1、Standard Method of Test for Determining the Cracking Temperature of Asphalt Binder Using the Asphalt Binder Cracking Device (ABCD) AASHTO Designation: TP 92-141American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2b TP
2、92-1 AASHTO Standard Method of Test for Determining the Cracking Temperature of Asphalt Binder Using the Asphalt Binder Cracking Device (ABCD) AASHTO Designation: TP 92-1411. SCOPE 1.1. This test method covers the determination of cracking temperatures of asphalt binders by the means of an Asphalt B
3、inder Cracking Device (ABCD). This device can be used with unaged material or with material aged using T 240 (RTFOT) or R 28 (PAV), or both. The test apparatus is designed for testing a cracking temperature in the range of 60 to +20C. 1.2. This standard may involve hazardous materials, operations, a
4、nd equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use. 2. REFERE
5、NCED DOCUMENTS 2.1. AASHTO Standards: R 28, Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV) T 240, Effect of Heat and Air on a Moving Film of Asphalt Binder (Rolling Thin-Film Oven Test) 2.2. ASTM Standard: C670, Standard Practice for Preparing Precision and Bias Statement
6、s for Test Methods for Construction Materials 3. TERMINOLOGY 3.1. Definitions: 3.1.1. asphalt binderan asphalt-based cement produced from petroleum residue with or without the addition of particulate organic modifiers of a size less than 250 m. 3.1.2. Invara nickel steel alloy with a low coefficient
7、 of thermal expansion (CTE). The typical CTE of Invar is about 1.2 106/C. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2b TP 92-2 AASHTO 3.2. Description of Terms Specific to This Standard: 3.2.1.
8、ABCD cracking temperaturethe temperature at which a sudden reduction of compressive strain on the ABCD ring occurs due to the fracture of a test specimen during the test specified in this standard. 3.2.2. fracture stressthe maximum tensile stress in the specimen calculated from the strain jump at th
9、e time of fracture. 3.2.3. strain jumpthe amount of strain that the asphalt binder specimen releases when it cracks during the test specified in this standard. 4. SUMMARY OF TEST METHOD 4.1. The asphalt binder cracking device measures the temperature and strain of a restrained asphalt binder ring su
10、bjected to a constant rate of cooling. 4.2. Asphalt binder samples are heated and poured outside of an Invar ring placed in the center of a silicone mold. The Invar ring includes a strain gauge to record the strain applied to it by contraction of the asphalt binder during cooling and a surface-mount
11、ed resistance temperature detector (RTD) to record the temperature of the sample. 4.3. Samples are cooled at a constant rate and the cracking of the asphalt binder sample is represented as a jump in strain on a real-time plot. 4.4. The ABCD cracking temperature is determined by reading the temperatu
12、re at the strain jump on a strain versus temperature plot. 4.5. The strain jump is recorded and, through calculations, the fracture stress of the asphalt binder specimen at the cracking temperature is determined. 5. SIGNIFICANCE AND USE 5.1.1. The thermal cracking temperature can be estimated direct
13、ly without elaborate assumptions and calculations by creating a condition similar to that encountered in the field. 5.1.2. The thermal stress and fracture strength can be determined from strain readings. 5.1.3. The low-temperature thermal cracking performance of asphalt pavements is related to the A
14、BCD cracking temperature of the asphalt binder contained in the pavement. 6. APPARATUS 6.1. Asphalt Binder Cracking Device (ABCD) SystemSystem consisting of the following components: (1) an air-cooled environmental chamber capable of being programmed to cool specimens at a constant rate from a tempe
15、rature of +25C to a temperature of 60C; (2) a computer-controlled data acquisition system capable of real-time display and of recording strain, temperature, and time readings; (3) ABCD rings; and (4) specimen molds. 2015 by the American Association of State Highway and Transportation Officials.All r
16、ights reserved. Duplication is a violation of applicable law.TS-2b TP 92-3 AASHTO 6.1.1. Environmental ChamberAn air-cooled environmental chamber with enough space to test at least four specimens in the molds. The minimum chamber dimensions are 254-mm width, 254-mm depth, and 152-mm height. The temp
17、erature control range shall be from 60C to +25C with 0.5C stability. The chamber shall be equipped with an electronic programming device capable of controlling the cooling and heating rate of the chamber temperatures with an accuracy of 0.5C/h. Note 1Low-temperature operation will result in moisture
18、 condensation inside the test chamber and ABCD rings. Operating the environmental chamber with the temperature control range between 60C and 110C is recommended for periodic drying of the chamber and other test equipment at an elevated temperature. 6.1.2. Data Acquisition System and Real-Time Displa
19、yThe data acquisition system shall record strain, temperature, and time at least every 20 s. The system shall resolve strain to the nearest 0.1, specimen temperature to the nearest 0.1C, and elapsed time to the nearest 1.0 s. In addition, the system shall display the real-time plots of the strain an
20、d temperature to aid manual termination of the test after fracture of the specimens. 6.1.3. ABCD RingThe ABCD ring shall be made of Invar and shall have the following dimensions: 50.8 0.05 mm as the outer diameter, 13.72 0.05 mm in height, and 1.65 0.05 mm in thickness. An electrical strain gauge an
21、d a temperature sensor shall be instrumented inside the ring to measure the strain and the temperature of the ring. Protective top and bottom covers may be attached to the ring using three dowel pins separated by 120 degrees from each other. When the protective covers are used, a strain gauge locati
22、on indicator shall be installed on the top cover as shown in Figure 1. Protective covers shall attach loosely to the ABCD ring, developing no friction at the connections to the ABCD ring during testing. 2015 by the American Association of State Highway and Transportation Officials.All rights reserve
23、d. Duplication is a violation of applicable law.TS-2b TP 92-4 AASHTO Figure 1Dimensions of ABCD Ring 6.1.4. Specimen MoldOne-piece, donut-shaped, silicone rubber molds with 40 Shore Hardness shall be used to prepare and hold the asphalt binder specimens for testing. The outer diameter and the height
24、 of the mold shall be 101.6 0.05 mm and 23.9 0.05 mm, respectively. The dimensions and the cross-sectional view shall be as shown in Figure 2 to yield a test specimen 6.35 0.05 mm thick by 12.70 0.05 mm high by 63.50 0.05 mm in outer diameter with a 6.35 0.05-mm diameter hole at center height. The s
25、ilicone mold shall also have a 6.35 0.05-mm diameter and a 3.18 0.05-mm long hole at the opposite end of the protrusion. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2b TP 92-5 AASHTO Figure 2Dimen
26、sions of Silicone Rubber Mold and Cross-Sectional View Note 2The silicone mold maintains flexibility at the low test temperatures so that no excess strain is applied to the sample or the ABCD ring during testing. Laboratory test results indicate that the silicone rubber mold does not affect the ther
27、mal contraction of asphalt specimens. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2b TP 92-6 AASHTO 6.2. TurntableA 100-by-100-mm flat metal turntable (Figure 3) shall be used to place the silicon
28、e moldABCD ring assembly for pouring hot asphalt binder and to minimize specimen deformation during handling. Figure 3Turntable (101.6 by 101.6 mm in size with 33.0-mm diameter opening) 6.3. OvenAn oven capable of reaching and maintaining a temperature of 180 5C. 6.4. BalanceA top-loading electrical
29、 balance with 1000 g or larger capacity and with 0.1 g or less sensitivity. 6.5. Stainless Steel Syringe (Optional)A stainless steel syringe capable of delivering the predetermined volume (15.6 0.2 cm3at 170C) of asphalt binder sample for four specimens. 7. MATERIALS 7.1. Release AgentA release agen
30、t composed of a 1:1 mass ratio of talc (USP) and glycerin is used around the outside and bottom of the ABCD ring. Note 3Failure to use the release agent will result in the asphalt binder adhering to the ring. This bonding can result in abnormal strain readings and possibly faulty data. 7.2. Soap Wat
31、erMild soap water is used to clean the stained silicone rubber mold. 8. HAZARDS 8.1. Observe standard laboratory safety procedures when handling hot asphalt binder and cleaning with solvents. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplicat
32、ion is a violation of applicable law.TS-2b TP 92-7 AASHTO 9. STANDARDIZATION 9.1. Verification of Strain ReadingVerify the calibration of the strain reading at least every six months and when measurements are suspect. 9.2. Verification of Temperature SensorVerify the calibration of the temperature s
33、ensor at least every six months and when measurements are suspect. 10. PREPARATION OF APPARATUS 10.1.1. Turn on and set the oven to the appropriate temperature for the sample that is being prepared. Allow the oven to heat to the required temperature before placing the asphalt binder into the oven. 1
34、0.1.2. Use a clean cloth or paper towel to thoroughly clean the silicone molds and the rings before testing. 10.1.3. Start the data acquisition system and load the software according to the manufacturers manual for the test system. 11. PREPARATION OF TEST SPECIMENS 11.1. Heat the asphalt binder unti
35、l it is sufficiently fluid to pour. Note 4Insufficient heating may cause the trapping of air bubbles within the specimen. The minimum pouring temperature is one that produces a consistency equivalent to that of SAE 10W30 motor oil (readily pours but not overly fluid) at room temperature. For most PA
36、V-aged asphalt binders, heating at 170C for approximately 1 h produces the optimum consistency for pouring. For most unaged and RTFO aged binders, heating at 150 to 160C for approximately 1 h produces the optimum consistency for pouring. 11.2. Coat the outside and bottom of the ring with a release a
37、gent of talc and glycerin (at a 1:1 mass ratio), and then seat the ring in the silicone mold, ensuring that the ring is level with the top. Do not coat the silicone mold with release agent. The strain gauge on the ring is positioned next to the protrusion as shown in Figure 4 in order to accurately
38、measure the fracture strength. The location of the strain gauge is indicated by the vertical metal dowel pin. Figure 4Silicone MoldABCD Ring Assembly 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2b
39、 TP 92-8 AASHTO 11.3. Place the silicone moldABCD ring assembly at the center of the turntable. From this point on, hold or carry the apparatus by holding the turntable to avoid squeezing the specimen mold. Note 5The silicone mold is very flexible, and holding the silicone mold can cause the specime
40、n to deform and the test results to become less repeatable. 11.4. Record the mass of the mold-ring assembly and the turntable to the nearest 0.1 g. Then place the mold-ring assembly and the turntable on a level surface. 11.5. Remove the heated asphalt binder from the oven. Stir and thoroughly mix th
41、e asphalt binder. Note 6Some asphalt binders with additives tend to separate over time when heated. Therefore, failure to mix the binder can cause varied results in the strength and cracking temperature of the asphalt binder. 11.6. Ensure that the mold-ring assembly is placed on a level surface. The
42、n pour the hot asphalt binder into the mold-ring assembly to fill 14.38 0.5 cm3volume of test specimen when it cools to 25C. Note 7Start pouring at one spot (usually near the protrusion), and let the asphalt binder fill the mold below the protrusion before pouring above the protrusion. Then continue
43、 to pour more binder evenly by rotating the turntable. The binder is poured in a continuous stream as quickly as possible to avoid a drop in temperature or the trapping of air bubbles. Because the annular gap is narrow and binder can spill or overflow, it is recommended to use a stainless steel syri
44、nge specifically made for ABCD sample pouring. When the syringe is not used, determine the required mass to fill 14.38 0.5 cm3at room temperature. Then carefully pour the required mass into the mold-ring assembly placed on an electronic balance. Figure 5ABCD Sample Pouring Device with a Stainless St
45、eel Syringe Note 8The ABCD sample pouring device consists of a microprocessor-controlled heating unit, a cranking unit to lower and raise the plunger, and four graduations to dispense a predetermined volume (15.6 0.2 cm3at 170C) of heated sample per each graduation. The plunger is fitted with a heat
46、 resistant O-ring. The syringe can be heated up to 220C. To prepare four ABCD test specimens, about 80 g of asphalt binder in a 4-oz tin can is needed. Heated asphalt binder is placed so that the tip of the syringe nozzle is touching the bottom of the tin can containing the heated binder. Draw in ab
47、out 20 g of the heated asphalt binder by cranking up the plunger slowly. Slowly dispense the drawn binder completely into the sample tin can. Repeat this “draw-and-dispense” a few times to remove as much air as possible. Slowly draw the heated asphalt binder until the 2015 by the American Associatio
48、n of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2b TP 92-9 AASHTO stopper reaches about 3 mm above the top of the four graduations. Then, place the stopper on the top of the four graduations by dispensing some asphalt binder. Remov
49、e the tin can and wipe out the syringe nozzle. Place the mold-ring assembly so that the specimen forming annular gap is directly below the tip of the nozzle. Turn the stopper to the first graduation. Crank down slowly to lower the plunger and to dispense asphalt binder while turning the mold-ring assembly until the stopper reaches the bottom of the first graduation. Repeat the process to prepare additional samples by placing the next mold-ring assembly under the syringe nozzle
