Grading of bitumen by SURAJ KUMAR

Presentation on BITUMEN
By:-
suraj - praveen -narayna
abhijeet -bhupal
kaushlendra kumar verma

Gradation OF Bituminous binders
• Penetration grading : on the basis of
penetration at 25*C.
• Viscosity grading : on the basis of viscosity
at 60*C.
• Performance grading : graded by the
conditions (s. temperatures) at the binder is
expected to perform satisfactorily.

Uses penetration results to specify
grade
Adds
 flash point test
Ductility
Solubility
Thin film oven aging
Penetration
Ductility

Penetration Grade
Grade penetration
S35 30/40
S45 40/50
S55 50/60
S65 60/70
S90 80/100
S200 175/225
S stands for straight run bitumen (not
blended neither modified nor blown)

Penetration Grade
Bitumen 80/100: The characteristics of this grade
confirm to that of S 90 grade of IS-73-1992.
 This is the softest of all grades available in
India.
This is suitable for low volume roads and is still
widely used in the country. (less than
1500cvpd)
Even used in High altitude/snow bound regions

Bitumen 60/70:
 This grade is harder than 80/100 and can withstand
higher traffic loads.(greater than 1500cvpd)
 The characteristics of this grade confirm to that of
S 65 grade of IS-73-1992.
 It is presently used mainly in construction of
Expressways National Highways & State
Highways.
Can withstand heavier axle loads.

Bitumen 30/40
 This is the hardest of all the grades and can
withstand very heavy traffic loads.
 The characteristics of this grade confirm to that of
S 35 grade of IS-73-1992.
 Bitumen 30/40 is used in specialized applications
like airport runways and also in very heavy traffic
volume roads in coastal cities in the country.
 Suited for areas where difference in min. and
max. temperature is 25*C.

Specifications for S65 bitumen (IS73-1992)
characteristic requirement
Specific gravity at 27*C Min .99
Water (%) by mass Max .2
Flash point Min 175*C
Softening point 45-55*C
Penetration at 25*C 100g 5s 60-70
Penetration ratio PEN (4*C 200g 60s/25*C
100g 5s)*100
Min 35
Durability at 27*C MIN 75cm
Paraffin wax content (%) Max 4.5
Fraass breaking point Min -6*C
Loss on heating TFO Test Max 1%
Retained penetration after TFO Min 52% of original
Matter soluble in tricholoroethylene Min 99%
Viscosity @ 60*C Poise 2000+/-400
@135*C cSt Min 300

ADVANTAGES
Explains well near average in service temperature
Fast n can be used in field labs
Low cost of equipment, simplicity and short testing
times needed to obtain results.
Temperature susceptibility can be determined (I
wont agree)
material properties at the average in service
temperature (I.e the average between summer highs
and winter lows)

Disadvantages
Simple but empirical (not fundamental)
Cannot be used for grading polymer modified
bitumens
 Does not provide guidance regarding mixing
and compaction temperatures to be used for
bituminous mixes (viscosity at high
temperatures is not available)
Penetration grading specifications do not
provide a good idea about the temperature
susceptibility of the binder.
 It does not tell much about the rheological
behavior of bitumen.

PROBLEM WITH PENETRATION
GRADING SYSTEM

 Viscosity is shear stress divided by the shear strain rate.
 These units of measurement provide at least a limited
estimate of fundamental material properties.
 The easiest way to picture shear is to visualize a deck of
cards which have a vertical line marked on the side.
 As pressure is applied to the top of the deck, the cards
slide over one another and the marked dots on the
individual cards start to separate.
 The shear rate is the rate at which these dots separate.

Two viscosity measurements are used in this
specification:
Absolute viscosity (60 oC) and kinematic viscosity
(135 oC).
 Both use the principle of the rate of flow through
a known area to measure viscosity.
Because asphalt is still very thick (stiff) at 60 oC,
a vacuum is needed to move the asphalt through
the tube in a reasonable time.
 At 135 oC, gravity and a falling head pressure is
sufficient to get the asphalt to flow.

At the 60 oC test temperature, the tube is charged
at 135 oC and then placed in the test temperature
bath.
The tube temperature is allowed to equalize with
the bath temperature, a vacuum line is attached
to the top of the small diameter tube, and the
flow is started.
 The time it takes the asphalt to flow past the
timing marks times the tube calibration constant
gives the viscosity of the asphalt in Poise.

The tube is charged in the 135 oC bath and left
for about 20 minutes.
 A vacuum line is touched briefly to the top of
the small diameter tube until the asphalt moves
over the upper hump in the tube.
 The time it takes the asphalt to flow past the
timing marks times the tube calibration
constant gives the viscosity of the asphalt in
centistoke.
Centistokes are converted to centipoise by

Requirements on both the absolute and kinematic
viscosities are set in these specifications. The
grading system is based on the absolute viscosity
(60 oC).
A minimum viscosity at 135 oC is included to help
define the maximum rate of change of material
properties with temperature.
A minimum penetration value is also included in
these specifications as a means limiting
temperature susceptibility.

 The penetration values decreases with increasing
viscosity.
 In other words, the stiffer the asphalt, the less distance
the needle will penetrate into the asphalt.
 As with the penetration specifications, requirements for
safety and limits on aging of the binder during
construction are included. The flash point temperature
requirements increase with increasing viscosity (less
volatiles with increasing viscosity).
 Maximum limits on viscosity after thin film oven aging
limit the amount of acceptable aging during mixing and
construction.

TABLE 2 EXPLANATION
The minimum requirements for the 135 oC viscosity
and penetrations are increased. There is also an
increase in the required ductility after aging for the
harder (higher viscosity) asphalts.

Neither Table 1 or Table 2 specifications place any
lower limit on the rate of change in properties with
temperature. This means that the pavement
performance of a given AC 20 can still vary widely.

Information from this testing can be used to
estimate appropriate mixing and compaction
temperatures.
This is accomplished by graphing viscosity in Poise
(on a log scale of the y-axis) versus temperature
(arithmetic scale on the x-axis).
The mixing temperature is selected so that an equal
viscosity is achieved. Based on historical
experience, a viscosity of 1.7 + 0.2 Poise is used.
The temperature at which the viscosity is 2.8 + 0.3 is
used to select the compaction temperature.

viscosity GradING
INTRODUCTION to viscosity grade
 In this third revision grading of Bitumen is
changed from penetration grade to viscosity grade.
 To improve the quality of Bitumen, BIS revised
IS-73-1992 Specifications based on viscosity
grade (viscosity @ 60 deg. C) in July 2006. As per
the Specifications ,there are four grades VG-10,
VG-20, VG-30 & VG-40.

With the current revision several key
issues are addressed, like:
Performance
Issues
Adoption

advantages of viscosity grade
Based on the fundamental Engineering
Takes care of low as well high temperature
. Any two same Viscosity Grade Bitumen
would give similar rutting performance in hot
summer unlike Penetration Grade.

Greater Mix in ease design
Less no. of tests save time and cost
longer Durability
Takes higher Traffic

Viscosity Based System
The actual tests conducted are as follows:
Viscosity Test
Softening Point
 Ductility Test
Penetration Index or Penetration Ratio
Matter Soluble in Organic Solvents
Rotating Thin Film Oven Test (RTFOT)
Specific gravity of bitumen

Performance grading
• Also called as the superpave (superior performance
pavements) performance gradation
• Binders are graded by the temperature range (high and
low) within which the binder has appropriate properties to
perform satisfactorily
 Against rutting mode of failure (high service temp.)
 Against fatigue failure of bituminous mixes (inter. Temp)
average service temperature
 Against low temperature cracking (low temperatures)

• Engineering principles involved in
addresses bitumen pavement problems.
• Tests & specifications are applicable for
unmodified and modified binders.

• The physical properties measured as per this
method are directly related to the performance of
the binder in terms of engineering principles and
not by experience.
• Specifications are available for long term aged
bitumens also
• Here in this gradation we are normally not
talking about penetration. Complex system and
costly equipments used.This is considered to be
very rational

• Complete range of temperatures experienced at a
given site are considered for selecting an appropriate
grade of bitumen for the site
• Example: PG 58-12 represents a binder that is
expected to perform satisfactorily in a region having
7-day max. pavement temperature of 58*C and Min.
pavement temperature of -12*C.

Rheology of bitumen
Science of Flow
 Mostly we are interested in resistance to
flow - But without rupture - Depends on
dealing with strain/stress
Relaxation and recovery are important

Uses and Benefits
Rheological measurements of fundamental
material properties. This is comparable across
systems
These can be related to actual performance of
both binders and mixes and their composition .
Instrument based so can be used for precise
reproducible measurements
Can use real world variables and effects like
healing

viscosity
 Fundamental rheological property of bitumen
 Rheology is the study of flow and deformation of materials
 Viscosity is the “resistance offered by the fuild to a
shearing force” (opposite of fluidity)
 It is necessary to learn about the flow and deformation of
bituminous binders at different temperatures
(corresponding to construction and service).
 Viscosity at high handling temperatures (135*C or 150*C)
and high (60*C) or low service temperature.

Consistency: Viscosity-
• Following figure illustrates typical temperature-viscosity relationships for asphalts
• Grades of asphalt materials and
temperatures at which they are used
depend to a great extent on their viscosity
• Plant temperatures for mixing asphalt-paving
materials are usually specified in
terms of viscosity
• Temperature limits corresponding to
viscosities of 1.5 to 3.0 cm2/s (150 to 300
centistokes) are sometimes used
For example, the plant temperatures for
heating the asphalts A, B, and C (as
shown in the figure) will respectively be in
the following ranges corresponding to
viscosities of 150 to 300 centistokes: 153
ºC to 167 ºC; 148 to 163 ºC; and 137 ºC to
149 ºC.

1 Dynamic or absolute viscosity :
The force (tangential force) required to
move the upper plate with constant velocity
is proportional to area of bitumen film
(binder), velocity but inversely proportional
to thickness of film.

F= n (Av/d)
n = (Fd/Av)
n = t/(v/d)
Ns/m^2

Measurement of absolute viscosity
A]sliding plate viscometer
Fundamental definition as principle : Bitumen
film of known thickness is sandwiched between
two parallel plates.
Test conducted at selected temperature ,selected
rate of shear (v)
Force required to move the plate at a velocity of v
is measured.

B. rotational viscometer
• Overview
 The Rotational Viscometer (RV) used to
determine the viscosity of asphalt binders in
the high temperature range of
manufacturing and construction.
This measurement is used in the Superpave
PG asphalt binder specification

• The RV test helps ensure that the asphalt binder is
sufficiently fluid for pumping and mixing .
• The basic RV test measures the torque required to
maintain a constant rotational speed (20 RPM) of
a cylindrical spindle while submerged in an
asphalt binder at a constant temperature. This
torque is then converted to a viscosity and
displayed automatically by the RV.
• The standard Rotational Viscometer procedure is
found in:AASHTO T 316 and ASTM D 4402:
Viscosity Determination of Asphalt Binder Using
Rotational Viscometer.

KINEMATIC viscosity :
The ratio of viscous force to inertial force.
Kinematic viscosity = dynamic
viscosity/density of fluid
The kinematic viscosity take into account
the inertial force
SI unit = m^2/s

Measurement of kinematic viscosity :
By efflux viscometer
Standard size of orifice : time for
standard volume of flow is measured at
the given test temperature.
Unit : seconds (instruments are
calibrated to obtain the corresponding
kinematic viscosity)
Kinemtic viscosity =

common efflux viscometer :
 standard tar viscometer (for viscosity
of tar)
 sybolt furol viscometer (viscosity of
bitumen, emulsion)
 Engler viscometer

Capillary Viscometers :
 kinematic viscosity obtained by
observing the time required for a fixed
volume of fuild to flow through a
standard capillary tube.
 Narrow glass tubes (having narrow
and wide sections through which
bitumen flows)
Two or more marks on the tube to
indicate a particular volume of flow.
Viscometers calibrated and product of

 Time required for fuild to flow from one
mark to other obtained and
corresponding calibration factors are
available from the manufacturer
depending on the size of capillary tube
and arrangement and bulb we have.
 Temperature bath (maintained)
 Water or with or without vaccum.

References
• HP Bitumen Handbook
• Internet Sources
• Highway construction by kadyali

Grading of bitumen by SURAJ KUMAR

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