Toughness
1. Aggregates in the pavements are also subjected to impact due to moving wheel loads.
2. Severe impact like hammering is quite common when heavily loaded steel tyred vehicles
move on water bound macadam roads where stones protrude out especially after the
monsoons.
3. Jumping of the steel tyred wheels from one stone to another at different levels causes
severe impact on the stones.
4) Durability
1. The stone used in the pavement construction should be durable and should resist
disintegration due to the action of weather.
2. The property of the stones to withstand the adverse action of weather may be called
soundness.
3. The aggregates are subjected to the physical and chemical action of rain and ground water,
the impurities there-in and that of atmosphere.
4. Hence it is desirable that the road stones used in the construction should be sound enough
to withstand the weathering action.
5) Shape of aggregates
1) The size of the aggregates is first qualified by the size of square sieve opening through
which an aggregate may pass, and not by shape.
2) Aggregates which happen to fall in a particular size range may have rounded, cubical,
angular flaky or elongated shape of particles.
3) It is evident that the flaky and elongated particles will have less strength and durability
when compared with cubical, angular or rounded particles of the same stone.
4) Hence too flaky and too much elongated aggregates should be avoided as far as possible.
5) The voids present in a compacted mix of coarse aggregates depend on the shape factors.
6) Adhesion with Bitumen
The aggregates used in bituminous pavements should have less affinity with water when
compared with bituminous material; otherwise the bituminous coating on the aggregates will
be stripped off in presence of water.

Tests on Road Aggregates
Code of Practice for Tests
1. Aggregate Crushing Test
Aim: To determine the crushing value of the given sample of aggregate.
Apparatus
a) Steel cylinder with open ends and a square plate
b) Plunger with piston
c) Cylindrical measure
d) Weighing balance
e) IS sieves (12.5 mm, 10.0mm & 2.36 mm)
f) Compression testing machine
g) Steel Tamping Rod.
Procedure:
1. Select clean and dry aggregate passing through IS 12.5 mm and retained on IS 10.0
mm sieve.
2. Weight the empty cylindrical measure. Let the weight be ‘a’ g

3. Fill the aggregate in the cylindrical measure in three layers, tamping each layer 25
times with the rounded end of the tamping rod. Weigh the cylindrical measure with
aggregate. Let the weight be ‘b’ grams. Thus the weight of aggregate = W1 g
4. Transfer the aggregate into the steel cylinder again in three layers tamping each
layer 25 times
5. Place the plunger in the steel cylinder such that the piston rests horizontally over
the aggregate surface.
6. Keep the assembly of steel cylinder with plunger in the compression testing
machine.
7. Set the pointer to read zero and apply the compressive load of 40 tonnes.
8. Stop the machine. Take out the assembly.
9. Sieve the crushed material on IS 2.36 mm sieve and find the weight of material
passing this sieve. Let the weight be W2 g.
10. Then Aggregate crushing value=W2 / W1*100 %
Tabular Column
Weight of empty cylindrical measure = ‘a’ g
Weight of cylindrical measure with aggregate = ‘b’ g
Weight of aggregate taken in the cylinder before test =(b-a) = W1 g
Weight of crushed material Passing IS 2.36 mm sieve = W2 g
Aggregate crushing value = W2 / W1* 100 %
Result
The Aggregate Crushing Value (ACV) of the given aggregate Sample is ______
Desirable Values
Layer Max. ACV (%)
Surface Course 30
Other Surfaces 45
2. Los Angeles Abrasion Test
Aim: To determine the abrasion of the given aggregate sample.
Apparatus:
a) Los Angles Abrasion Machine
b) Steel Charges (Depending on the Grade selected)
c) Weighing balance
d) IS Sieves (Depending on the Grade Selected)
Procedure
1. Take the clean and dried aggregates in an oven at 105-110° C.
2. Based on the selected grade of aggregates, sieve them through respective sieves and mark
upto the standard weight mentioned for each grade and record its weight as W1
3. Put these aggregates along with the corresponding steel charges in the Los Angeles
Abrasion testing machine
4. Turn on the machine and allow it to rotate for 500 revolutions with 333-35rpm
5. After completing said rotations, stop the machine and take out the fraction of aggregates
and sieve it through 1.7 mm IS sieve.
6. Record the weight of aggregate fraction retained on the sieve (W2)

7. Aggregate Abrasion Value=(w2/w1)*100 %
Result
Aggregate Abrasion Value (AAV) of the given sample =______
Desirable Value
Layer Max. AAV (%)
GSB-Sub Base Course 60
WBM- Base Course 50
BM-Wearing/Binder Course 40
BC-Surface Course 30
3. Aggregate Impact Test
Aim: To determine the impact value of the given aggregate
Apparatus:
a) Aggregate impact apparatus
b) IS sieves (12.5 mm, 10.0 mm and 2.36 mm)
c) Cylindrical measure and cylindrical cup
d) Weighing balance.
e) Tamping rod.
Procedure
1. Take clean and dry aggregate and sieve on IS 12.5 mm and 10.00 mm sieve.
2. Collect the aggregate passing IS 12.5mm sieve and retained on IS 10.0 mm Sieve.
3. Find the weight of empty cylindrical measure. Let the weight be ‘a’ g.
4. Fill the aggregate in the cylindrical measure in three layers, tamping each layer 25
times with the rounded end of the tamping rod.
5. Roll the tamping rod over aggregate surface and remove excess aggregate, if any.
6. Find the weight of the cylindrical measure with aggregate. Let the weight be ‘b’ g.
Thus the weight of aggregate = W1 = ( b-a )
7. Transfer all the aggregate from the cylindrical measure to the test cylinder in one layer
and tamp the layer 25 times with the rounded end of the tamping rod.
8. Fix the test cylinder firmly to the base of the impact tester.
9. Adjust the height of fall of the plunger to 380+ 5mm and set the blow counter to zero.
10. Lift the plunger gently and allow it to drop. This is one blow. Give 15 such blows.
11. Take out the test cylinder and sieve the crushed material on IS 2.36 mm sieve. Find
the weight of material passing the sieve. Let weight be W2 g.
12. Then, Aggregate Impact Value (AIV) = W2 / W1 * 100 %
Tabular Column
Weight of empty cylindrical measure = ‘a’ g
Weight of cylindrical measure with aggregate = ‘b’ g
Weight of aggregate taken in the cylinder before test =(b-a) = W1 g
Weight of crushed material Passing IS 2.36 mm sieve = W2 g
Aggregate Impact Value = W2 / W1* 100 %

Result
Aggregate Impact Value (AIV) of the given sample =______
Desirable Value
Layer Max. AIV (%)
WBM- Base Course 45
4. Shape Test
Aim
To determine the Flakiness Index, Elongation Index and Angularity Number of the given
sample of aggregate
1. Flakiness Index
The Flakiness index of aggregate is the percentage by weight of particles whose least
dimension [thickness] is less than three- fifths [0.6] times of their mean dimension. The
test is not applicable to aggregate size smaller than 6.3 mm
Apparatus
a) Thickness gauge
b) Weighing balance
c) IS Sieves of sizes
63 mm, 50 mm, 40 mm, 31.5 mm,25 mm,20 mm, 16 mm, 12.5 mm, 10 mm and 6.3 mm
Procedure
1. The sieves are arranged such that the largest size sieve (63 mm) is at the top and the
smallest size sieve (6.3 mm) is at the bottom.
2. The given aggregate are sieved. A minimum of 200 pieces of each fraction to be tested
are taken and weighed = W1 g.
3. In order to separate flaky aggregate, each fraction is then gauged for thickness through
the respective opening on the thickness gauge. For example, if the aggregate is from 50 –
40 fraction, it is gauged through the opening of 27.00 mm on the thickness gauge.
4. The flaky aggregate passing the respective openings are collected and accurately
weighed = w1 g.
5. The procedure is repeated for other fractions having weights W2, W3, etc. and the
flaky aggregate in them having weights w2, w3 respectively are weighed.
6. Then,
(w1+w2+w3+------)
Flakiness Index = ---------------------------- x 100
(W1+W2+W3+-------)
Result
The flakiness Index of the given sample of aggregate is __________
2. Elongation Index
The elongation index of an aggregate is the percentage by weight of particles whose greatest
dimension (length) is greater than one and four fifth times [1. 8] times their mean dimension.
The elongation test is not applicable to size smaller than 6.3 mm.

Apparatus
a) Length gauge
b) Weighing balance
c) IS Sieve of size as in flakiness Index test
Procedure
1. The sample is sieved through the IS sieves specified and a minimum of 200 pieces of each
fraction are taken and weighed = W1 g.
2. In order to separate elongated aggregate , each fraction is then gauged individually for
length through the respective opening on the length gauge
3. In each fraction, the aggregate retained on the respective opening on the length gauge is
collected and weighed =X1 g.
4. The procedure is repeated for other fractions having weights W2, W3, etc, and the weights
of elongated aggregate in them X2, X 3 etc, are found.
5. Then
(X1+X2+X3 +----------------)
Elongation Index = _____________________________ x 100 %
(W1+W2+W3+----------------)
Result
The elongation Index of the given sample of aggregate = __________ %
Tabular Column
9 10 6.3 W9= 4.89 w9 14.7 X7
Total ---- W = ---- w = ---- X =

The Combined Flakiness and Elongation Index =FI+EI=________%
3. Angularity Number
The angularity number of an aggregate is the amount by which the percentage voids exceeds
33, after being compacted in a prescribed manner. The angularity number is found from the
expression (67 - 100 * W / CG, percent). Here the value 67 represents the percentage volume
of solids of most rounded gravel, which would have 33 percent voids
Apparatus
a) A metal cylinder closed at one end having 3 litre capacity, diameter and height
approximately equal
b) A metal tamping rod, 16 mm in diameter and 600 mm long.
c) Weighing balance
d) IS sieves 25, 20, 16, 12.5, 10, 6.3 and 4.75 mm
Procedure
1) The sieves for each fraction (as specified) are arranged such as 25 - 20 mm, etc.
2) The given sample of aggregate is sieved so that sufficient pieces are obtained in each
fraction.
3) The empty cylinder is accurately weighed = ‘ a’ g
4) Each aggregate fraction is separately filled in the cylinder in 3 (three) layers tamping each
layer 100 (hundred) times with the rounded end of tamping rod. The excess aggregate are
removed.
5) The cylinder along with aggregate is weights = ‘b’ g
6) The aggregate are removed from the cylinder. The cylinder is completely filled with water
and after wiping its outer sides it is weighed with water = ‘d’ g
7) Then Angularity number may be calculated from the expression,
Angularity number = 67 - 100 W / CG
Where, W= Mean weight of aggregate in the cylinder
C = Weight of water required to fill the cylinder
G= Average Specific gravity of aggregate
Result
The angularity number of the given sample of aggregate = …………. %
Observations
Desirable value
Layer Max. Combined FI&EI (%)
WBM- Base Course 15
*Also the Angularity Number should be less than or equal to 11%

5. Specific Gravity and Water Absorption Test
*(Quality & Porosity properties of road aggregates are evaluated in this test)
Aim
To determine the specific gravity and water absorption of given sample of aggregates.
Apparatus
a) Density basket
b) Weighing balance
c) Water tank
d) Tray
e) IS sieves- 10mm and 20mm
Theory
The specific gravity of an aggregate is considered to be a measure of strength or
quality of the material. Stones having low specific gravity are generally weaker than those
with higher specific gravity values. The specific gravity test helps in the identification of
stone.
Water absorption gives an idea of strength of rock stones having more water
absorption are more porous in nature and are generally considered unsuitable unless they are
found to be acceptable based on strength, impact and hardness.
Procedure
1) Take about 2kg of given aggregates passing IS 20mm sieve and retained on 10mm sieve.
2) Keep the aggregate in density basket and then keep the basket in water.
3) Allow the aggregate and basket to be in water for 24 hours.
4) After 24 hours find the suspended weight of basket with aggregate.
5) Remove the basket out of water and remove the aggregate.
6) Keep the empty basket back in water and find the suspended weight.
7) Wipe the surface of aggregate using a cotton cloth to make them surface dry.
8) Find the weight of surface dry aggregate in air.
9) Keep the aggregate in oven at 110° C for 24 hours.
10) Now find the weight of dried aggregate in air.
11) Find both the values using standard formula mentioned below in the table
Observation

Result
The specific gravity of given aggregate sample = ………………….
The water absorption of given aggregate sample = ………………...%
Desirable Value
Specific gravity should be between 2.5 to 3. An average value of 2.68 is highly desirable
Water absorption should be between 0- 2$. Rare cases of 4% can also be seen and admissible.
6. Soundness Test
Aim
To study the resistance of aggregates to weathering action, by conducting accelerated
weathering test cycle
Apparatus
a) Sodium sulphate or magnesium sulphate
b) Oven
c) Weighing balance
d) IS sieves
Procedure
1) In order, to quicken the effects of weathering due to alternate wet-dry or freeze-thaw
cycles in the laboratory, the resistance to disintegration of aggregate is determined by using
saturated solution of sodium sulphate or magnesium sulphate.
2) Clean, dry aggregates of specified size is weighed and counted. Then immersed in the
saturated solution of sodium sulphate or magnesium sulphate for 16 to 18 hours.
3) Then the aggregates are dried in an oven at 105-110°C to a constant weight, thus making
one cycle of immersion and drying.
4) The number of such cycles is decided by prior agreement and then the specimens are
tested. After completing the final cycle, the sample is dried and each fraction of aggregate is
examined visually to see if there is any evidence of excessive splitting, crumbling or
disintegration of the grains.
5) Sieve analysis is carried out to note the variation in gradation from original. The coarse
aggregate fraction of each size range is sieved on specified sieve sizes.
Desirable value
IRC has specified 12percent as the maximum permissible loss in soundness test after 5 cycles
with sodium sulphate, for the aggregate to be used in bituminous surface dressing,
penetration macadam and bituminous macadam constructions.
7. Bitumen Adhesion/Stripping Test
Several laboratory tests have been developed to determine the adhesion of bituminous binder
to an aggregate in presence of water. These tests may be classified into six types:
a) Static immersion test
b) Dynamic immersion test
c) Chemical immersion test
d) Immersion mechanical test
e) Immersion trafficking test and
f) Coating test

The static immersion test is very commonly used as it is quite easy and simple. The principle
of this type of test is by immersing aggregate fully coated with the binder in water maintained
at specified temperature and by estimating the degree of stripping. The result is reported as
the percentage of stone surface that is stripped off after the specified time periods.
Desirable value
IRC has specified the maximum stripping value as 25 percent for aggregate to be used in
bituminous construction like surface dressing, penetration macadam, bituminous macadam
and carpet.
Hydrophilic and Hydrophobic Aggregates
Most of the road stones have surfaces that are electrically charged. Silica, a common
constituent of igneous rocks posses a weak negative charge and hence these have greater
attraction with the polar liquid water than with bituminous binders having little polar activity.
These aggregates which are electronegative are water-linking and are hydrophilic.
Basic aggregates like lime-stones have a dislike for water and greater attraction to bitumen,
as they have positive surface charge. These aggregates are called hydrophobic.
Type of charge of aggregates used in road plays a vital role in bituminous construction.
Bitumen is also available as cationic or positive and anionic or negative and hence a suitable
selection may be made depending on aggregates available. Cationic (+) bitumen may be
selected for electronegative aggregate and anionic (-) bitumen for electropositive aggregates.
Concepts of Size and Gradation
The gradation analysis or sieve analysis of weight the coarse and the fine aggregates available
is carried out by sieving through the standard IS sieves.
Dry sieve analysis is generally used when aggregates contain fine slit or clay sticking to a
coarser particle used sieve analysis is carried out.
Design Gradation
It is the gradation or distribution of particles or aggregates specified by the designer. The
design gradation is obtained using a number of trials by mixing different size aggregate to
satisfy the requirement of density and CBR value.
Maximum Aggregate Size
Maximum aggregate size is the sieve size or mean size of the smallest sieve through which
100% of material will pass.
Aggregate Blending
Aggregate blending is a method of mixing the aggregates of different sizes to obtain or to
satisfy the design gradation. There are several techniques used to blend the aggregates. The
trial method is the one in which the aggregates are blended by several trials to get the design
gradation and to meet the required specification.

Two graphical methods in common use for proportioning/blending are:
1) Triangular Chart
2) Rothfutch’s Method
The Rothfutch’s Method is highly preferred over triangular chart method because the
Rothfutch’s method is very simple and, many numbers of mixes can be obtained from this.
Rothfuch’s Method
This method is used when a number of materials have to be mixed together for obtaining a
desired or design gradation.
On a graph paper, with Y-axis representing percentage passing and X-axis representing
particle size as shown in figure. A diagonal line is drawn from point corresponding to (100
percent passing, maximum particle size of the material) to a point corresponding to (zero
percent passing, smallest particle size of the materials)
For different materials say A, B and C, sieve analysis has to be done and percentage finer has
to be calculated for each range of particle size for all the materials and grain size distribution
curves of these three materials are plotted as shown in fig and the balancing straight lines of
A, B and C are obtained
The opposite ends of the balancing straight lines of A and B are joined (i.e., zero percent
passing of materials A is joined with 100 percent passing of B). Similarly the opposite ends
of balancing lines of B and C are joined.
The points where these lines meet the desired gradation line represent the proportion in which
the materials A, B and C are to be mixed. These values may be read from the Y-axis by
projecting the points of intersection as shown in fig.

Module 1- Part B
Bitumen and Tar: Origin, preparation, properties and chemical constitution of bituminous
road binders; requirements
Introduction
Bituminous binders used in pavement construction works include both bitumen and tar. Both
bitumen and tar have similar appearance, black in colour though they have different
characteristics.
Origin
Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic
algae and other once-living things. When these organisms died, their remains were deposited
in the mud on the bottom of the ocean or lake where they lived. Under the heat and pressure
of burial deep in the earth, the remains were transformed into materials such as bitumen,
kerogen, or petroleum. Deposits at the La Brea Tar Pitsare an example. There are structural
similarities between bitumens and the organic matter in carbonaceous meteorites.
Asphalt or bitumen can sometimes be confused with "tar", which is a similar black,
thermoplastic material produced by the destructive distillation of coal. During the early and
mid20th century when town gas was produced, tar was a readily available product and
extensively used as the binder for road aggregates. The addition of tar to macadam roads led
to the word tarmac, which is now used in common parlance to refer to road-making materials.
However, since the 1970s, when natural gas succeeded town gas, asphalt (bitumen) has
completely overtaken the use of tar in these applications.
BITUMEN
It is a petroleum product obtained by the distillation of petroleum crude.
TAR
It is a thermoplastic material obtained from the destructive distillation.
Difference between Bitumen and Tar

Different forms of bitumen
Cutback bitumen
Normal practice is to heat Bitumen to reduce its viscosity. In some situations preference is
given to use liquid binders such as cutback bitumen. In cutback bitumen Suitable solvent is
used to lower the viscosity of the bitumen. From the environmental point of view also
cutback bitumen is preferred. The solvent from the bituminous material will evaporate and
the bitumen will bind the aggregate. Cutback bitumen is used for cold weather Bituminous
road construction and Maintenance. The distillates used For preparation of cutback bitumen
are naphtha, kerosene, diesel, oil and furnace oil. There are different types of cutback
bitumen Like rapid curing(RC),medium curing(MC), And slow curing(SC).RC is
recommended for Surface dressing and patchwork. MC is recommended For premix With
less quantity of fine aggregates.SC is used For premix with appreciable quantity of fine
aggregates.
Bitumen Emulsion
Bitumen emulsion is a liquid product in which bitumen is suspended in a finely divided
condition in an aqueous medium and stabilized by suitable material. Normally cationic type
emulsions are used in India. The bitumen content in the emulsion is around 60% and the
remaining is water. When the emulsion is applied on the road it breaks down resulting in
release of water and the mix starts to set. The time of setting depends upon the grade of
bitumen. The viscosity of bituminous emulsions can be measured as per IS:8887-
1995.Threetypes of bituminous emulsions are available, which are Rapid
setting(RS),Medium setting (MS),And Slow setting (SC).Bitumen Emulsions are ideal
binders for hill road construction. Where Heating of bitumen or aggregates are difficult.
Rapid Setting emulsions are used for surface dressing work. Medium Setting emulsions are
preferred for premix jobs and patch repairs work. Slow setting Emulsions are preferred in
rainy season.
Bituminous Primers
In bituminous primer the distillate is absorbed by the road surface on which it is spread. The
absorption there for depends on the porosity of the surface. Bitumen primers are used full on
the stabilized surfaces and water bound macadam base courses. Bituminous primers are
generally prepared on road sites by mixing penetration bitumen with petroleum distillate.
Modified Bitumen
Certain additives or blend of additives called as bitumen modifiers can improve properties of
Bitumen and bituminous mixes. Bitumen treated with these modifiers is known as modified
bitumen. Polymer Modified Bitumen (PMB)/Crumb Rubber Modified Bitumen (CRMB)
should be used only in wearing course depending upon the requirements of extreme climatic
variations. The detailed specifications for modified bitumen have been issued by IRC: SP:
53-1999. It must be noted that the performance of PMB and CRMB is dependent on strict
Control on Temperature during construction.
Preparation of Road Bitumen from Petroleum
The refining of petroleum is most complex procedure producing a tremendous range of
products from the simplest hydrocarbon gas methane to the hardest bitumen with constituents
of molecular weight of the order of several thousands.

The preparation of different forms of bitumen for road purposes from petroleum is illustrated
in the above figure.
Fig. 1 Preparation of Road Bitumen
a) Distillation of Petroleum
Bitumen is produced from selected crude oils by a process of concentration by distillation.
The distillate is obtained in the desired boiling point ranges by condensation in a fractionating
column.
It is first to heat the crude oil to a temperature lower than 350°C under atmospheric pressure
to drive off light fractions such as gasoline, kerosene and gas oil.
Further heating above 400°C is necessary to drive off heavier oils.
Refining of the topped crude is carried out by use of reduced pressures and steam injection in
the fractionating column.
The incoming crude is pumped through a continuous pipe-still similar to that used in tar-
distillation plants, where it is raised to desired temperature (between 200 and 400° C)
It is then injected into a fractionating column where at the reduced pressure volatile
components flash into vapours.
The vapours are condensed into fractions of decreasing boiling point by condensation at
points at higher levels in the fractionating column.
A flow diagram representing the distillation of topped oil in a modern refinery is given in
figure below:

Fig. 2: Bitumen Production
b) Air-Rectification of Refinery Bitumen
Bitumen produced by straight steam-refining from crude oils may be deficient in the
components of high molecular weight which are insoluble in heptanes, asphaltenes fractions.
It is common practice to increase the asphaltene content by oxidation of the hot straight-run
bitumen by a current of air blown through it.
These are bitumen of high softening point produced by an oxidation by air-blowing at high
temperatures.
The oxidation is more extensive and the blown bitumens have rubbery qualities required for
certain industrial purposes and not used as binders for road aggregates.
Chemical Constitution of Bitumen
Bitumen although formed from distillation process causes some changes which is closely
related in chemical nature to its primary source i.e., the crude petroleum oil.
Bitumen is completely soluble in carbon-di-sulphide but most of them divide the bitumen
soluble in carbon-di-sulphide into 3 fractions:
a) Carbenes: fraction insoluble in carbon tetrachloride.
b) Asphaltenes: fraction insoluble in light aliphatic hydrocarbon solvent such as petroleum
ether.
c) Maltenes: fraction soluble in light aliphatic hydrocarbon solvent
The molecular weight of asphaltene fraction is estimated between 1800 and 1,40,000 and
maltenes have molecular weight between 370 and 710.
The hydrocarbons in petroleum are of four basic forms:
a) Saturated aliphatic groups or paraffins
b) Naphthenic groups or cycloparaffins
c) Aromatic ring compounds
d) Aliphatic groups with olefin double bonds
Aliphatic group normally does not present in road bitumen. The approximate proportions of
the other three groups in the molten groups can be obtained from modified Waterman
analysis

Many properties of bitumen, particularly the non-Newtonian flow properties suggest that
bitumen is a colloidal system. The colloidal nature of bitumen is due to the presence of
asphaltenes in association with high molecular weight material from the maltenes fraction,
form a disperse phase. This complex is normally referred as ‘micellar phase’.
On the basis of flow properties, bitumen can be divided into two types, ‘sol’ type, in which
there is little interaction between micelles or a ‘gel’ type in which interaction of micelles
aregreat enough to cause a loose structure formation. Most of the distilled road bitumens are
sol type, blowing leads to gel type structures.
Requirements of Bitumen
The desirable properties of bitumen depend on the mix type and construction.
a) Mixing: type of materials used, construction method, temperature during mixing, etc.
b) Attainment of desired stability of the mix
c) To maintain the stability under adverse weather conditions
d) To maintain sufficient flexibility and thus avoid cracking of bituminous surface and
e) To have sufficient adhesion with the aggregates in the mix in presence of water
Desirable Properties of Bitumen
1) Viscosity
The viscosity of the bitumen at the time of mixing and compaction should be adequate. This
is achieved by heating the bitumen and aggregate prior to mixing or by use of cutbacks or
emulsions of suitable grade.
2) Temperature Susceptibility
The bituminous material should not be highly temperature susceptible. During the hottest
weather of the region the bituminous mix should not become too soft or unstable. During cold
weather the mix should not become too hard and brittle, causing cracking. The material
should be durable.
3) Adhesion Property
In presence of water the bitumen should not strip off from the aggregate. There has to be
adequate affinity and adhesion between the bitumen and aggregate used in the mix.
Tests on Bitumen
There are a number of tests to assess the properties of bituminous materials. The following
tests are usually conducted to evaluate different properties of bituminous materials.
1. Penetration test
2. Softening point test
3. Ductility test
4. Viscosity test
5. Specific gravity test
6. Heat stability test
a. Flash point test
b. Fire point test
c. Loss on heating test
7. Solubility test
8. Thin film oven test

9. Float test
10. Water content test
1. Penetration Test
An indirect method of measuring viscosity is the measure of penetration of a standard needle
under standard conditions of load, time & temperature. The test measures the hardness or
softness of bitumen in terms of penetration expressed in mm/10th of std needle.
Temperature= 25o
C [test to be performed after sample is kept for 1hr in H2O bath at this
temperature]
Load on needle = 100 g
Time in which penetration is recorded = 5 s
The penetration is measured by a graduated dial.
Bitumen is softens to a poring consistency a depth more than 15mm in the container is
poured. The expected penetration sample is cooled in 60 min in air and 60 min in water
before testing. The standard needle is positioned to get a penetration value for 5sec and is
noted.
The penetration value obtained is represented in 80-100 or 80/100 grade bitumen at standard
consistence and it range from 20-225mm.
In cold region bitumen with High penetration value is used.
In warm region low penetration value is used ex. 30/40 grade.
The factors which affect the Penetration test is test temperature, needle size and weight and
period of cooling.
2.Softening Point Test
The softening point is the temperature at which the substance attains a particular degree of
softening under specified condition of test. A viscosity material like bitumen or tar doesn’t
have a well defined softening point. However a std test determines the temperature at which a
std ball will pass through a disc of bitumen contained in ring. The test is known as ring & ball
test.
A brass ring of internal dia 17.5 mm at top and 15.9 mm at bottom and of depth 6.4mm.The
steel ball of 9.5mm dia and 2.5g. Support distance is 25mm between the bottom of the ring
and top surface of the bottom plate of support is provided. Glass container of 85mm dia and
120mm depth is used. The bitumen is heated to poring consistency and poured into ring and
cooled for half an hour before testing. A brass ring containing the bitumen sample is
suspended in H2O or glycerin at given temperature a steel ball is placed on the disc of
bitumen. The liquid medium is then heated at a rate of 50
C increase per minute. Metal plate
placed at a specified bituminous material touches the bottom at the softening point. With
increase in temperature bitumen melts and come down with the weight of ball at particular
temperature it touches the bottom plate that point temperature is noted.
The softening point is range between 35 to 750
C.

The liquid water is used for bitumen having softening point less than 800
C and Glycerine is
for softening point more than 800
C.
Higher softening point indicates lower temp. susceptibility and in warm climet.
The factors which affect the softening points are quality and type of liquid used, weight of
ball, distance between bottom of the ring and bottom base plate and rate of temperature.
3. Ductility test
In flexible pavement construction it is important that the binders form ductile thin film
around the aggregate. This serves as a satisfactory binder in improving the physical
interlocking of the aggregate bitumen mixes. Under traffic loads the bitumen layer is
subjected to repeated deformation and recoveries. The binder material which does not possess
sufficient ductility would crack and thus provide pervious pavement surface. The test is
believed to measure the adhesive property of bitumen and its ability to stretch. The ductility
of a binder is an indication of its elasticity & ability to deform under load & return to original
condition upon removal of the load. A material which doesn’t possess adequate ductility
would crack under a load.
This is unsatisfactory since water can penetrate into the surfacing through there cracks. The
property is determined by measuring the distance that a std briquette of bitumen, necked to a
cross section of 1 sq-cm will stretch without breaking when elongated at a rate of 5 cm/min at
270
C. The ductility values should be a minimum of 50 as per IS.
The briquette mould is filled with bitumen and cool for 30 min in air and 30 min in water
before testing. Then it is fixed to expanding machine assembly which stretches the bitumen at
a rate of 5cm/min and expands till to break and the point is noted by scale.
The factors which affect the ductility is pouring and test temperature, dimension of briquette
mould, rate of pulling and period of cooling.
4. Viscosity Test
Viscosity is the property of a fluid that determines the resistance offered by the fluid to a
shearing force under laminar flow conditions, it is thus the opposite of fluidity.

The determination of viscosity is generally done by efflux viscometers. They work on
common principles, though they differ in detail. The liquid under test is poured to a specified
level into a container surround by water or oil bath providing temperature control at the base
of the container is a small orifice with a simple valve control on opening valve, the time in
seconds is recorded for a stated quantity of liquid to discharge into a measuring liquid below.
The different type of viscosity testing operator is there they are Efflux viscometer, Standard
tar viscometer (10mm dia orifice and 50ml fluid to discharge), Saybolt furol viscometer
(3mm dia orifice and 60ml fluid to discharge).
The bitumen is placed in to a standard tar viscometer or efflux viscometer and its temperature
is raised to test temperature specified (35, 40, 45, 55& 600
C). When the temperature reaches
respective test temperature orifice valve is open time elapse is noted to collect the bitumen of
50ml. The time required to collect a bottom container of 50ml is five indirectly the viscosity
of bitumen. Then is specified in VG 10, VG20, VG 30 and VG 40.
5. Specific gravity test
In most applications bitumen is weighed, but finally in use with aggregate the bitumen
content is converted on volume basis. Hence determine of specific gravity value is required
for conversion of weight to volume. Specific gravity of a binder doesn’t influence its
behavior but all the same, its value is needed for mix design.
Specific gravity of bitumen varies from 0.97 to 1.02.
Specific gravity of tar varies from 1.16 to 1.28.
There are two methods to test the specific gravity of bitumen
a. Pycnometer method
b. Balance method
Generally balance method is used in that a cup of 50ml capacity is used and it is oiled before
using. The bitumen is poured in to cup and cooled and its weight e is noted and weight of
cupwith bitumen when immersed in distilled water is weighed f. Specific gravity of bitumen
is the ratio of e to the difference between (e and f).
It is used to convert the weight in to volume. Determines Purity of bitumen if the impurity
present in the bitumen by showing high value of specific gravity
6. Heat stability test:
When a bituminous binder is heated continuously it starts emitting volatile vapors above a
certain temperature and these volatile vapors can momentarily catch fire in form of flash and
continued heating get fired.

a. Flash point:
The flash point of bitumen is that temperature at which it gives off vapors, which ignites in
the pressure of a flame, but don’t continue to burn. The flame point is an induction of critical
temperature at & above which suitable precautions should be taken to eliminate fire hazards.
The ISI test describes the Penske-Martin method. The method involves a cup into which the
bitumen is filled. The bitumen sample is then heated at a rate of 5-60C/min stirring the
material continuously.
The test flame is applied at intervals. The flash point is taken at the temperature read on the
thermometer when flame causes a bright flash in the interior of cup in a closed system & at
the surface of material in open system. It is 2200c.
b. Fire point test:
If heating is continued beyond the flash point, the vapors ignite in the pressure of a flame &
continue to burn indicating the fire point temperature. There is no standard method to
determine the spontaneous ignition temperature, which can only broadly indicate.
c. Loss on heating test:
The effect of heat on a bituminous binder is the loss of volatile constituents. This loss causes
the binder to harden. Thus one method of testing the desirable property of a binder is to find
out the loss on heating. This is achieved by an accelerated heating test a 50gm sample is
weight is taken and maintained at a temperature of 1600
c for 5hours. Then it expressed as a
percentage of loss in original weight is determined.
Tar
Tar is the viscous liquid obtained when natural organic materials such as wood and coal
carbonized or destructively distilled in the absence of air. Based on the materials from which
tar is derived, it is referred to as wood tar or coal tar. It is more widely used for road work
because it is superior.
There are five grades of roads tar: RT-1, RT-2, RT-3, RT-4 and RT-5, based on their
viscosity and other properties.
 RT-1 has the lowest viscosity and is used for surface painting under exceptionally
cold weather as this has very low viscosity.
 RT-2 is recommended for standard surface painting under normal Indian climatic
conditions.
 RT-3 may be used for surface painting, renewal coats and premixing chips for top
course and light carpets.
 RT-4 is generally used for premixing tar macadam in base course.
 RT-5 is adopted for grouting purposes, which has highest viscosity among the road
tars.
The various tests carried out on road tars are:
a) Specific gravity test
b) Viscosity test on standard tar viscometer
c) Equiviscous temperature (EVT)
d) Softening point
e) Softening point of residue
f) Float test

g) Water content
h) Phenols, percent by volume
Preparation of Tar
There are three stages in the production of road tar:
1) Carbonization of coal to produce crude tar
2) Refining or distillation of crude tar
3) Blending of distillation residue with distillate oil fractions to give the desired road tar.
a) High-Temperature Carbonization of Coal
The carbonization or destructive distillation of coal consists essentially of heating a thin
layer of coal enclosed in a chamber of refractory brick-work for several hours at
temperature about 1000° C. Majority there are two major methods for carbonization, they
are:
a) Carbonization in Coke-ovens
b) Carbonization in gas-works retorts
Carbonization in Coke-Ovens
A batch of about 16 tons of coal is loaded into a coke-oven.
Coke oven consists of large thin box lined with brick, 40 feet long, 14 feet high and 1 ½
feet wide.
The charge of coal is heated for 18 hours at a temperature of 1200° C.
Each ton of coal yields 8 gallons of crude tar.
b) Distillation of Crude Tar
The crude tar obtained by the condensation of the vapours emitted from coal in the course
of carbonization is subjected to distillation process.
c) Blending of Tar-Distillation Fractions to Produce Road Tar
It is evident from the above that a tar of a suitable viscosity for use on the roads could be
left as residue simply by stopping the distillation at the appropriate point.

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