Bitumen and

modified bitumen

bitumen tar

Natural

Straight run bitumen

coal

Blown bit

wood

Cut back

Emulsion Modified bitumen

Rapid curing

Medium curing

Slow curing

cationic

anionic

CRMB

NRMB

PMB

artificial

Rocks

lakes

Bituminous material

BITUMEN• Bitumen is defined as a viscous liquid , or a

solid consisting essentially of hydrocarbons and their derivatives, which is soluble in carbon disulphate.

TAR• Obtained by destructive distillation of coal or

wood.• Tar contain more free carbon which is insoluble

in carbon trichloroethylene.• They are also readily distinguished by odour.

Natural bitumen• Naturally occurring Bituminous binder• Lake bitumen: They are found in depression in

earth’s surface which have accumulated in lakes.

• Rock bitumen: These are deposits of limestone or sandstone naturally impregnated with bitumen.

Artificial Bitumen Straight run bitumen

• When the residue is distilled to a definite consistency without further treatment, the distillation is known as “straight running” and the residue, is teamed as “straight-run-bitumen”.

Blown bitumen

• Blown bitumen is a bitumen obtained by further treatment of straight run bitumen by running it, while hot, into a vertical column and blowing air through it.

Cut back• Cut back is defined as bitumen whose viscosity

has been reduced by the addition of a volatile diluents.

• Depending upon the diluent used, there are three types of cut-backs.

• Rapid curing: Bitumen which has been fluxed with a naphtha type of distillate.

• Medium curing: Bitumen which has been fluxed with a kerosene type of distillate

• Slow curing: A liquid residue produced in the refining process, containing little or no volatile constituents.

Emulsion• Emulsion is relatively stable dispersion of a

liquid, subdivided in another liquid in which it is not soluble.

• Emulsion of bitumen =bitumen+ emulsifier/additives + water

• Free flowing dark brown liquid• Emulsions of bitumen can be of two type: 1.Anionic - bitumen particle has negative

charge 2. Cationic - bitumen particle has positive

charge

Properties of bitumen1.They contain predominantly hydrocarbons, with small

quantities of sulphur, oxygen, nitrogen and metals. 2.They are predominantly soluble in carbon disulphide

(CS2) the portion insoluble in CS2 being generally less than 0.1 %.

3.Most bitumens are colloidal in nature. 4.Bitumens are thermoplastic, i.e. they soften on

heating and harden on cooling. 5.They have no specific melting point, boiling point or

freezing point, though a form of softening point is used in their characterization.

6.Bitumens are insoluble in water.

7.They are highly impermeable to the passage of water.

8.They are generally hydrophobic(water-repellent), but may be made hydrophilic(water liking) by the addition of small quantity of surface active agents.

9.They are chemically inert.10.They oxidize slowly.

Advantage of Bitumen

They are more tolerant. They can be used in relatively cold weather. They are ideal for patching and repair work. They are useful for sealing cracks.

Tests on bitumen

• Consistency test 1. penetration test 2. viscosity test 3. softening point test 4. float test

• Ductility test• Flash and fire point test• Specific gravity test• Distillation test• Water content test• Solubility test

Consistency tests:

• Consistency defined as the resistance of a material to flow.

• Since this property changes as the temperature varies, it must be realized that there is no single method of the test that can readily evaluate all bituminous binders for consistency over such a wide range

Penetration test• To determine the penetration grade of bitumen to

be used for road construction. • It gives the choice to select the grade of bitumen

according to the climate condition of the area where the road is to be constructed.

• Consistency of a bituminous material expressed as the distance 1/10th of mm that a standard needle vertically penetrates a sample under standard conditions of load, time and temperature.

• Standard test condition: emperature : 25°C Load on needle : 100 grams Time in which penetration are recorded : 05 seconds

Procedure : • Temperature raised up to 100°C above its

softening point. • Sample is cooled to a temperature of 5°C. • Place the sample in the penetrometer. • Standard needle is approximately 50mm in length

and 1.00 to 1.02mm in diameter. • At least three penetration are carried out, then

the nearest whole value unit the average of the three penetration, whose values do not differ maximum by 8, gives the penetration value of the bitumen.

Viscosity test• The viscosity of a liquid is the property that retards flow so

that when a force is applied to a liquid; the slower the movement of the liquid, the higher the viscosity in this sense viscosity is the pure measure of consistency.

• Procedure: • Time is measured in seconds for a fixed quantity of the

binder liquid to flow from a cup through a standard orifice under an initial standard head and at a known test temperature.

• The temperature ranges from 25°-100°C and generally so selected that the specific viscosity is no more than 45poise

• The orifice having size of 10mm is used for important physical characteristic of road.

Softening point test • Softening point is not a melting point; bituminous binders do

not melt but instead gradually changes from semi solids to liquids when heated.

• Ring and ball test: • Procedure: • A steel ball 3/8 inch dia weighing (3.5 +- 0.03) gms, is placed

upon a disk of sample contained.• The liquid medium is then heated at the rate of 5°C increase

per minute.• The temperature at which the softened bituminous material

touches the bottom metal plate placed at a specified distance below the ring is recorded as the softening point.

Float test • For the certain range of consistency of the

bitumen materials, orifice viscometer test or penetration test can’t be used to define consistency of material.

• Float test measures the material of this group.

Procedure: • A float made of aluminium and a brass collar is

filled with the specimen material to be tested. • Test specimen is cooled to room temp for 15-60

min at 5°C and screwed in to the float.

• The float assembly is then placed in a water bath at 50°C and the time required in seconds for water to force its way through the bitumen plug is noted, as the float test value.

• Higher the float test value stiffer is the material.

Ductility test

• The ductility of binder is an indication of its elasticity and ability to deform under load and return to original condition upon removal of load

Procedure: • The distance to which it will elongated before breaking when two ends of a briquette are pulled at a specified temp (25°C) and speed is measured. • Minimum cross section of the briquette before

testing is 1sq.cm.

Flash and fire point

• Flash point: The flash point of a material is the lowest temperature at which the vapour of a substance momentarily takes fire in the form of flash under specified test condition.

• Fire point: the fire point is the lowest temperature at which the material gets ignited and burns under specified test condition.

Procedure:• The bitumen is filled in the cup upto a filling

marks and bitumen sample is heated at the rate of 5°C to 6°C per minute, stirring the material.

• The test flame is applied at the intervals.• the flash point is taken as the temperature

read on the thermometer.• If heating is continued beyond the flash point

vapours ignite in the presence of a flame and continues to burn, indicating the fire point temperature.

Specific gravity test• Sp gravity is defined as the ratio of the weight of

given volume of material at a given temp to that of an equal volume of water at the same temp.

Procedure:• Take clean and dry sp. Gravity bottle and weigh along

with the stopper(weight ‘A’)• Fill the sp. gr. Bottle with distilled water and keep in

water bath having a temperature of 27°C+1°C for not less then half an hour and weigh it(weight ’B’)

• Weigh the sp. Gr. Bottle about half filled with the material(weight ‘C’)

• Weigh the sp.gr. Bottle about half filled with the material and other half with distilled water(weight ‘D’) Weigh the sp.gr. Bottle completely filled with the material. (weight ‘E’)

Specific gravity

Distillation test• It is used to find out the quantity and quality of

volatile constituents. • The amount of non volatile residues presents in

road tars, cut back bitumen and binder emulsions.

Procedure: • Two hundred millilitres of the sample is distilled in

a 500ml flask at the a controlled rate to a temp of 360°C for 15 minutes.

• Then determined the volume of distillate removed at prescribed standard temp.

Water content test

• This test is carried out to know the content of water in a sample of bitumen.

• Procedure:• The specimen of known weight is mixed in a pure

petroleum distillate free from water.• It is then heated and the water is distilled off.• The condensed water is collected and its weight is

recorded.• The water content of the specimen is expressed as the

percentage of the weight of condensed water to the weight of the original sample.

• The maximum water in the bitumen should not exceed 0.2 percent by weight.

Solubility testProcedure: • Different solvents are used in determining the

percentage of the binder present in bitumen or tar.

• In the case of bitumen the accepted solvent is carbon disulphide.

• A specified quantity of binder usually about 2gms is dissolved in a given quantity of solvent.

• Filter the solution through a fine porosity filter. • Then the residue retained is determined and the percentage of soluble material is calculated.

Modified bitumen

• A heavy roofing material employing multiple layers of asphalt and reinforcers around a core of plastic or rubber modifiers

Guidelines on use of Modified Bitumen

• MORTH letter No. RW/NH-34041/36/90-S&R(Vol. II) dated April 21, 1999 advised all States/UTs to use Modified Bitumen upto 10% for all works “as it has been proved by field trials that the life of the road increases by 1.5 times”.

• IRC released new Specifications vide publication No. IRC-SP:53:2002 FOR USE OF MODIFIED BITUMEN in road development activities in India.

• MORTH vide letter No. RW/NH-34041/36/90-S&R(Vol. II) dated 17, January 2000 requested all States to start using MODIFIED BITUMEN.

• MORTH letter No. RW/NH-34041/36/90-S&R(Vol. II) dated April 14, 2000 requested MOP&NG to start Modified Bitumen production at Refinery level.

Guidelines on use of Modified Bitumen

• MORTH vide their letter No. RW/NH-35072/1/2001-S&R( R ) dated June 21, 2001 has requested all States to encourage use of Modified Bitumen in view of its various advantages and improved performance over conventional Bitumen.

• MORTH vide their letter No. RW/NH-33041/3/2001-S&R dated June 13, 2002 has stated that “It has been decided that keeping in view its advantages, polymer/rubber modified bitumen may be adopted in surfacing for the whole length, subject to availability”.

Advantage of modified bitumen

• Lower susceptibility to daily and seasonal temperature variation.

• Higher resistance to deformation at high pavement temperature.

• Better age resistance properties.• Higher fatigue life for mixes.• Better adhesion between aggregate and

binder.• Prevention of cracking and reflective cracking.

Crumb rubber• Crumb rubber is a recycled rubber produced from

automotive and truck scrap tires.

Crumb rubber modified bitumen

Bitumen+

Additives (Modifiers/Treated Crumb Rubber)

What is Crumb Rubber Modified Bitumen?

• Crumb Rubber Modified Bitumen is Conventional Bitumen with treated Crumb Rubber Additive at high temperature which results in• Lower susceptibility to temp. variation• Higher resistance to deformation at high temperature• Better Age Resistance Properties• Higher Fatigue Life of Mixes• Better Adhesion Properties

Grades of CRMB

• CRMB is manufactured in three grades for differing weathering conditions.

• Grade 50 is used for colder climates when minimum modification is sufficient.

• Grade 55 is used in moderate climatic conditions where moderate modification is required.

• Grade 60 is used in hot conditions where high modification is required to withstand the extra heat.

characteristic CRMB-50 CRMB-55 CRMB-60

Penetration at 25°c,0.1mm,100g,5sec

<70 <60 <50

Softening point, c(R&B),minimum

50 55 60

Elastic recoveryAt 15°c,%, minimum

50 50 50

Flash point ,°C, min 220 220 220Separation,Difference in softening point,(R&B),°c, maximum

4 4 4

Viscosity at 150°C,Poise 1-3 2-6 3-9Test on residue 1. Penetration at 25 c, 0.1mm,100g,5sec Minimum % of original

60 60 60

2. Increasing in softening point, (R&B),°c, maximum

7 6 5

3. Elastic recovery 25°c,minimum

35 35 35

Natural rubber• Natural rubber also called India rubber, as

initially produced, consist of polymers of the organic compound isoprene, with minor impurities of other organic compounds plus water.

Natural rubber modified bitumen

• Natural rubber modified bitumen is used for prolongation of life of state roads.

• The need to adopt rubber for the use of construction of the roads mainly that it reduces the cost of construction and also recycled rubber is used as it minimize the environment pollution.

Polymer modified bitumen

• Polymer modified bitumen material bring benefits in terms of better and longer lasting roads and saving in total road life costing.

• The main polymer used to modify bitumen are:1. Natural rubber2. Styrene-butadiene-styrene(SBS)3. Ethylene-vinyl acetate (EVA)

General Requirements of Modifiers:

• Be compatible with bitumen. • Resist degradation of bitumen at mixing temperature. • Be capable of being processed by conventional

mixing and laying machinery. • Produce coating viscosity at application temperature. • Maintain premium properties during storage,

application and in service. • Be cost-effective on a Life-cycle-cost basis.

Type of modifier examplesSynthetic Polymers

Plastomeric Thermoplastics

Polyethylene (PE). Ethylene Vinyl Acetate (EVA). Ethylene Butyl Acrylate and Ethylene Tar Polymer (ETP), etc.

Elastomeric Thermoplastics

Styrene Isoprene Styrene (SIS), Styrene-Butadiene-Styrene (SBS) block copolymer, etc.

Synthetic Rubbers

Synthetic Rubber Latex

Styrene Butadiene Rubber (SBR) latex and any other suitable synthetic rubber

Other Rubbers

Natural Rubber

Latex or Rubber powder

Crumb Rubber

Crumb Rubber powder from discarded truck tyres further Improved by additives. viz., gilsonite resin.

Choice of Polymer Modified Bitumen:

• Modified bitumens are generally recommended for the roads with heavy traffic and located in extreme climate areas. The selection of the type of modified bitumen will be based on climatic, traffic, performance reports and life cycle cost analysis.

• The selection criteria for grade of modified bitumen shall be based on atmospheric temperature as given in Table below. The softest recommended grades are PMB 120, NRMB 120 and CRMB50, which shall be used for cold climatic areas.

• PMB 70, NRMB 70 and CRMB 55 are used for moderate climate and PMB 40, NRMB 40 and CRMB 60 are used for hot climate areas and heavy traffic conditions. The specific grade shall be chosen on the basis of minimum and maximum atmospheric temperature in the region as indicated in Table below.

Selection Criteria for PMB, NRMB, CRMB based on Atmospheric Temperature

Minimum pavement temperature C°

Maximum Atmospheric Temperature, C°

< 35 35 to 45 > 45

< 10 PMB/NRMB-120 CRMB-50*

PMB/NRMB-70 CRMB-55

PMB/NRMB-70 CRMB-55

-10 to 10

PMB/NRMB-70 CRMB-50

PMB/NRMB-70 CRMB-55

PMB/NRMB-40 CRMB-60

> 10 PMB/NRMB-70 CRMB-55

PMB/NRMB-70 CRMB-55

PMB/NRMB-40 CRMB-60

Advance Test for Bitumen • Rotational Viscometer • Dynamic Shear Rheometer • Rolling Thin-Film Oven• Pressure Aging Vessel• Direct Tension Tester• Bending Beam Rheometer

Rotational Viscometer: • The Rotational Viscometer (RV) is used to determine the

viscosity of asphalt binders in the high temperature range of manufacturing and construction.

Approximate Test Time: • 1.5 hours from sample preparation to final viscosity

reading for one temperature. 2.5 hours for two temperatures.

Basic Procedure: 1. Preheat spindle, sample chamber, and viscometer

environmental chamber to 275°F (135°C). 2. Heat unaged asphalt binder until fluid enough to pour.

Stir the sample, being careful not to entrap air bubbles. 3. Pour appropriate amount of asphalt binder into sample

chamber. The sample size varies according to the selected spindle and equipment manufacturer.

4. Insert sample chamber into RV temperature controller unit and carefully lower spindle into sample.

5. Bring sample to the desired test temperature (typically 275°F (135°C)) within approximately 30 minutes and allow it to equilibrate at test temperature for 10 minutes.

6. Rotate spindle at 20 RPM, making sure the percent torque as indicated by the RV readout remains between 2 and 98 percent.

7. Once the sample has reached temperature and equilibrated, take 3 viscosity readings from RV display, allowing 1 minute between each reading. Viscosity is reported as the average of 3 readings.

Dynamic Shear Rheometer: • The dynamic shear rheometer (DSR) is used to

characterize the viscous and elastic behaviour of asphalt binders at medium to high temperatures.

Approximate Test Time: • 1 to 2 hours depending upon the number of test

temperatures needed.

Basic Procedure: 1.Heat the asphalt binder from which the test

specimens are to be selected until the binder is sufficiently fluid to pour the test specimens.

2. Select the testing temperature according to the asphalt binder grade or testing schedule. Heat the DSR to the test temperature. This preheats the upper and lower plates, which allows the specimen to adhere to them.

3. Place the asphalt binder sample between the test plates.

4. Move the test plates together until the gap between them equals the test gap plus 0.002 inches (0.05 mm).

5. Trim the specimen around the edge of the test plates using a heated trimming tool.

6. Move the test plates together to the desired testing gap. This creates a slight bulge in the asphalt binder specimen’s perimeter.

7.Bring the specimen to the test temperature. Start the test only after the specimen has been at the desired temperature for at least 10 minutes.

8.The DSR software determines a target torque at which to rotate the upper plate based on the material being tested.

9.The DSR conditions the specimen for 10 cycles at a frequency of 10 rad/sec (1.59 Hz).

10.The DSR takes test measurements over the next 10 cycles and then the software reduces the data to produce a value for complex modulus (G*) and phase angle (δ).

Rolling Thin-Film Oven: • The Rolling Thin-Film Oven (RTFO) procedure provides simulated short term aged asphalt binder for physical property testing.

Approximate Test Time: • 3hours from sample preparation to scraping of

final bottle.

Basic Procedure:1.Heat a sample of asphalt binder until it is fluid to

pour. Stir sample to ensure homogeneity and remove air bubbles.

2. If a determination of mass change is desired, label two RTFO bottles and weigh them empty. These are designated as the “mass change” bottles. Record the weights.

3.Pour 1.23 oz (35 g) of asphalt binder into each bottle (Figure 5). Immediately after pouring each bottle, turn the bottles on their side without rotating or twisting and place them on a cooling rack.

4.Allow all bottles to cool 60 to 180 minutes.5.After cooling, weigh the two mass change

bottles again. Record the weights. 6.Place the bottles in the RTFO oven carousel,

close the door, and rotate carousel at 15 RPM for 85 minutes. During this time, maintain the oven temperature at 325°F (163°C) and the airflow into the bottles at 244 in 3/min (4000 ml/min).

7.Remove the bottles one at a time from the carousel, setting the mass change bottles aside. Residue from the remaining bottles should be transferred to a single container. Remove residue from each bottle by first pouring as much material as possible, then scraping the sides of the bottle to remove any remaining residue. There is no standard scraping utensil but at least 90 percent of the asphalt binder should be removed from the bottle. RTFO residue should be tested within 72 hours of aging.

8.After cooling the two mass change bottles for 60 – 180 minutes, weigh them and discard their residue. Record the weights.

Pressure Aging Vessel • The Pressure Aging Vessel (PAV) provides simulated long

term aged asphalt binder for physical property testing. Asphalt binder is exposed to heat and pressure to simulate in-service aging over a 7 to 10 year period.

Approximate Test Time: • 22 hours from sample preparation to end of vacuum

degassing procedure.

Basic Procedure: 1. Heat RTFO aged asphalt binder until fluid enough to

pour. Stir sample and pour 50 g into a preheated thin film oven pan Pour as many pans as needed for intermediate and cold temperature testing (usually 1 – 3 pans will suffice).

2.Place pans in a pan holder and place inside preheated PAV.

3.Seal the PAV and allow it to return to the aging temperature. Aging temperature is based on the climate where the material is expected to be used. For climates where a PG 52 or lower is specified, the PAV is performed at 194°F (90°C). For climates where a PG 58 or higher is specified, the PAV is performed at 212°F (100°C). For desert climates, it is recommended to perform the PAV at 230°F (110°C).

4.Once the PAV has reached the desired temperature, pressurize the PAV to 300 psi (2.07 MPa) and maintained the pressure for 20 hours.

5.At the end of the aging period, gradually release the pressure and remove the pans from the PAV.

6.Place the pans in an oven set at 325°F (163°C) for 15 minutes, then scrape into a single container sized so that the depth of the residue in the container is between 0.55 and 1.57 inches (14 and 40 mm).

7.Place the container in a vacuum oven at 338°F (170°C) and degas the sample for 30 minutes to remove entrapped air. If not degassed, entrapped air bubbles may cause premature breaking in the DTT test.

Direct Tension Tester • The Direct Tension Tester (DTT) test provides a

measure of low temperature stiffness and relaxation properties of asphalt binders.

Approximate Test Time: • About 4 hours including sample preparation time.

Basic Procedure:1.Heat long term aged (PAV) asphalt binder until

fluid to pour. During heating the sample should be covered and occasionally stirred to ensure homogeneity.

2.Pour the heated sample into two DTT molds, making sure to overpour so that there is excess along the top of the mold. This overpouring will ensure enough asphalt binder to completely fill the mold. Sample preparation is critical and is the largest source of test variation.

3.Allow molds to cool for 30 – 60 minutes at room temperature, then trim the top of sample flush with mold using a hot spatula.

4.To demold samples, cool mold in an ice bath or freezer at 23°F ( -5°C) for 5 to 10 minutes; just long enough that the beam can be easily removed from the mold without damaging it.

5.Mount the sample in the loading frame of the DTT. Match the holes on the end tabs of the sample with the loading pins on the load frame.

6.Remove the slack between the sample and the loading pins. Ideally this can be done automatically by the testing apparatus.

7. Start the test when the load reaches 0.45 lb (2 N). Set the strain rate to 3 percent/minute .

8. Test a total of 6 samples as described in steps 1 through 7.

9. Failure identification. Failure of the sample can occur by two means: fracture (breaks apart in 2 pieces) or unrestrained flow without fracture. In the case of fracture, failure strain is defined as the strain at the moment of fracture. in the case of flow without fracture, failure strain is defined as the strain corresponding to the maximum stress observed. The test should not be continued past 10 percent strain; if the sample has not failed by 10 percent strain, record failure strain as “greater than 10 percent”.

10.Failure location. Ideally failure should occur in the gage section (the 18 mm long section of constant cross-sectional area). If failure occurs in the throat section, note and record this occurrence. The location of failure and its repeatability is highly dependent on sample preparation, straightness and proper mounting.

Bending Beam Rheometer • The Bending Beam Rheometer (BBR) test provides a

measure of low temperature stiffness and relaxation properties of asphalt binders.

Approximate Test Time: • 3 hours (from sample preparation to end of test). Basic Procedure: 1. Set the BBR fluid bath to the desired test temperature.

The fluid should be clear at all test temperatures. Suitable fluids are ethanol, methanol and glycol-methanol mixtures. The specific gravity of the fluid should be less than 0.0655 lb/ft3 (1.05 kg/m3) to prevent the asphalt binder beam from floating.

2. Heat long term aged (PAV) asphalt binder until fluid enough to pour. During heating the sample should be covered and occasionally stirred to ensure homogeneity.

3. Stir the heated sample to remove air bubbles and pour into two aluminium BBR moulds, making sure to overpour so that there is excess sample along the top of the mold. This overpouring will ensure enough asphalt binder to completely fill the mold.

4. Allow molds to cool for 45 to 60 minutes at room temperature, then trim the top of sample flush with mold using a hot spatula.

5. To demold samples, cool mold in an ice bath or freezer at -5°C for 5 to 10 minutes; just long enough that the beam can be easily removed from the mold without damaging it.

6. Place beams in the BBR bath at test temperature for 60 minutes to condition them.

7.Place the test beam on the test supports. 8.To ensure that the loading head and the beam

remain in contact for the entire test, manually apply a 0.008 lb (35 mN) contact load for no more than 10 seconds.

9.Activate the automatic testing system. This system does the following: • Apply a (0.22 lb) 980 mN seating load for 1.0 second. • Reduce the seating load to 0.008 lb (35 mN) and

allow the beam to recover for 20 seconds. • Apply the 0.22 lb (980 mN) test load and maintain the

load constant for 240 seconds. During this period, readings of deflection over time are recorded .

10.Remove the test load and end the test. Repeat steps 7 – 10 for the second beam.

References:• L.R. Kadiyali “principles and practices of Highway Engineering “by

Khanna Publishers

• S.G. RANGWALA “Highway engineering” by Charotar Publication House

• Dr. D.K.SHARMA “Principles, Practices and Design of Highway Engineering”

• www.transportation.org

• www.google.com

• www.pavementinteractive.org