testing of asphalt presentation

7/31/2019 Testing of Asphalt Presentation

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Asphalt is a thick brownish or black substance derived from the

same crude oil which produces kerosene, gasoline and vinyl. It is

literally scraped from the bottom of the barrel after all other

petroleum-based products have been refined or

processed. Asphalt is at least 80% carbon, which explains its deep

black color. Bitumen (or asphalt) is primarily used, when mixed with

mineral aggregates, to produce paving materials.


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ASPHALT/BITUMEN


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What is Asphalt Concrete?

Asphalt concrete is a composite material commonly

used in construction projects such as road

surfaces, airports and parking lots. It consistsof asphalt (used as a binder) and

mineral aggregate mixed together, then laid down in

layers and compacted.


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ASPHALT CONCRETE


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TESTS ON ASPHALT/BITUMEN


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TESTS ON ASPHALT/BITUMEN

Why to Perform Tests?

- To gather as much data as possible, which may be

helpful in the construction of Pavements.

- Material properties can be analyzed by performing

various tests on specified samples of the material.


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CONSISTENCY TESTS

Consistency:

The degree of fluidity or viscosity of the bitumen at a

standard temperature. As the viscosity of bitumen

varies according to its temperature, when comparing

grades of bitumen it is essential to carry out the

tests at a standard temperature.


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Penetration Test


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Penetration Test

Penetration Test measures the hardness or softness of bitumen bymeasuring the depth in tenths of a millimeter to which a standardloaded needle will vertically penetrate a sample of the material underknown conditions of loading, time, and temperature. The bitumen issoftened to a pouring consistency, stirred thoroughly and poured intocontainers at a depth at least 15 mm in excess of the expected

penetration. The procedure for the standard test, which is impliedunless other conditions are stated, is for the pressure to be applied toa load of 100 grams for a period of 5 seconds at a temperature of 25degrees celsius. In running the test at least three determinationsshould be made on the surface of the same sample at points not lessthan 10 mm from the side of the container and not less than 10mmapart. It may be noted that penetration value is largely influenced byany inaccuracy with regards to pouring temperature, size of theneedle, weight placed on the needle and the test temperature. A gradeof 40/50 bitumen means the penetration value is in the range 40 to 50at standard test conditions. In hot climates, a lower penetration gradeis preferred.


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Penetration Test

PURPOSE:

To determine the penetration grade of bitumen, to be used for roadconstruction.

It gives the choice to select the grade of bitumen according to the climaticconditions of the area where the road is to be constructed.

SIGNIFICANCE OF THE TEST:

Used to measure the consistency of semi-solid asphalt bitumen so thatthey can be classified into standard grades.

Penetration values lower than 20 have been associated with bad crackingof road surfacing, while cracking rarely occurs when the penetration

exceeds 30.

Surfacing containing penetration-grade bitumen, must be premixed & laidhot.

The higher penetrations are preferred for use in colder climates.


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Penetration Test

STANDARD TEST CONDITIONS:

Temperature : 25 CLoad : 100 gramsTime : 05 seconds

PROCEDURE:

Raise the temperature up to 100 C i.e. above its softening point.

Sample is cooled to a temperature of 5 C.

Place the sample in the Penetrometer.

Standard needle is approximately 50 mm (2 in.) in length and 1.00 to 1.02 mm (0.039 to0.040 in.) in diameter.

The needle tapered at an angle of 8.7 to 9.7 .

At least three penetrations are carried out, then the nearest whole value unit the average ofthe three penetrations, whose values do not differ maximum by 8, gives the penetrationvalue of the bitumen.

For penetration values greater than 200, three different needles should be used.


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Penetration Test


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Viscosity Test

Viscosity denotes the fluid property of bituminous material and it is a measure of

resistance to flow. At the application temperature, this characteristic greatly influences

the strength of resulting paving mixes. Low or high viscosity during compaction or

mixing has been observed to result in lower stability values. At high viscosity, it resists

the compactive effort and thereby resulting mix is heterogeneous, hence low stability

values. And at low viscosity instead of providing a uniform film over aggregates, it will

lubricate the aggregate particles. Orifice type viscometers are used to indirectly find the

viscosity of liquid binders like cutbacks and emulsions. The viscosity expressed in

seconds is the time taken by the 50 ml bitumen material to pass through the orifice of a

cup, under standard test conditions and specified temperature. Viscosity of a cutback

can be measured with either 4.0 mm orifice at 25o C or 10 mm orifice at 25 or 40o C.


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Viscosity Test


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Viscosity Test


If a binder of very low viscosity is used & pre-mixed with theaggregates, it may flow off the stone while en route from themixing plant to the site.

Conversely, if the viscosity is too high, the mixture may beunworkable by the time it reaches the site.

In case of handling, mixing & spraying, the lower the binderviscosity, the better it would be.

In case of the low-viscosity binders, there is less chance ofpipes blocked, mixing and application temperature can bekept lower, aggregates are more easily coated.


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Viscosity TestMEASUREMENT OF VISCOSITY:

Almost 58 instruments are used for measuring VISCOSITY. They may be divided into main threegroups, based on the following principles of operations.

1- The flow of a body through a liquid.2- The flow of a liquid through a tube.3- The rotation of 1 of 2 co-axial cylinders when the space between them

is filled with a liquid.

Most bitumen binder specifications for road works are based on the results obtained with industrialviscometers that utilize the second principle.

The most common test, which is performed in BRITIAN, is the STANDARD TAR VISCOMETER (S.T.V).

PROCEDURE:

Time is measured, in seconds, for a fixed quantity of the binder liquid (50 ml) to flow from a cup through astandard orifice under an initial standard head and at a known test temperature.

The temperature ranges from 25 -100 C and is generally so selected that the specific viscosity is no morethan 45 dynes sec./cm2.

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


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Softening Point Test


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Softening point is not a melting point; bituminous binders do not melt but instead

gradually change from semi-solids to liquids when heated.

It is useful in the classification of certain asphalts and tars and is indicative of the tendency

of the material to flow at elevated temperatures encountered in service.

When two bitumen have same penetration grade (value), the one with the higher softening

point is normally less susceptible to temperature changes.

Practical significance of the test is limited. Therefore specifications of many bituminous

binders for particular purposes are often written without softening point requirements.


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PROCEDURE:

This method is extensively used to evaluate the consistency ofbituminous binders.

A steel ball of 3/8 in. , weighing (3.5 0.03) gms, is placed upon a disk

of sample contained within a horizontal, shouldered, metal ring of

specified dimensions.

The whole assembly is heated in either ethylene glycol (B.P 193 -204 C) or water bath at a uniform rate (5 0.5 C per min).

Temperature is raised until the test sample is soft enough and allowsthe ball to fall through a distance of 2.5 cm.

Temperature at this point is read to the nearest 0.5 C and calledSOFTENINGPOINT.


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Ductility Test

Ductility is the property of bitumen that permits it to undergo great

deformation or elongation. Ductility is defined as the distance in cm, to which

a standard sample or briquette of the material will be elongated without

breaking. Dimension of the briquette thus formed is exactly 1 cm square. The

bitumen sample is heated and poured in the mould assembly placed on aplate. These samples with moulds are cooled in the air and then in water bath

at 27o C temperature. The excess bitumen is cut and the surface is leveled

using a hot knife. Then the mould with assembly containing sample is kept in

water bath of the ductility machine for about 90 minutes. The sides of the

moulds are removed, the clips are hooked on the machine and the machine isoperated. The distance up to the point of breaking of thread is the ductility

value which is reported in cm. The ductility value gets affected by factors

such as pouring temperature, test temperature, rate of pulling etc.


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Ductility Test


The property is desirable in road bitumen in order to overcome the movements induced inthe surfacing by traffic and temperature stresses.

The ductility test is actually the measure of the internal cohesion of bitumen.

Bitumen possessing high ductility are normally cementations and adhere well to

aggregates. Thus bitumen with 100 cm ductility might well be considered a better road-surfacing constituent than with 10 cm ductility, but a binder with a 80-cm ductility is notnecessarily better than a 60 cm one.

Bitumen possessing high ductility are highly susceptible to temperature changes, whilelow ones are not.

The lack of ductility does not necessarily indicate the poor quality; indeed, bitumen of lowsusceptibility and low ductility are highly desirable as crack-fillers in roadways.

The harder grades of bitumen are less ductile than the softer ones.

Ductility test is probably the most controversial of the many empirical tests found in theasphaltic bitumen literature.


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Ductility Test

PROCEDURE:

The distance to which it will elongate before breaking,

when two ends of a briquette are pulled apart at a

specified temperature (25 C) and speed (50mm per min

5%) is measured.

Minimum cross-section of the briquette before testing is

1 cm2.


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Ductility Test


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Ductility Test


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Float Test

Normally the consistency of bituminous material can be measured

either by penetration test or viscosity test. But for certain range of

consistencies, these tests are not applicable and Float test is

used. The apparatus consists of an aluminum oat and a brasscollar filled with bitumen to be tested. The specimen in the mould

is cooled to a temperature of 5oC and screwed in to oat. The total

test assembly is floated in the water bath at 50oC and the time

required for water to pass its way through the specimen plug is

noted in seconds and is expressed as the oat value.


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Float Test

PURPOSE & SIGNIFICANCE:

- For a certain range of consistency of the bitumen

materials, orifice viscometer test or penetration testcannot be used to define consistency of the material.

- Float Test measures the material of this group.


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Float Test

PROCEDURE:

Sample is completely melted at the lowest possibletemperature that will bring it to sufficiently pouring condition.

A float made of aluminum or aluminum alloy (weighing 37.90-

38.10 gms) and a brass collar (weighing 9.60-10.00 gms) is filledwith the specimen material to be tested.

Test specimen is cooled to room temperature for 15-60 min at5 C and screwed in to the float.

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

Higher the float test value, stiffer is the material.


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Flash Point and Fire Point

At high temperatures depending upon the grades of bitumen

materials leave out volatiles. And these volatiles catch fire which

is very hazardous and therefore it is essential to qualify this

temperature for each bitumen grade. BIS defined the ash point as

the temperature at which the vapor of bitumen momentarily

catches fire in the form of ash under specified test conditions. The

fire point is defined as the lowest temperature under specified test

conditions at which the bituminous material gets ignited and

burns.


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PURPOSE & SIGNIFICANCE:

Bituminous materials leave out volatiles at high temperatures. Thequantity of volatile materials depends upon their grades. Thesevolatiles catch fire causing a flash.

This condition is very hazardous and it is therefore essential to qualifythis temperature for each bitumen grade, so that paving engineersmay restrict the mixing and application temperatures.

Flash and Fire Point tests are primarily safety tests, flash point being

the more important since it indicates the maximum temperature up towhich the binder can be safely heated.

Flash Point of most penetration-grade bitumen lies in the range of246 -316 C.


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PROCEDURE:

The test cup is filled with the sample to the filling line, at a temperaturenot exceeding 100 -180 C above softening point.

The temperature of the sample is increased rapidly at first and then at

slow rate as the flash point is approached.

At specified intervals, a small test flame is passed across the cup.

The lowest temperature at which application of the test flame causesthe vapors above the surface of the sample to ignite is taken as the

flash point.

To find the fire point, the test is continued until the application of thetest flame causes the sample surface to ignite and burn for at least 5sec.


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Specific Gravity Test

In running this test, the asphalt sample is heated until it can be poured. The

material is placed on a pycnometer. The asphalt volume is determined by taking

the difference between the total volume of the bottle and the volume of the water

required to complete the filling. From this information the specific gravity can be

expressed as the ratio of the weight of a given volume of the material at 25 degrees

Celsius or at 15.6 degrees Celsius to that of an equal volume of water at the same

temperature. The following formula may be used to calculate the specific gravity:

Where:

A = weight of pycnometer (plus stopper)

B = weight of pycnometer filled with waterC = weight of pycnometer partially filled with asphalt

D = weight of pycnometer plus asphalt plus water

)()( CDAB

ACavityspecificgr


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PURPOSE & SIGNIFICANCE: Density of a bitumen binder is a fundamental property frequently used as an

aid in classifying the binders for use in paving jobs. In most applications, the bitumen content, when used with aggregate, is

converted into volume basis.

Principle use is the establishment of relationship between binder weight andvolume for transporting and filling purposes.

Specifications for binders in road surfacing are normally expressed aspercentages by weight whereas they are usually shipped and measured in

volume. Also, useful in determining the percentage of voids in mechanically designed

mixtures of bitumens and mineral aggregate. Also, useful in bituminous mix design.


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PROCEDURE:

Weigh the empty pycnometer (W1).

Weigh the pycnometer and sample (W3 ).

Weigh the pycnometer again, filled with water (W2 ).

Fill the pycnometer with sample, mix it thoroughly with water andweigh it again (W4 ).

Finally by using the formula, find out the specific gravity:

Gs = ______ W3-W1______

(W2-W1) - (W4-W3) Test temperature is usually 15.5 C.

It varies from 0.97 to 1.02.


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Composition Tests

Composition tests are done to determine the

proportions of the specific fractions andcomponents of the bituminous binders.


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Solubility Tests

Asphalt consists primarily of bitumen, which are high-molecular-weight hydrocarbons

soluble in carbon disulfide. The bitumen content of a bituminous material is measured

by means of its solubility in carbon disulfide. In the standard test for bitumen content

(ASTM D4), a small sample of about 2 g of the asphalt is dissolved in 100 ml of carbon

disulfide and the solution is filtered through a filtering mat in a filtering crucible. Thematerial retained on the filter is then dried and weighed, and used to calculate the

bitumen content as a percentage of the weight of the original asphalt.

Due to the extreme flammability of carbon disulfide, solubility in trichloroethylene, rather

than solubility in carbon disulfide, is usually used in asphalt cement specifications. The

standard solubility test using trichloroethylene is designated as ASTM D 2042.


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Solubility Tests

SIGNIFICANCE OF TEST

The solubility test is used to detect contamination in asphalt

cement. Specifications for asphalt cements normally require a

minimum solubility in trichloroethylene of 99.0 percent.


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Solubility Tests

PROCEDURE: 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 (cs2).

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.


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Ash Content Tests


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Ash Content Tests

SIGNIFICANCE OF TEST:

This test is carried out on both penetration-grade & cutback bitumen.

In refinery bitumen, the test ensures that undesirable amounts of

mineral matter are not present. This is particularly important for

surface dressing materials.


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Ash Content Tests

PROCEDURE:

Place a 2-5 sample of residue in a weighed porcelain or platinum

crucible and weigh the sample to the nearest 0.1g.

Slow burn off the combustible matter and finally ignite the residue

until the ash is free of carbonaceous matter.

Cool the crucible and content in a desiccators and weigh, reporting

the result as percentage of ash.


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Loss on Heating Tests

When the bitumen is heated it loses the volatility and gets

hardened. About 50gm of the sample is weighed and heated to

a temperature of 1630C for 5hours in a specified oven

designed for this test. The sample specimen is weighed again

after the heating period and loss in weight is expressed as

percentage by weight of the original sample. Bitumen used in

pavement mixes should not indicate more than 1% loss inweight, but for bitumen having penetration values 150-200 up

to 2% loss in weight is allowed.


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SIGNIFICANCE OF TEST: Specifications for penetration-grade asphalt bitumen may require that

the max loss of weight on heating & the max. drop in penetrationshould not exceed particular values.

In practice, the losses in weight & penetration values are almost withinthe specifications requirements. This loss on heating is essentially an accelerated volatilization test. The test is of use only as a general indication of volatile content under

the specified conditions of test.

If the consistency of the residue is compared with that of the original,the amount of hardening resulting from this amount & manner ofvolatilization is all that is indicated.


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PROCEDURE:

A 50gram sample of bitumen is placed in a small container. It is left for 5 hours in a revolving-shelf oven.

The temperature of oven is maintained at 165 C.

At the end of the heating period, the sample is cooled to roomtemperature & weighed.

The loss in weight of the sample is then determined and expressed asa %age of the original weight.The penetration test is often carried out on the residue of the loss-on-

heating test. The result obtained is expressed as a %age of thepenetration of the bitumen before heating.


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Water Content Tests

It is desirable that the bitumen contains minimum water

content to prevent foaming of the bitumen when it is heated

above the boiling point of water. The water in the bitumen is

determined by mixing known weight of specimen in a pure

petroleum distillate free from water, heating and distilling of

the water. The weight of the water condensed and collected is

expressed as percentage by weight of the original sample. Theallowable maximum water content should not be more than

0.2% by weight.


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Water Content Tests

SIGNIFICANCE OF TEST:

Bituminous binders should only contain extremely low moisture

contents if they are to be heated beyond 100 C.

If significant quantities of water are present & this temperature is

exceeded, foaming of the binder will occur.


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Water Content Tests

PROCEDURE: The moisture content of a binder is automatically determined when a distillation test is

carried out. Some time it is desirable to determine the moisture content alone, without carrying out a

complete distillation procedure.

In such instances the moisture content may be determined directly by mixing a specified

amount of binder with a predetermined amount of petroleum spirit (for bitumen) with

which it is immiscible & distilled in a flask or still which is attached to a glass water-cooled

reflux condenser & graduated receiver. Distillation is continued until the volume of water in the receiver is constant. This volume is then measured and expressed as a %age by weight of the original material.


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Distillation


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Distillation

PURPOSE:

It is used to find out the quantity and quality of volatile constituents.

The amount of non-volatile residues present in road tars, cutback bitumen and binderemulsions.

In emulsions, the volatile component is of course water.SIGNIFICANCE OF TEST: The distillation tests are amongst the most valuable of the highway tests for bituminous

binders. The test enable a close check to be kept on the quality of the binders used on road

schemes.

Results also provide very useful information not only on the type of volatiles in the binders,but also on the rate at which these volatiles will be lost under field conditions.

If, for instance, a given cutback is found to speed its volatiles too slow on a given roadscheme, then under similar conditions a cutback with higher boiling range volatiles, asdetermined by the distillation test, can be expected to cure even more slowly.


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Distillation

PROCEDURE:

Two Hundred milliliters of the sample is distilled in a 500 mL

flask at a controlled rate to a temperature of 360 C. Then determine the volume of distillate removed at prescribed

standard temperatures.

testing of asphalt presentation

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