Presentation on BITUMEN

By:-suraj - praveen -naraynaabhijeet -bhupalkaushlendra kumar verma

GRADING 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.

Gradation OF Bituminous binders

MELTED BITUMEN

Penetration GradING

Uses penetration results to specify grade

Adds flash point testDuctilitySolubilityThin film oven agingPenetration 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

ADVANTAGESExplains 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

bitumensDoes 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 GRADING

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 mulitplying centistokes by the specific gravity of the asphalt.

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 SystemThe actual tests conducted are as

follows:Viscosity TestSoftening Point  Ductility TestPenetration Index or Penetration RatioMatter Soluble in Organic SolventsRotating 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 BenefitsRheological 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.

• 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.

Consistency: Viscosity-

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 viscometerFundamental 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 fluidThe kinematic viscosity take into account

the inertial forceSI unit = m^2/s

Measurement of kinematic viscosity :

By efflux viscometerStandard 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 = volume/flow………………..seconds

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 flow time and calibration factor gives kinematic viscosity.

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

QUESTIONS IF ANY…??