Determining Bitumen Content Posted inCivil Engineering Tests| Email This PostBITUMEN CONTENTThis test is done to determine the bitumen content as per ASTM 2172. The apparatus needed to determine bitumen content are - i) Centrifuge extractor ii) Miscellaneous –bowl, filter paper, balance and commercial benzene. A sample of 500g is taken. Procedure to determine bitumen contenti) If the mixture is not soft enough to separate with a t rowel,place 1000g of it in a large pan and warm upto 100 o C to separate the particles of the mixture uniformly. ii) Place the sample (Weight ‘A’) in the centrifuge extractor. Cover the sample with benzene, put the filter paper on it with the cover plate tightly fitted on the bowl. iii) Start the centrifuge extractor, revolving slowly and gradually increase the speed until the solvent ceases to flow from the outlet. iv) Allow the centrifuge extractor to stop. Add 200ml benzene and repeat the procedure. v) Repeat the procedure at least thrice, so that the extract is clear and not darker than the li ght straw colour and record the volume of total extract in the graduated vessel. vi) Remove the filter paper from the bowl and dry in the oven at 110 + 5 o C. After 24hours, take the weight of the extracted sample (Weight ‘B’). REPORTING OF RESULTSBitumen content = [(A-B)/B]×100 % Repeat the test thrice and average the results.
Determining the Ductility Of BitumenPosted in Civil Engineering Tests | Email This Post
This test is done to determine the ductility of distillation residue of cutback bitumen, blown type bitumen
and other bituminous products as per IS: 1208 – 1978. The principle is : The ductility of a bituminous
material is measured by the distance in cm to which it will elongate before breaking when a standard
briquette specimen of the material is pulled apart at a specified speed and a specified temperature.
The apparatus required for this test:
i) Standard mould
ii) Water bath
iii) Testing machine
iv) Thermometer – Range 0 to 44oC, Graduation 0.2oC
Procedure to determine the Ductility Of Bitumen
i) Completely melt the bituminous material to be tested by heating it to a temperature of 75 to 100oC
above the approximate softening point until it becomes thoroughly fluid. Assemble the mould on a brass
plate and in order to prevent the material under test from sticking, thoroughly coat the surface of the
plate and the interior surfaces of the sides of the mould with a mixture of equal parts of glycerine and
dextrin. While filling, pour the material in a thin stream back and forth from end to end of the mould untilit is more than level full. Leave it to cool at room temperature for 30 to 40 minutes and then place it in a
water bath maintained at the specified temperature for 30 minutes, after which cut off the excess bitumen
by means of a hot, straight-edged putty knife or spatula, so that the mould is just level full. ii) Place the
brass plate and mould with briquette specimen in the water bath and keep it at the specified temperature
for about 85 to 95 minutes. Remove the briquette from the plate, detach the side pieces and the briquette
immediately.
iii) Attach the rings at each end of the two clips to the pins or hooks in the testing machine and pull the
two clips apart horizontally at a uniform speed, as specified, until the briquette ruptures. Measure the
distance in cm through which the clips have been pulled to produce rupture. While the test is being done,
make sure that the water in the tank of the testing machine covers the specimen both above and below by
at least 25mm and the temperature is maintained continuously within ± 0.5oC of the specified
temperature.
REPORTING OF RESULTS
A normal test is one in which the material between the two clips pulls out to a point or to a thread and
rupture occurs where the cross-sectional area is minimum. Report the average of three normal tests as
the ductility of the sample, provided the three determinations be within ± 0.5 percent of their mean value.
If the values of the three determinations do not lie within ± 0.5 percent of their mean, but the two higher
values are within ± 0.5 percent of their mean, then record the mean of the two higher values as the test
result.
Determining Penetration of Bitumen
Posted in Civil Engineering Tests | Email This Post This test is done to determine the penetration of bitumen as per IS: 1203 – 1978. The principle is that the
penetration of a bituminous material is the distance in tenths of a mm, that a standard needle would
penetrate vertically, into a sample of the material under standard conditions of temperature, load and
time. The apparatus needed to determine the penetration of bitumen is
i) Penetrometer
ii) Water bath
iii) Bath thermometer – Range 0 to 44oC, Graduation 0.2oC
iii) Light the test flame, adjust it. Supply heat at such a rate that the temperature increase, recorded by
the thermometer is neither less than 5oC nor more than 6oC per minute.
iv) Open flash point is taken as that temperature when a flash first appears at any point on the surface of
the material in the cup. Take care that the bluish halo that sometimes surrounds the test flame is not
confused with the true flash. Discontinue the stirring during the application of the test
flame.
v) Flash point should be taken as the temperature read on the thermometer at the time the flash occurs.
B) FIRE POINT
i) After flash point, heating should be continued at such a rate that the increase in temperature recorded
by the thermometer is neither less than 5oC nor more than 6oC per minute.
ii) The test flame should be lighted and adjusted so that it is of the size of a bead 4mm in dia.
REPORTING OF RESULTS
i) The flash point should be taken as the temperature read on the thermometer at the time of the flameapplication that causes a distinct flash in the interior of the cup.
ii) The fire point should be taken as the temperature read on the thermometer at which the application of
test flame causes the material to ignite and burn for at least 5 seconds.
Determining The Marshall Stability of Bituminous
MixturePosted in Civil Engineering Tests | Email This Post
This test is done to determine the Marshall stability of bituminous mixture as per ASTM D 1559. The
principle of this test is that Marshall stability is the resistance to plastic flow of cylindrical specimens of a
bituminous mixture loaded on the lateral surface. It is the load carrying capacity of the mix at 60oC and is
measured in kg. The apparatus needed to determine Marshall stability of bituminous mixture is
Plot % of bitumen content on the X-axis and stability in kg on the Y-axis to get maximum Marshall
stability of the bitumen mix. A sample plot is given
Pavement materials: Bitumen
Overview
Bituminous materials or asphalts are extensively used for roadway construction, primarily because of their excellentbinding characteristics and water proofing properties and relatively low cost. Bituminous materials consists of bitumenwhich is a black or dark colored solid or viscous cementitious substances consists chiefly high molecular weighthydrocarbons derived from distillation of petroleum or natural asphalt, has adhesive properties, and is soluble in carbondisulphide. Tars are residues from the destructive distillation of organic substances such as coal, wood, or petroleum andare temperature sensitive than bitumen. Bitumen will be dissolved in petroleum oils where unlike tar.
Production of Bitumen
Bitumen is the residue or by-product when the crude petroleum is refined. A wide variety of refinery processes, such asthe straight distillation process, solvent extraction process etc. may be used to produce bitumen of different consistencyand other desirable properties. Depending on the sources and characteristics of the crude oils and on the properties ofbitumen required, more than one processing method may be employed.
Vacuum steam distillation of petroleum oilsIn the vacuum-steam distillation process the crude oil is heated and is introduced into a large cylindrical still. Steam isintroduced into the still to aid in the vaporisation of the more volatile constituents of the petroleum and to minimizedecomposition of the distillates and residues. The volatile constituents are collected, condensed, and the various fractionsstored for further refining, if needed. The residues from this distillation are then fed into a vacuum distillation unit, whereresidue pressure and steam will further separate out heavier gas oils. The bottom fraction from this unit is the vacuum-steam-refined asphalt cement. The consistency of asphalt cement from this process can be controlled by the amount ofheavy gas oil removed. Normally, asphalt produced by this process is softer. As the asphalt cools down to roomtemperature, it becomes a semi solid viscous material.
Cutback bitumenNormal practice is to heat bitumen to reduce its viscosity. In some situations preference is given to use liquid binders suchas cutback bitumen. In cutback bitumen suitable solvent is used to lower the viscosity of the bitumen. From theenvironmental point of view also cutback bitumen is preferred. The solvent from the bituminous material will evaporateand 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 oilThere are different types of cutback bitumen like rapid curing (RC), medium curing (MC), and slow curing (SC). RC isrecommended 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 EmulsionBitumen emulsion is a liquid product in which bitumen is suspended in a finely divided condition in an aqueous mediumand stabilized by suitable material. Normally cationic type emulsions are used in India. The bitumen content in theemulsion is around 60% and the remaining is water. When the emulsion is applied on the road it breaks down resulting inrelease of water and the mix starts to set. The time of setting depends upon the grade of bitumen. The viscosity ofbituminous emulsions can be measured as per IS: 8887-1995. Three types of bituminous emulsions are available, whichare Rapid setting (RS), Medium setting (MS), and Slow setting (SC). Bitumen emulsions are ideal binders for hill roadconstruction. Where heating of bitumen or aggregates are difficult. Rapid setting emulsions are used for surface dressingwork. Medium setting emulsions are preferred for premix jobs and patch repairs work. Slow setting emulsions arepreferred in rainy season.
Bituminous primersIn bituminous primer the distillate is absorbed by the road surface on which it is spread. The absorption therefore dependson the porosity of the surface. Bitumen primers are useful on the stabilized surfaces and water bound macadam basecourses. Bituminous primers are generally prepared on road sites by mixing penetration bitumen with petroleum distillate.
Modified BitumenCertain additives or blend of additives called as bitumen modifiers can improve properties of Bitumen and bituminousmixes. Bitumen treated with these modifiers is known as modified bitumen. Polymer modified bitumen (PMB)/ crumbrubber 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 benoted that the performance of PMB and CRMB is dependent on strict control on temperature during construction. Theadvantages of using modified bitumen are as follows
Lower susceptibility to daily and seasonal temperature variations
Higher resistance to deformation at high pavement temperature
Better age resistance properties
Higher fatigue life for mixes
Better adhesion between aggregates and binder
Prevention of cracking and reflective cracking
Requirements of Bitumen
The desirable properties of bitumen depend on the mix type and construction. In general, Bitumen should possesfollowing desirable properties.
The bitumen should not be highly temperature susceptible: during the hottest weather the mix should not becometoo soft or unstable, and during cold weather the mix should not become too brittle causing cracks.
The viscosity of the bitumen at the time of mixing and compaction should be adequate. This can be achieved byuse of cutbacks or emulsions of suitable grades or by heating the bitumen and aggregates prior to mixing.
There should be adequate affinity and adhesion between the bitumen and aggregates used in the mix.
There are a number of tests to assess the properties of bituminous materials. The following tests are usually conducted toevaluate different properties of bituminous materials.
1. Penetration test2. Ductility test3. Softening point test4. Specific gravity test5. Viscosity test6. Flash and Fire point test
7. Float test8. Water content test9. Loss on heating test
Penetration test
It measures the hardness or softness of bitumen by measuring the depth in tenths of a millimeter to which a standardloaded needle will penetrate vertically in 5 seconds. BIS had standardized the equipment and test procedure. Thepenetrometer consists of a needle assembly with a total weight of 100g and a device for releasing and locking in anyposition. The bitumen is softened to a pouring consistency, stirred thoroughly and poured into containers at a depth at
least 15 mm in excess of the expected penetration. The test should be conducted at a specified temperature of 25 C. Imay be noted that penetration value is largely influenced by any inaccuracy with regards to pouring temperature, size ofthe needle, weight placed on the needle and the test temperature. A grade of 40/50 bitumen means the penetration value
is in the range 40 to 50 at standard test conditions. In hot climates, a lower penetration grade is preferred. TheFigure 1 shows a schematic Penetration Test setup.
Penetration Test Setup
Ductility testDuctility is the property of bitumen that permits it to undergo great deformation or elongation. Ductility is defined as thedistance in cm, to which a standard sample or briquette of the material will be elongated without breaking. Dimension othe briquette thus formed is exactly 1 cm square. The bitumen sample is heated and poured in the mould assembly
placed on a plate. These samples with moulds are cooled in the air and then in water bath at 27 C temperature. The
excess bitumen is cut and the surface is leveled using a hot knife. Then the mould with assembly containing sample iskept in water bath of the ductility machine for about 90 minutes. The sides of the moulds are removed, the clips arehooked on the machine and the machine is operated. The distance up to the point of breaking of thread is the ductilityvalue which is reported in cm. The ductility value gets affected by factors such as pouring temperature, test temperature,rate of pulling etc. A minimum ductility value of 75 cm has been specified by the BIS. Figure 1 shows ductility moulds tobe filled with bitumen.
Softening point testSoftening point denotes the temperature at which the bitumen attains a particular degree of softening under thespecifications of test. The test is conducted by using Ring and Ball apparatus. A brass ring containing test sample ofbitumen is suspended in liquid like water or glycerin at a given temperature. A steel ball is placed upon the bitumen
sample and the liquid medium is heated at a rate of 5 C per minute. Temperature is noted when the softened bitumentouches the metal plate which is at a specified distance below. Generally, higher softening point indicates lowertemperature susceptibility and is preferred in hot climates. Figure 1 shows Softening Point test setup.
Figure 1: Softening Point Test Setup
Specific gravity test
In paving jobs, to classify a binder, density property is of great use. In most cases bitumen is weighed, but when used withaggregates, the bitumen is converted to volume using density values. The density of bitumen is greatly influenced by itschemical composition. Increase in aromatic type mineral impurities cause an increase in specific gravity.
The specific gravity of bitumen is defined as the ratio of mass of given volume of bitumen of known content to the mass of
equal volume of water at 27 C. The specific gravity can be measured using either pycnometer or preparing a cubespecimen of bitumen in semi solid or solid state. The specific gravity of bitumen varies from 0.97 to 1.02.
Viscosity testViscosity denotes the fluid property of bituminous material and it is a measure of resistance to flow. At the applicationtemperature, this characteristic greatly influences the strength of resulting paving mixes. Low or high viscosity duringcompaction or mixing has been observed to result in lower stability values. At high viscosity, it resist the compactive effortand thereby resulting mix is heterogeneous, hence low stability values. And at low viscosity instead of providing a uniformfilm over aggregates, it will lubricate the aggregate particles. Orifice type viscometers are used to indirectly find theviscosity of liquid binders like cutbacks and emulsions. The viscosity expressed in seconds is the time taken by the 50 mbitumen 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 25 C or 10 mm orifice at 25 or 40 C.
Flash and fire point test At high temperatures depending upon the grades of bitumen materials leave out volatiles. And these volatiles catches firewhich is very hazardous and therefore it is essential to qualify this temperature for each bitumen grade. BIS defined the
flash point as the temperature at which the vapour of bitumen momentarily catches fire in the form of flash under specifiedtest conditions. The fire point is defined as the lowest temperature under specified test conditions at which the bituminousmaterial gets ignited and burns.
Float testNormally the consistency of bituminous material can be measured either by penetration test or viscosity test. But forcertain range of consistencies, these tests are not applicable and Float test is used. The apparatus consists of analuminum float and a brass collar filled with bitumen to be tested. The specimen in the mould is cooled to a temperature of
5 C and screwed in to float. The total test assembly is floated in the water bath at 50 C and the time required for waterto pass its way through the specimen plug is noted in seconds and is expressed as the float value.
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 a 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. The allowable maximum water content should not be more than 0.2% by weight.
Loss on heating test
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 163 C 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 notindicate more than 1% loss in weight, but for bitumen having penetration values 150-200 up to 2% loss in weight is allowed.
Table 1: Tests for Bitumen with IS codes
Type of test Test Method
Penetration Test IS: 1203-1978
Ductility test IS: 1208-1978
Softening Point test IS: 1205-1978
Specific gravity test IS: 1202-1978
Viscosity test IS: 1206-1978
Flash and Fire Point test IS: 1209-1978
Float Test IS: 1210-1978
Determination of water content IS: 1211-1978
Determination of Loss on heating IS:1212-1978
Summary
Requirements of bitumen as a binding material and its different forms were discussed. Various tests are conducted on bitumen to
assess its consistency, gradation, viscosity, temperature susceptibility, and safety. Standard test procedures on bitumen were also
covered in this chapter.
Problems
1. The minimum ductility value for bitumen specified by BIS is1. 50cm2. 25cm3. 75cm4. 100cm
2. The allowable maximum water content in bitumen should not be more than
1. 2% by weight2. 0.2% by weight3. 2.5% by weight4. 5% by weight
Solutions
1. The minimum ductility value for bitumen specified by BIS is1. 50cm
2. The allowable maximum water content in bitumen should not be more than1. 2% by weight
2. 0.2% by weight3. 2.5% by weight
4. 5% by weight
Tests on Bitumen Download Transportation Notes
Experience in using bitumen in engineering projects has led to the adoption of certain test procedures that are indicativeof the characteristics that identify adequate performance levels. Some of the tests have evolved with the development ofthe industry and are empirical methods. Consequently it is essential that they are carried out in strict compliance with therecommended procedures if they are to be accurate measurements of the bitumen's properties.
1. Penetration Test
2. Flash Point Test
3. Solubility Test
4. Ductility Test
5. Viscosity Test
Test 1. Penetration Test on Bitumen
The penetration test is one of the oldest and most commonly used tests on asphalt cements or residues from distillation ofasphalt cutbacks or emulsions. The standardized procedure for this test can be found in ASTM D5 [ASTM, 2001]. It is anempirical test that measures the consistency (hardness) of an asphalt at a specified test condition.
Procedure of Penetration Test on Bitumen:
In the standard test condition, a standard needle of a total load of 100 g is applied to the surface of an asphalt or Liquidbitumen sample at a temperature of 25 °C for 5 seconds. The amount of penetration of the needle at the end of 5 secondsis measured in units of 0.1 mm (or penetration unit). A softer asphalt will have a higher penetration , while a harderasphalt will have a lower penetration. Other test conditions that have been used include
1. 0 °C, 200 g, 60 sec., and
2. 46 °C, 50 g, 5 sec.
The penetration test can be used to designate grades of asphalt cement, and to measure changes in hardness due to agehardening or changes in temperature.
Read a detailed procedure of Bitumen Penetration Test with Sample Data
The flash point test determines the temperature to which an asphalt can be safely heated in the presence of an openflame. The test is performed by heating an asphalt sample in an open cup at a specified rate and determining thetemperature at which a small flame passing over the surface of the cup will cause the vapors from the asphalt sampletemporarily to ignite or flash. The commonly used flash point test methods include
1. The Cleveland Open Cup (ASTM D92)2. Tag Open Cup (ASTM D1310).
The Cleveland Open-Cup method is used on asphalt cements or asphalts with relatively higher flash points, while the
Tag Open-Cup method is used on cutback asphalts or asphalts with flash points of less than 79 °C. Minimum flash pointrequirements are included in the specifications for asphalt cements for safety reasons. Flash point tests can also beused to detect contaminating materials such as gasoline or kerosine in an asphalt cement. Contamination of anasphalt cement by such materials can be indicated by a substantial drop in flash point.
When the flash point test is used to detect contaminating materials, the Pensky-Martens Closed Tester method (ASTMD93), which tends to give more indicative results, is normally used. In recent years, the flash point test results have beenrelated to the hardening potential of asphalt. An asphalt with a high flash point is more likely to have a lower hardeningpotential in the field.
Read a detailed procedure of Bitumen Penetration Test with Sample Data
Test 3. Solubility Test on asphalt bitumen
Asphalt consists primarily of bitumens, which are high-molecular-weight hydrocarbons soluble in carbon disulfide. Thebitumen content of a bituminous material is measured by means of its solubility in carbon disulfide.
Procedure for Solubility test on Bitumen
In the standard test for bitumen content (ASTM D4), a small sample of about 2 g of the asphalt is dissolved in 100 ml ofcarbon disulfide and the solution is filtered through a filtering mat in a filtering crucible. The material retained on the filter isthen 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 asASTM D 2042.
The solubility test is used to detect contamination in asphalt cement. Specifications for asphalt cements normally require aminimum solubility in trichloroethylene of 99.0 percent.
Unfortunately, trichloroethylene has been identified as a carcinogen and contributing to the depletion of the earth’s ozonelayer. The use of trichloroethylene will most likely be banned in the near future. There is a need to use a less hazardousand non-chlorinated solvent for this purpose. Results of several investigations have indicated that the solvent n-PropylBromide appears to be a feasible alternative to trichloroethylene for use in this application.
Read a detailed procedure of Bitumen Penetration Test with Sample Data
Test 4. Ductility Test on Asphalt
The ductility test (ASTM D113) measures the distance a standard asphalt sample will stretch without breaking under astandard testing condition (5 cm/min at 25 °C). It is generally considered that an asphalt with a very low ductility willhave poor adhesive properties and thus poor performance in service. Specifications for asphalt cements normallycontain requirements for minimum ductility.
Read a detailed procedure of Bitumen Penetration Test with Sample Data
The viscosity test measures the viscosity of an asphalt. Both the viscosity test and the penetration test measure theconsistency of an asphalt at some specified temperatures and are used to designate grades of asphalts. The advantageof using the viscosity test as compared with the penetration test is that the viscosity test measures a fundamental physicalproperty rather than an empirical value. Viscos ity is defined as the ratio between the appl ied shear stress andinduc ed shear rate of a fluid.
When shear rate is expressed in units of 1/sec. and shear stress in units of Pascal, viscosity will be in units of Pascal-
seconds. One Pascal-second is equal to 10 Poises. The lower the viscosity of an asphalt, the faster the asphalt will flowunder the same stress. For a Newtonian fluid, the relationship between shear stress and shear rate is linear , andthus the viscosity is constant at different shear rates or shear stress . However, for a non-Newtonian fluid, therelationship between shear stress and shear rate is not linear , and thus the apparent viscosity will change as theshear rate or shear stress changes.
Asphalts tend to behave as slightly non-Newtonian fluids, especially at lower temperatures. When different methods areused to measure the viscosity of an asphalt, the test results might be significantly different, since the different methodsmight be measuring the viscosity at different shear rates. It is thus very important to indicate the test method used whenviscosity results are presented.
The most commonly used viscosity test on asphalt cements is the Absolute Viscosity Test by Vacuum CapillaryViscometer (ASTM D2171).
The standard test temperature is 60 °C. The absolute viscosity test measures the viscosity in units of Poise. The viscosityat 60 °C represents the viscosity of the asphalt at the maximum temperature a pavement is likely to experience in mostparts of the U.S. When the viscosity of an asphalt at a higher temperature (such as 135 °C) is to be determined, the mostcommonly-used test is the Kinematic Viscosity Test (ASTM D2170), which measures the kinematic viscosity in units ofStokes or centi-Stokes.
Kinematic viscosity is defined as: When viscosity is in units of Poise and density in units of g/cm, 3 the kinematic viscositywill be in units of Stokes. To convert from kinematic viscosity (in units of Stokes) to absolute viscosity (in units of Poises),one simply multiplies the number of Stokes by the density in units of g/cm
3.
Read a detailed procedure of Bitumen Penetration Test with Sample Data
Composition and Properties of Bitumen
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Composition of Bitumen
Materials in bituminous family are:
1) Tar:
Coal tar is a brown or dark black liquid of high viscosity, which smells of naphthalene and
aromatic hdydrocarbons. Being flammable, coal tar is sometime used for heating or to fire
boilers. It can be used in coal tar soap, and is used in medicated shampoo to kill and repel head
lice, and as a treatment for dandruff.
Depending upon its source of origin, TAR is classified as:
2) Coal Tar:
It is the liquid by-product of the distillation of coal to make coke. The gaseous by-product of this process is commonly known as town gas. It is used for coating of wooden poles and sleepers
It is obtained by the distillation of resinous wood. Wood tar contains creosote and as such has strong preservativeproperties. Search for "resin" in the above search box.
4) Mineral Tar:
It is obtained by the distillation of bituminous shale.
5) Coal Tar Pitch:
It is the residue of the direct distillation of crude tar produced by the high temperature carbonization of coal. It is used as awater proofing compound in masonry, steel and timber structure. It is also used for water proofing concrete structures.
Chemical Composition of Bitumen:
Molecular weight wise, bitumen is a mixture of about 300 - 2000 chemical components, with an average of around 500 -700. Elementally, it is around 95% carbon and hydrogen (± 87% carbon and ± 8% hydrogen), and up to 5% sulfur, 1%
nitrogen, 1% oxygen and 2000ppm metals. Bitumens are composed mainly of highly condensed polycyclic aromatichydrocarbons. They also contain several elements, a number of which are toxic.
Adhesion: Bitumen has the ability to adhere to a solid surface in a fluid state depending onthe nature of the surface. The presence of water on the surface will prevent adhesion.
2. Resistance to Water: Bitumen is water resistant. Under some conditions water may beabsorbed by minute quantities of inorganic salts in the bitumen or filler in it.
3. Hardness: To measure the hardness of bitumen, the penetration test is conducted, whichmeasures the depth of penetration in tenths of mm. of a weighted needle in bitumen after agiven time, at a known temperature.Commonly a weight of 100 gm is applied for 5 sec at a temperature of 77 °F. Thepenetration is a measure of hardness. Typical results are 10 for hard coating asphalt, 15 to40 for roofing asphalt and up to 100 or more for water proofing bitumen.
4. Viscosity and Flow: The viscous or flow properties of bitumen are of importance both at high temperature duringprocessing and application and at low temperature to which bitumen is subjected during service. The flowproperties of bitumens vary considerably with temperature and stress conditions. Deterioration, or loss of thedesirable properties of bitumen, takes the form of hardening. Resultantly , decrease in adhesive and flowproperties and an increase in the softening point temperature and coefficient of thermal expansion.
Introduction to bituminous materials & applications of bitumen
Introduction to Bituminous materials
The term bituminous materials is generally used to denote substances in which bitumen is present or from which it can bederived. Bitumen is defined as an amorphous, black or dark-colored, (solid, semi-solid, or viscous) cementitioussubstance, composed principally of high molecular weight hydrocarbons, and soluble in carbon disulfide. For civilengineering applications, bituminous mate-rials include primarily aphalts and tars. Asphalts may occur in nature (naturalasphalts) or may be obtained from petroleum processing (petroleum asphalts). Tars do not occur in nature and are
obtained as conden-sates in the processing of coal, petroleum, oil-shale, wood or other organic materials. Pitch is formedwhen a tar is partially distilled so that the volatile constituents have evaporated off from it. Bituminous mixtures aregenerally used to denote the combinations of bituminous materials (as binders), aggregates and additives.
This article presents the basic principles and practices of the usage of bituminous materials and mixtures in pavementconstruction. In recent years, the use of tars in highway construction has been very limited due to the concern with thepossible emission of hazardous flumes when tars are heated.
Applications of Bitumen
One of the most important uses for geotextiles is as a filter in drainage and erosion control applications. Drainageexamples include trench and French drains, interceptor drains, blanket drains, pavement edge drains, and structuraldrains, to name just a few. Permanent erosion control applications include coastal and lakeshore revetments, stream and
canal banks, cut and fill slope protection, and scour protection. In all these applications, geotextiles are used to replacegraded granular filters used in conjunction with the drainage aggregate, perforated pipe, rip rap, and so on. When properlydesigned, geotextiles can provide comparable performance at less cost, provide consistent filtration characteristics, andthey are easier and therefore cheaper to install. Although erosion control technically does not improve the soil, preventionof both external and internal erosion in residual and structured soils is an important design consideration.
Geotextiles can also be used to temporarily control and minimize erosion or transport of sediment from unprotectedconstruction sites. In some cases, geotextiles provide temporary protection after seeding and mulching but beforevegetative ground cover can be established. Geotextiles may also be used as armor materials in diversion ditches and atthe ends of culverts to prevent erosion. Probably the most common application is for silt fences, which are a substitute forhay bales or brush piles, to remove suspended particles from sediment-laden runoff water.
Filtration Design Concepts: For a geotextile to satisfactorily replace a graded granular filter, it must perform the same
functions as a graded granular filter:
1. Prevent soil particles from going into suspension2. Allow soil particles already in suspension to pass the filter (to prevent clogging or blinding); and3. Have a sufficiently high permeability and flow rate so that no back pressure develops in the soil being protected.
The factors that control the design and performance of a geotextile filter are
1. Physical properties of the geotextile2. Soil characteristics3. Hydraulic conditions, and4. External stress conditions
The level of design required depends on the critical nature of the project and the severity of the hydraulic and soilconditions. Especially for critical projects, consideration of the risks involved and the consequences of possible failure ofthe geotextile filter require great care in selecting the appropriate geotextile. For such projects and for severe hydraulicconditions, very conservative designs are recommended. As the cost of the geotextile is usually a minor part of the totalproject or system cost, geotextile selection should not be based on the lowest material cost. Also, expenses should not bereduced by eliminating laboratory soil –geotextile performance testing when such testing is recommended by the designprocedure.
The three design criteria which must be satisfied are
For both permeability and clogging, different approaches are recommended for critical/severe applications. Furthermore,laboratory filtration tests must be performed to determine clogging resistance. It is not sufficient to simply rely on retentionand permeability to control clogging potential. Finally, mechanical and index property requirements for durability andconstructibility are given. Constructibility is sometimes called survivability, and it depends on the installation conditions.The best geotextile filter design in the world is useless if the geotextile does not survive the construction operations.
Applications of bituminous materials:
Prefabricated Drains In the last few years, prefabricated geocomposite drainage materials have become available as asubstitute for conventional drains with and without geotextiles. Geocomposites are probably most practical for lateraldrainage situations geocomposites is the use of prefabricated vertical (“wick”) drains to accelerate the consolidation of sof compressible cohesive soil layers. Because they are much less expensive to install, geocomposite drains have madeconventional sand drains obsolete.
It enables traffic stresses to bereduced to acceptable levels insubgrade in the Road CrossSection.
It acts as a working plate form forthe construction of upper
pavement layers. Acts as a drainage layer, by
protecting the subgrade fromwetting up.
It intercept upward movement ofwater by capillary action.
It acts as a separating layer b/wsubgrade and road base. By this it prevent the two layers from mixing up.
b. Characteristics of materials used in Sub Base:
The subgrade material should be clean and free from organic matter and should be able to be compacted by roller, toform stable sub-base. The material should have following characteristic.
Well graded uniformity coefficient (D60/D10) should not be less than 3. Fraction passing sieve #200 shall not be greater than 2/3rd of the fraction passing sieve #40. Should have a L.L not greater than 25%. P.I not greater than 6 CBR should not be less than 25. See also : CBR Test Procedure In coarse grain, aggregate retained by #10 sieve, %age of wear shall not be greater than 5%. The max dia of any particle shall not be greater than 2/3ed of the layer thickness of sub-base.
Typical particle size distribution for the sub-base (granular) when will meet strength requirement are
B.S Sieve Size % By mass of total Aggr passing test sieve
50 100
37.5 80-100
20 60-100
5
30-100
1.15 170-75
0.3 9-50
0075 5-25
* To avoid intrusion of silt and clay material in sub-base from subgrade
It is the layer immediately under the wearig surface (Applies whether the wearing surface is bituminous or cementconcrete and or more inch thick or is but a thin bituminous layer).
As base course lies close under the pavement surface it is subjected to severe loading. The material in a basecourse must be of extremely high quality and its construction must be done carefully.
a. Types of Base Course1. Granular Base Course:
A mixture of soil particles ranging in size from coarse to fine. Processing involve crushing oversized particles andscreening where it is necessary to secure the desired grading. The requirements of a satisfactory soil aggregate surfaceare;
Stability Resistance to abrasion Resistance to penetration of water Capillary properties to replace moisture lost by surface evaporation upon the addition of wearing course
requirement change.
2. Macadam Base:
Successive layers of crushed rock mechanically locked by rolling and bonded by stone screening (rock ductstone chips etc).
3. In-water bound Macadam:
The crushed stones are laid, shaped and compacted and then finer materials are added and washed into surface toprovide a dense material.
4. Treated Bases:
Compose of mineral aggregate and additive to make them strong or more resistant to moisture. Among the treatingagents is bitumen.
4. Surface/Wearing Course in pavement cross section:
The top layers of pavement which is in direct contact with the wheel of the vehicle. Usually constructed of material inwhich bitumen is used as binder materials.
Consists of combination of mineral aggregate with bituminous binder ranging from inexpensive surface treatment ¼ in orless thick to asphaltic concrete.
For good service throughout the full life bituminous pavement must retain following qualities.
Freedom from cracking or raveling. Resistance to weather including the effect of surface water heat and cold. Resistance to internal moisture, particularly to water vapors. Tight impermeable surface or porous surface (if either is needed for contained stability of underlying base or
subgrade). Smooth riding and non skidding surface.
The design should be done so that to meet the above requirements for considerable number of years (need proper designand construction supervision)
Pavement meeting all the requirements above have been product if six distinctly different construction processes asfollows.
Heat a viscous bituminous binder to make it fluid, then in a plant mix it with heated aggregate place and compactthe mixture while it is hot.
Use fluid bituminous binder, mix it with aggregate at normal temperature. Mixing may be done at a plant (plantmix) or on the prepared roadway base (road mix). Spread and compact the mixture at normal temperature.
Add solvent such as naphtha or kerosene to a viscose bituminous binder to make it fluid with aggregate at normaltemperature by either plant or road mix methods. Spread and compact at normal temperature before solventevaporates.
Use fluid emulsion of viscose bituminous binder in water, mix it with aggregate at normal temperature by eitherplant or road mix method. Spread and compact at normal temperature before the emulsion breaks down with itscomponents.
Spread and compact clean crushed aggregate as for water bound macadam. Over it spray heated dissolved oremulsified bituminous binder which penetrates open areas of the rock and binds the aggregate together. Thus iscommonly called “Penetration Method”.
Spread bituminous binder over the roadway surface then cover it with properly selected aggregate. This iscommonly called the “Inverted Penetration Method”.
Selections based on the requirements and economy, large volume of heavy vehicles, low traffic volume etc.
