Chapter 18 Bituminous Materials

Transcription

1 Chapter 18 Bituminous Materials Objective Describe: The different types of bituminous materials used in highway construction,,,,, The processes by which they are obtained,,,,, The tests required to determine those properties that are pertinent to highway engineering,,,,, Description of methods of mix design to obtain a paving material known as asphalt. 2

2 Chapter 18 Bituminous Materials 1- Sources of Asphalt 2- Description and Uses of Bituminous Binders 3- Properties of Asphalt Materials 4- Tests for Asphalt Materials 5- Asphalt Mixtures 6- Superpave Systems 3

3 4- Tests for Asphalt Materials 4

4 4- Tests for Asphalt Materials Tests are conducted on asphalt materials to determine: Consistency of the asphalt materials Quality of the asphalt materials To ascertain whether asphalt materials used in highway construction meet the prescribed specifications. Specifications given by AASHTO (American Association of State Highway and Transportation Officials ) ASTM (American Society for Testing and Materials) The Asphalt Institute. Procedures for selecting representative samples of asphalt for testing have been standardized and are given in MS-18 by the Asphalt Institute and in D140 by the ASTM. Tests for : Asphalt Cements Cutback Asphalts Emulsified Asphalts 5

5 4- Tests for Asphalt Materials Sampling of bituminous materials at points of manufacture, storage, or delivery. Selection of Samples 5.1 Whenever practicable, bituminous materials shall be sampled at the point of manufacture or storage, and at such time as to allow the tests controlling acceptance or rejection to be made in advance of shipment. 5.2 When the samples cannot be taken at the point of manufacture or storage, they shall be taken from the shipment immediately upon delivery. 6. Size of Samples 6.1 The sample size of liquid materials shall be as follows: For routine laboratory examination, 1 L (1 qt) (emulsions 4 L (1 gal)), From bulk storage, 4 L (1 gal), or From barrels or drums, 1 L (1 qt). 6.2 The sample size of semisolid or solid materials shall be as follows: From barrels, drums, or cakes, 1 to 2 kg (2 to 3 lb), or From crushed or powdered material in bulk or bags, 1 to 2 kg (2 to 3 lb). 6

6 7. Containers 4- Tests for Asphalt Materials 7.1 Type of Containers: Containers for liquid bituminous materials, except emulsions, shall be widemouth cans with lined screw caps or triple-seal friction-top cans Containers for emulsified bituminous materials shall be wide-mouth jars or bottles made of plastic, or wide-mouth plastic-lined cans with lined screw caps, or plastic-lined triple-seal friction-top cans Containers for crushed or powdered bituminous materials shall be triple-seal frictiontop cans or plastic sacks placed in other containers suitable for handling. 7.2 Size of Containers: The size of the container shall correspond to the required amount of sample. 8. Protection and Preservation of Samples 8.1 Sample containers shall be new. They shall not be washed or rinsed, or wiped with an oily cloth. If they contain evidence of solder flux, or if they are not clean and dry, they shall not be used. Top and container shall fit together tightly. 8.2 Care shall be taken to prevent the sample from becoming contaminated. Immediately after filling, the container shall be tightly and positively sealed. 8.3 The filled sample container shall not be submerged in solvent, nor shall it be wiped with a solvent saturated cloth. If cleaning is necessary use a clean dry cloth. 8.4 Samples of emulsions shall be protected from freezing by correct packaging. 7

7 1- Consistency Tests The consistency important in pavement construction the consistency at a specified temperature will indicate the grade of the material. temperature significantly affects consistency of asphalt materials (the temperature at which the consistency is determined be specified) asphalt materials can exist in: liquid states semisolid states solid states 8

8 The viscosity used to describe the consistency of asphalt materials in the liquid state, determined by conducting the Saybolt Furol viscosity test the kinematic viscosity test. the penetration used to describe the consistency of asphalt materials in the semisolid and solid states, determined by conducting the penetration test the float test. The ring-and-ball softening point test, 9

9 1- Saybolt Furol Viscosity Test AASHTO T72-83 equipment and procedures for conducting the Saybolt Furol test The Saybolt Furol viscosity is given as the time in seconds for exactly 60 cm3 of the asphalt material to flow through the orifice at temperatures 60 C (140 F). 1- standard viscometer tube, which is 5 in. long and about 1in. In diameter. 2- An orifice of specified shape and dimensions is provided at the bottom of the tube. The orifice is closed with a stopper, and the tube is filled with a quantity of the material to be tested. 3- The standard tube then is placed in a larger oil or water bath and fitted with an electric heater and a stirring device. 10

10 1- Saybolt Furol Viscosity Test AASHTO T The material in the tube is brought to the specified temperature (60 C) by heating the bath. Immediately upon reaching the prescribed temperature, the stopper is removed, and the time in seconds for exactly 60 cm3 of the asphalt material to flow through the orifice is recorded. 5- This time is the Saybolt Furol viscosity in units of seconds at the specified temperature. Temperatures at which asphalt materials for highway construction are tested include 25C (77F), 50C (122F), and 60C (140F). the higher the viscosity of the material, the longer it takes for a given quantity to flow through the orifice. 11

11 1- Saybolt Furol Viscosity Test AASHTO T

12 2- Kinematic Viscosity Test AASHTO Designation T201. equipment and procedures for conducting the Kinematic Viscosity Test Kinematic viscosity, defined as the absolute viscosity divided by the density. The kinematic viscosity of the material in units of centistokes is obtained by multiplying the time in seconds by a calibration factor for theviscometer used. 1- a capillary viscometer tube to measure the time it takes the asphalt sample to flow at a specified temperature between timing marks on the tube. types of viscometer tubes: Zeitfuch s cross-arm viscometer, the Asphalt Institute vacuum viscometer, the Cannon Manning vacuum viscometer. Flow between the timing marks induced by gravitational forces in the Zeitfuch s cross-arm viscometer creating a partial vacuum in the Asphalt Institute vacuum viscometer 13 and Cannon-Manning vacuum viscometer

13 2- Kinematic Viscosity Test AASHTO Designation T201. the cross-arm viscometer is used, placing the viscometer tube in a thermostatically controlled constant-temperature bath A sample of the material to be tested then is preheated and poured into the large side of the viscometer tube until the filling line level is reached. The temperature of the bath then is brought to 135C (275F), Flow then is induced by applying a slight pressure to the large opening or a partial vacuum to the efflux (small) opening of the viscometer tube. This causes an initial flow of the asphalt over the siphon section just above the filling line. Continuous flow is induced by the action of gravitational forces. The time it takes for the material to flow between two timing marks is recorded. The kinematic viscosity of the material in units of centistokes is obtained. 14

14 2- Kinematic Viscosity Test AASHTO Designation T201. the Asphalt Institute vacuum viscometer or the Cannon-Manning vacuum viscometer The test conducted at a temperature of 60C (140F),(AASHTO T202) flow is induced by applying a prescribed vacuum through a vacuum control device attached to a vacuum pump. The product of the time interval and the calibration factor in this test gives the absolute viscosity of the material in poises. 15

15 3- Rotational Viscosity Test AASHTO Designation T equipment and procedures for conducting the Rotational Viscosity Test used to determine the viscosity of asphalt binders at elevated temperatures of 60 C to over 200 C. rotational viscometer that can measure the torque required to rotate a cylinder submerged in a heated sample of the asphalt binder at a required speed. It is performed by submerging the cylindrical spindleمغزل of the viscometer in a specified amount of asphalt sample at the required temperature. The viscometer speed is set at 20 rpm. The torque required to maintain the speed of 20 rpm then is determined. The torque and speed are used to determine the viscosity of the binder in Pascal seconds. 16

16 4- Penetration Test AASHTO - T49 and the ASTM - D5. equipment and procedures for conducting the Penetration Test The penetration test gives an empirical measurement of the consistency of a material in terms of the distance a standard needle sinks into that material under a prescribed loading and time. 1- Penetrometer. 2- A sample of the asphalt cement to be tested is placed in a container which in turn is placed in a temperature-controlled water bath. 3- The sample is then brought to the prescribed temperature of 25 C (77F) and the standard needle (loaded to a total weight of 100 g) is left to penetrate the sample of asphalt for the prescribed time of exactly 5 seconds. The penetration is given as the distance in units of 0.1 mm that the needle penetrates the sample.. The penetration test also can be conducted at 0 C (32F) or at 4 C (39.2F) with the needle loaded to a total weight of 200 g and with penetrations allowed for 60 seconds. 17

17 4- Penetration Test AASHTO - T49 and the ASTM - D5. 18

18 5- Float Test ASTM - D139. equipment and procedures for conducting The float test used to determine the consistency of semisolid asphalt materials that are more viscous than grade 3000 or have penetration higher than 300, since these materials cannot be tested conveniently using either the Saybolt Furol viscosity test or the penetration test. 1- the apparatus consists of an aluminum saucer (float), a brass collar open at both ends, and a water bath. 2- The brass collar is filled with a sample of the material to be tested and then is attached to the bottom of the float and chilled to a temperature of 5 C (41F) by immersing it in ice water. 3- The temperature of the water bath is brought to 50 C (122F), and the collar (still attached to the float) is placed in the water bath which is kept at 50 C (122F). 4- The head gradually softens the sample of asphalt material in the collar until the water eventually forces its way through the plug into the aluminum float. 19

19 5- Float Test ASTM - D139. The time in seconds that expires between the instant the collar is placed in the water bath and that at which the water forces its way through the bituminous plug is the float-test value and is a measure of the consistency. the higher the float-test value, the stiffer the material. 20

20 6- The ring-and-ball softening point test ASTM D equipment and procedures for conducting The ring-and-ball softening point test used to measure the susceptibility of blown asphalt to temperature changes by determining the temperature at which the material will be adequately softened to allow a standard ball to sink through it. 1- small brass ring of 5 8 in. inside diameter and 1 4 in. high, a steel ball 3 8 in. in diameter, and a water or glycerin bath. 2- conducted by first placing a sample of the material to be tested in the brass ring which is cooled and immersed in the water or glycerin bath that is maintained at a temperature of 5 C (41F). 3- The ring is immersed to a depth such that its bottom is exactly 1 in. above the bottom of the bath. 4- The temperature of the bath then is increased gradually, causing the asphalt to soften and permitting the ball to eventually sink to the bottom of the bath. The Softening Point: The temperature in C at which the asphalt material touches the bottom of the bathis recorded as the softening 21 point.

21 6- The ring-and-ball softening point test ASTM D

22 Durability Tests over a period of time asphalt materials subjected to changes in temperature (freezing and thawing) and other weather conditions changes in temperature cause natural weathering of the material,,,,,, lead to; loss of plasticity, cracking, abnormal surface abrasion, failure of the pavement. Evaluation the susceptibility characteristics of asphalt materials to changes in temperature and other atmospheric factors,,,, used,,, the thin film oven test (TFO) 23

23 7- The Thin Film Oven Test (TFO) AASHTO T179. equipment and procedures for conducting The Thin Film Oven Test (TFO) Used to measures the changes that take place in asphalt during the hot-mix process by subjecting the asphalt material to hardening conditions similar to those in a normal hot-mix plant operation. The consistency of the material is determined before and after the TFO procedure using either the penetration test or a viscosity test to estimate the amount of hardening that will take place in the material when used to produce plant hot-mix asphalt. 1- pouring 50 cc of material into a cylindrical flat bottom pan, 5.5 in. (14 cm) inside diameter and 3 8 in. (1 cm) high. The pan containing the sample then is placed on a rotating shelf in an oven and rotated for 5 hours while the temperature is kept at 163C (325F). 24

24 Tests for : Cutback Asphalts Emulsified Asphalts Rate of Curing Tests for curing rates of cutbacks are based on inherent factors which can be controlled. assumption that the external factors are held constant. Volatility and quantity of solvent are used to indicate the rate of curing. The volatility and quantity of solvent may determined from the distillation test; 25

25 8- Distillation Test for Cutbacks AASHTO Designation T78. equipment and procedures for conducting Distillation Test for Cutbacks 1- The apparatus consists principally of a flask in which the material is heated, a condenser, and a graduated cylinder for collecting the condensed material. 2- A sample of 200 cc of the material to be tested is measured and poured into the flask 3- The material is then brought to boiling point by heating it with the burner. 4- The evaporated solvent is condensed and collected in the graduated cylinder. 5- The temperature in the flask is monitored continuously and the amount of solvent collected in the graduated cylinder is recorded when the temperature in the flask reaches 190 C (374F), 225 C (437F), 260 C (500F), and 316 C (600F). The amount of condensate collected at the different specified 26 temperatures gives an indication of the volatility characteristics of the solvent.

26 8- Distillation Test for Cutbacks AASHTO Designation T78. equipment and procedures for conducting Distillation Test for Cutbacks 27

27 9- Distillation Test for Emulsions. AASHTO T59 or ASTM D244. equipment and procedures for conducting Distillation Test for Cutbacks The distillation test for emulsions is similar to that described for cutbacks. difference, is that the glass flask and Bunsen burner are replaced with an aluminum-alloy still and a ring burner. This equipment prevents potential problems emulsified asphalt heated to a maximum of 260C (500F). 28

28 Rheological Tests Dynamic Shear Test AASHTO T Bending Creep Test 29

29 10- Dynamic Shear Test AASHTO T equipment and procedures for conducting Dynamic ShearTest Dynamic Shear Test used to determine; the dynamic (oscillatory) shear modulus and phase angle of a sample of asphalt binder when tested in an oscillatory mode. A Dynamic Shear Rheometer (DSR) test system is used The DSR test system consists of parallel metal plates, an environmental chamber, a loading device, and a data acquisition unit. The test is conducted on test specimens with dimensions of either 1 mm thick and 25 mm in diameter or 2 mm thick and 8 mm in diameter. The test specimen is placed between the parallel metal plates, and one of the plates is oscillated with respect to the other such that strain and stress are controlled. 30

30 11- Bending Creep Test AASHTO T equipment and procedures for conducting Bending Creep Test Indirect loading techniques are used in this test to determine the tensile creep compliance of hot-mix asphalt under different loading times, tensile strength, Poisson s ratio. The test uses an indirect tensile test system consisting of several components including an axial loading device, a load measuring device, devices for measuring specimen deformation, an environmental chamber, 31 and a control and data acquisition system.

31 11- Bending Creep Test AASHTO T A static load of fixed magnitude is applied along the diametrical axis of the test specimen, having dimensions of 38 to 50 mm in height and mm in diameter. The horizontal and vertical deformations near the center of the system are recorded by the data acquisition system and then are used to determine the Poisson s ratio and a tensile creep compliance as a function of time. The tensile strength can be determined immediately after the creep test or later by inducing a constant rate of vertical deformation to failure. 32

32 12- Specific Gravity Test. equipment and procedures for conducting Specific Gravity Test The specific gravity of asphalt materials is used to determine: - the weight of a given volume of material (or vice versa) determine - the amount of voids in compacted mixes correct volumes - to correct volumes measured at high temperatures. Specific gravity is defined as the ratio of the weight of a given volume of the material to the weight of the same volume of water. The specific gravity of bituminous materials changes with temperature which dictates that the temperature at which the test is conducted should be indicated For example, if the test is conducted at 20 C (68F) and the specific gravity is determined to be 1.41, this should be recorded as 1.41/20 C. the asphalt material and the water should be at the sameemperature. The usual temperature at which the specific gravities of asphalt materials are determined is 25 C (77F). Specific gravity ranged from ( g\cm3) 33

33 12- Specific Gravity Test. test normally is conducted with a pycnometer If the material to be tested can flow easily into the ycnometer The dry weight (W1) of the pycnometer and stopper is obtained, the pycnometer is filled with distilled water at the prescribed temperature. The weight (W2) of the water and pycnometer together is determined. The weight W3 then is obtained. The specific gravity of the asphalt material is given as If the asphalt material cannot flow easily, a small sample of the material is heated gradually to facilitate flow and then poured into the pycnometer and left to cool to the specified temperature. The weight W4 of pycnometer and material then is obtained. Water is poured into the pycnometer to completely fill the remaining space not occupied by the material. The weight W5 of the filled pycnometer is obtained. 34 The specific gravity then is given as

34 13- Ductility Test. AASHTO -T51 and ASTM -D113. equipment and procedures for conducting Ductility Test Test Ductility is the distance in centimeters a standard sample of asphalt material will stretch before breaking when tested on standard ductility test equipment at 25C (77F). The result of this test indicates the extent to which the material can be deformed without breaking. the exact value of ductility is not as important as the existence or nonexistence of the property in the material. The test is used mainly for semisolid or solid materials which first are heated gently to facilitate flow and then poured into a standard mold to form a briquette of at least 1 cm2 in cross section. The material then is allowed to cool to 25C (77F) in a water bath. The prepared sample is placed in the ductility machine extended at a specified rate of speed until thread of material joining the two ends breaks. The distance (in centimeters) moved by the machine is the 35 ductility of the material.

35 13- Ductility Test. AASHTO -T51 and ASTM -D113. equipment and procedures for conducting Ductility Test Test 36

36 14- Solubility Test. AASHTO T equipment and procedures for conducting Solubility Test The solubility test is used to measure the amount of impurities in the asphalt material. Insoluble materials include free carbon, salts, and other inorganic impurities. This test is conducted by dissolving a known quantity of the material in a solvent (such as trichloroethylene) and then filtering it through a Gooch crucible. The material retained in the filter is dried and weighed. The test results are given in terms of the percent of the asphalt material that dissolved in the solvent. 37

37 15- Flash-Point Test AASHTO T equipment and procedures for conducting Flash-Point Test The flash point of an asphalt material is the temperature at which its vapors will ignite instantaneously in the presence of an open flame. the flash point normally is lower than the temperature at which the material will burn. The test can be conducted by using: the Tagliabue open-cup apparatus: which is more suitable for materials with relatively low flash points, such as cutback asphalts the Cleveland open-cup apparatus: which is more suitable for materials with higher flash points whereas the Tagliabue 38

38 15- Flash-Point Test AASHTO T equipment and procedures for conducting Flash-Point Test The test is conducted by partly filling the cup with the asphalt material gradually increasing its temperature at a specified rate. A small open flame is passed over the surface of the sample at regular intervals as the temperature increases. The increase in temperature will cause evaporation of volatile materials from the material being tested until a sufficient quantity of volatile materials is present to cause an instantaneous flash when the open flame is passed over the surface. The minimum temperature at which this occurs is the flash point. this temperature gives an indication of the temperature limit at which extreme care should be taken particularly when heating is done over open flames in open containers 39

39 15- Flash-Point Test AASHTO T equipment and procedures for conducting Flash-Point Test 40

40 16- Loss-on-Heating Test AASHTO -T47 equipment and procedures for conducting Loss-on- Heating used to determine the amount of material that evaporates from a sample of asphalt under a specified temperature and time. The result indicates whether asphalt material has been contaminated with lighter materials. conducted by pouring 50 g of the material to be tested into a standard cylindrical tin leaving it in an oven for 5 hours at a temperature of 163 C (325F). The weight of the material remaining in the tin is determined and the loss in weight is expressed as a percentage of the original weight. The penetration of the sample also may be determined before and after the test in order to determine the loss of penetration due to the evaporation of the volatile material. 41

41 17- Water Content Test AASHTO - T55-02 equipment and procedures for conducting Water Content Test The presence of large amounts of water in asphalt materials used in pavement construction is undesirable, and to ensure that only a limited quantity of water is present, specifications for these materials usually include the maximum percentage of water by volume that is allowable. A quantity of the sample to be tested is mixed with an equal quantity of a suitable distillate in a distillation flask that is connected with a condenser and a trap for collecting the water. The sample then is heated gradually in the flask, eventually causing all of the water to evaporate and be collected. The quantity of water in the sample is then expressed as a percentage of the total sample volume. 42

42 18- Demulsibility Test for Emulsion AASHTO T59, ASTM 244 equipment and procedures for conducting Demulsibility Test for Emulsion used to indicate the relative susceptibility of asphalt emulsions to breaking down (coalescing) when in contact with aggregates. Asphalt emulsions are expected to break immediately when they come in contact with the aggregate, so that the material is prevented from washing away with rain that may occur soon after application. A high degree of demulsibility is required for emulsions used for surface treatments, such as RS1 and RS2. A relatively low degree of demulsibility is required for emulsions used for mixing coarse aggregates to avoid having the materials peel off before placing, A very low degree is required for materials produced for mixing fine aggregates. Since calcium chloride will coagulate minute particles of asphalt, 43

43 18- Demulsibility Test for Emulsion AASHTO T59, ASTM 244 equipment and procedures for conducting Demulsibility Test for Emulsion conducted by thoroughly mixing the required standard solution with the asphalt emulsion and then passing the mixture through a No. 14 wire cloth sieve, which will retain the asphalt particles that have coalesced. The quantity of asphalt retained in the sieve is a measure of the breakdown that has occurred. Demulsibility is expressed in percentage as (A/B)100 where A is the average weight of demulsibility residue from three tests of each sample of emulsified asphalt, and B is the weight of residue by distillation in 100 g of the emulsified asphalt. The strength of the test solution used and the minimum value of demulsibility required are prescribed in the relevant specifications. 44

44 19- Sieve Test for Emulsions AASHTO T59-01, ASTM D equipment and procedures for conducting Sieve Test for Emulsions conducted on asphalt emulsions to determine to what extent the material has emulsified the suitability of the material for application through pressure distributors. This test is conducted by passing a sample of the material through a No. 20 sieve and determining what percentage by weight of the material is retained in the sieve. A maximum value of 0.1 percent usually is specified. 45

45 20- Particle-Charge Test for Emulsions AASHTO- T59-01 and ASTM D equipment and procedures for conducting Particle-Charge Test used to identify CRS (Cationic Rapid-Setting ) and CMS (Cationic Medium-Setting ) grades of emulsions. conducted by immersing an anode electrode and a cathode electrode in a sample of the material to be tested passing an electric current through the system, The electrodes then are examined (after some time) to identify which one contains an asphalt deposit. If a deposit occurs on the cathode electrode, the emulsion is cationic 46

46 20- Particle-Charge Test for Emulsions AASHTO- T59-01 and ASTM D equipment and procedures for conducting Particle-Charge Test 47

47 Course Pavement Design - Text books and references Nicholas J.Garber, Lester A. Hoel Traffic and Highway Engineering, SI Edition 2010 chapter 17,18,19, 20, 21, and. Yang H Huang Pavement Analysis and Design Second Edition 2004, Pearson Prentice Hall Yoder E. J., Witczak M. W. Principles of Pavement Design. John Wiley & Sons, INC, New York, REFERENCES: AASHTO Guide for Design of Pavement Structures, American Association of State Highway and Transportation Officials, Washington D,C.,2003 Course Pavement Design Dr.MAJED MSALLAM Isra university 48