1、Standard Method of Test for Measuring Low-Temperature Flexural Creep Stiffness of Hot-Poured Asphalt Crack Sealant by Bending Beam Rheometer (BBR) AASHTO Designation: T 368-171Technical Section: 4e, Joints, Bearings, and Geosynthetics Release: Group 2 (June 2017) American Association of State Highwa
2、y and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-4e T 368-1 AASHTO Standard Method of Test for Measuring Low-Temperature Flexural Creep Stiffness of Hot-Poured Asphalt Crack Sealant by Bending Beam Rheometer (BBR) AASHTO Designation: T 368-171Technica
3、l Section: 4e, Joints, Bearings, and Geosynthetics Release: Group 2 (June 2017) 1. SCOPE 1.1. This method applies to hot-poured asphalt crack sealant used in the construction and maintenance of roadways as specified by MP 25 and PP 85. 1.2. The method is used to determine the hot-poured asphalt crac
4、k sealant flexural stiffness. It can be used on unaged material or on material aged using T 367. The test apparatus is designed for testing within the temperature range from 4 to 40C. 1.3. The values stated in SI units are to be regarded as the standard. 1.4. This standard covers the determination o
5、f flexural stiffness in hot-poured asphalt crack sealant using the bending beam rheometer and by conducting the creep test. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: MP 25, Performance-Graded Hot-Poured Asphalt Crack Sealant PP 85, Grading or Verifying the Sealant Grade (SG) of a Hot-Poured Asp
6、halt Crack Sealant T 313, Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR) T 367, Accelerated Aging of Hot-Poured Asphalt Crack Sealant Using a Vacuum Oven 2.2. ASTM Standards: D5167, Standard Practice for Melting of Hot-Applied Joint and Crack Sealan
7、t and Filler for Evaluation E1, Standard Specification for ASTM Liquid-in-Glass Thermometers E77, Standard Test Method for Inspection and Verification of Thermometers 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of ap
8、plicable law.TS-4e T 368-2 AASHTO 3. TERMINOLOGY 3.1. Definition: 3.1.1. hot-poured asphalt crack sealanthot-poured modified asphaltic material used in pavement cracks and joints. Note 1Based on the references, hot-poured asphalt crack sealant is typically applied at a temperature of 160C or above.
9、3.2. Definitions of Terms Specific to This Standard: 3.2.1. contact load, nthe load, Pc, required to maintain positive contact between the test specimen, supports, and the loading shaft, 35 10 mN. 3.2.2. flexural creep compliance, D(t), nthe ratio obtained by dividing the maximum bending strain in a
10、 beam by the maximum bending stress. The flexural creep stiffness is the inverse of the flexural creep compliance. 3.2.3. flexural creep stiffness, S(t), nthe creep stiffness obtained by fitting a second order polynomial to the logarithm of the measured stiffness at 8.0, 15.0, 30.0, 60.0, 120.0, and
11、 240.0 s and the logarithm of time. 3.2.4. measured flexural creep stiffness, Sm(t), nthe ratio obtained by dividing the measured maximum bending stress by the measured maximum bending strain. Flexural creep stiffness has been used historically in asphalt technology, while creep compliance is common
12、ly used in studies of viscoelasticity. 3.2.5. average creep ratethe average creep rate obtained by fitting the power law model of the logarithm of the strain versus the logarithm of time. The average creep rate is the absolute value of the exponents of the power law model. 3.2.6. test load, nthe loa
13、d, Pt, of 240 s duration is used to determine the stiffness of the crack sealant being tested, 980 50 mN. 4. SUMMARY OF PRACTICE 4.1. The bending beam rheometer is used to measure the midpoint deflection of a simply supported prismatic beam of hot-poured asphalt crack sealant subjected to a constant
14、 load applied to the midpoint of the test specimen. The device operates only in the loading mode. 4.2. A prismatic test specimen is placed in the controlled temperature fluid bath and loaded with a constant test load for 240.0 s and unloaded for 480.0 s. The test load (980 50 mN) and the midpoint de
15、flection of the test specimen are monitored versus time using a computerized data acquisition system. 5. SIGNIFICANCE AND USE 5.1. This test is intended for hot-poured asphalt crack sealant applied to roadway joints and cracks. 5.2. The test temperature is determined as the lowest temperature experi
16、enced by the pavement surface in the geographical area for which the hot-poured asphalt crack sealant is intended. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 368-3 AASHTO 5.3. The flexural
17、creep stiffness or flexural creep compliance, determined from this test, describes the low-temperature stress-strain-time response of hot-poured asphalt crack sealant at the test temperature. 5.4. The average creep rate determined from this test gives an indication of the rate of deformation of hot-
18、poured asphalt crack sealant at the test temperature. 5.5. Hot-poured asphalt crack sealant must be homogenized before being used to conduct this test. 6. APPARATUS 6.1. A crack sealant bending beam rheometer (CSBBR) test system consists of the following: (1) a modified bending beam rheometer with a
19、 controlled temperature liquid bath that maintains the test specimen at the test temperature, (2) test specimen molds, and (3) items for verifying and calibrating the system. 6.2. Modified Bending Beam RheometerA CSBBR is modified from a typical BBR used for testing asphalt binders according to T 31
20、3. The CSBBR has a modified loading frame system that can accommodate a specimen 12.7 mm in height to operate a three-point bending beam test that applies a constant test load for 240.0 s and unloads for 480.0 s. The specification required by the CSBBR system is in accordance with T 313. The updated
21、 software to be used with a CSBBR test system can be obtained from the instrument manufacturer. 6.3. Test Specimen MoldsTest specimen molds with interior dimensions of 12.70 0.05 mm wide by 12.70 0.05 mm deep by 102.0 0.5 mm long and fabricated from aluminum or stainless steel (Figure 1). 6.3.1. The
22、 thickness of the two spacers used for each mold (small end pieces used in the metal molds) shall be measured with a micrometer and shall not vary from each other in thickness by more than 0.05 mm. Note 2Small errors in the thickness of the test specimen can have a significant effect on the calculat
23、ed stiffness because the calculated stiffness is a function of the thickness, h, raised to the third power. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 368-4 AASHTO Figure 1Dimensions for Cr
24、ack Sealant Bending Beam Rheometer Mold and Modified Specimen Support 6.4. Items for Calibration Items remain the same as in T 313. The only difference is the new calibration kits. The kit contains the new thick and thin stainless steel beam which should be obtained from the instrument manufacturer.
25、 6.5. Calibrated ThermometersCalibrated liquid-in-glass thermometers to verify the temperature transducer of suitable range with subdivisions of 0.1C. These thermometers shall be partial immersion thermometers with an ice point and shall be calibrated in accordance with ASTM E77 at least once per ye
26、ar. A suitable thermometer is designated 133C. An electronic thermometer of equal accuracy and resolution may be used. 6.6. Laboratory OvensTwo standard laboratory ovens capable of producing and maintaining a temperature 200 2C. 2017 by the American Association of State Highway and Transportation Of
27、ficials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 368-5 AASHTO 7. REAGENTS AND MATERIALS 7.1. Bath FluidA bath fluid that is not absorbed by or does not affect the properties of the crack sealant being tested. The bath fluid shall be optically clear at the test tempe
28、rature. 7.2. Binder ClipA binder clip is used to hold the aluminum mold to maintain the size of the sample to prevent shrinkage during sealant cooling. 7.3. Release AgentA proper release agent prevents hot-poured asphalt crack sealant from sticking to the mold. Using a spray type silicon-based relea
29、se agent is recommended. 7.4. SolventA solvent can properly clean the molds, end tabs, and plates. The parts cleaned by the solvent shall be submerged in ethanol prior to use. Cleaning ensures the proper bond between hot-poured asphalt crack sealant and end tabs. 7.5. Cleaning ClothsCloths for wipin
30、g molds, end tabs, and plates. 7.6. Ceramic TileCommercial ceramic tile for heating molds in the oven. 8. HAZARDS 8.1. Standard laboratory caution should be used in handling hot hot-poured asphalt crack sealant in accordance with ASTM D5167, and required safety procedures should be followed when che
31、mical agents are used. 9. VERIFICATION AND CALIBRATION 9.1. Bending Beam Rheometer (BBR)Follow the procedure as stated in T 313. 9.2. Oven and FreezerCalibrate the temperature with a thermometer that meets the requirements of ASTM E1. The thermometer calibration can be verified according to ASTM E77
32、. 10. SAMPLES PREPARATION 10.1. Preparation of Molds: 10.1.1. Spread a very thin layer of release agent on the interior faces of four mold sections to prevent the hot-poured crack sealant from sticking to the metal end pieces. Assemble the mold and use binder clips to hold the pieces of the mold tog
33、ether. 10.1.2. Preheat the oven to a temperature 50C lower than the recommended pouring temperature at least 1 h before testing. Place the mold on the ceramic tiles in the oven 15 m before pouring the asphalt crack sealant. 10.2. Preparation of Test Specimens: 10.2.1. All hot-poured asphalt crack se
34、alant to be tested must undergo the accelerated aging process according to T 367. It is recommended that a minimum of 150 g of hot-poured asphalt crack sealant be prepared and undergo accelerated aging for a set of tests. 10.2.2. Heat four cans of hot-poured asphalt crack sealant, which contain 35 g
35、 of hot-poured asphalt crack sealant each, in an oven set at the sealant manufacturer-recommended pouring temperature until 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 368-6 AASHTO the seala
36、nt is sufficiently fluid to pour. (Do not heat the sealant more than 30 min.) Each can of sealant will be poured into its own mold. 10.3. Molding Test SpecimensPrepare four replicates for each tested sealant. Prior to pouring the sealant, take one preheated mold and one ceramic tile from the oven. W
37、ith the preheated mold on the ceramic tile, firmly stir the sealants prior to pouring into the molds to ensure the homogeneity of the sealant. Begin pouring the sealant from one end of the mold and move toward the other end, slightly overfilling the mold. When pouring, hold the sample container 20 t
38、o 30 mm from the top of the mold, pouring continuously toward the other end in a single pass. Repeat the same procedure for the other three molds. With the filled mold still on the preheated ceramic tile, allow to cool for 1 h to room temperature. After cooling to room temperature, trim the exposed
39、face of the cooled specimens even with the top of the mold using a hot knife. 10.4. Storing and Demolding Test Specimens: 10.4.1. Store all test specimens in their molds at room temperature prior to testing. Testing shall be completed within 4 h after specimens are poured. 10.4.2. Just prior to demo
40、lding, cool the molds containing the test specimens in a cold fluid bath that has the same temperature as the selected test temperature for no longer than 5 min and only long enough to stiffen the test specimen so that it can be readily demolded without distortion. A 15-min interval between each sam
41、ple is desired prior to placing the sample into the cold chamber bath. Do not cool the molds containing the specimens in the test bath because it may cause temperature fluctuations in the bath to exceed 0.2C. 10.4.3. Immediately demold the specimen when it is sufficiently stiff to demold without dis
42、tortion, by disassembling the mold. To avoid distorting the specimen, demold the specimen by sliding the metal side pieces from the specimen. Note 3During demolding, handle the specimen with care to prevent distortion. Full contact at specimen supports is assumed in the analysis. A warped test speci
43、men may affect the measured stiffness. 11. PROCEDURE 11.1. Select the appropriate test temperature for the hot-poured asphalt crack sealant specimen. After demolding, immediately place the test specimen in the testing bath and condition it at the testing temperature. The test specimen shall remain s
44、ubmerged in the bath fluid at the test temperature 0.1C for the entire 60 5 min. 11.2. Check the adjustment of the contact load and test load prior to testing each set of test specimens. The 12.7-mm thick stainless steel beam shall be used for checking the contact load and test load. 11.2.1. Place t
45、he 12.7-mm steel beam in position on the beam supports. Using the test load regulator valve, gently increase the force on the beam to 980 50 mN. 11.2.2. Switch from the test load to the contact load and adjust the force on the beam to 35 10 mN. Switch between the test load and contact load four time
46、s to ensure that the load is stable. 11.2.3. When switching between the test load and contact load, watch the loading shaft and platform for visible vertical movement. The loading shaft shall maintain contact with the steel beam when switching between the contact load and test load; the contact load
47、 and test load shall be maintained at 35 10 mN and 980 50 mN, respectively. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 368-7 AASHTO 11.3. Enter the specimen identification information, incl
48、uding the elapsed time the specimen has been conditioned in the bath at the test temperature, and other information, as appropriate, into the computer that controls the test system. 11.4. After conditioning, place the test specimen on the test supports and gently position the bottom side of the test
49、 specimen against the alignment pins so smoother lateral face will be in contact with the loading shaft. Initiate the test. 11.5. The bath temperature shall be maintained at the selected test temperature 0.1C during the test; otherwise the test shall be rejected. 11.6. The contact load shall be applied by gently increasing the load to 35 10 mN. While applying the contact load, the load on the beam shall not exceed 45 mN, and the time to apply and adjust the contact load shall be no greater than 10 s. 11
