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Asphalt Binder Cracking Device to Reduce Low-Temperature Asphalt Pavement Cracking: Final Report
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Final Report May 2011
This report summarizes research into use of the Asphalt Binder Cracking Device (ABCD), a new empirical test method for evaluating the low-temperature cracking potential of asphalt binder. The ABCD test method has been adopted as a Provisional Standard by the American Association of State Highway and Transportation Officials. This report presents the results of two interlaboratory studies that examined the ABCD’s precision and documents the modification of the ABCD procedure to achieve greater precision.
The refinement of the late-stage prototype and inter-laboratory study of the ABCD was supported by a grant from the Highways for LIFE Technology Partnerships Program. The Technology Partnerships Program provided grants to assist general industry make the leap from promising late-stage prototypes to market-ready products and promoted partnerships with State and local highway agencies to demonstrate the technologies under real-world conditions.
This report will be of interest to State and local departments of transportation, Federal Highway Administration division offices, highway research institutions, asphalt manufacturers, and highway construction contractors.
This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.
The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document. Trade names mentioned in this report are not intended as an endorsement of any machine, contractor, process, or product.
Quality Assurance Statement
The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. The FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.
*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380.
The overall scope of the Highways for LIFE grant to EZ Asphalt Technology was to refine the Asphalt Binder Cracking Device (ABCD) test method and to conduct an ABCD interlaboratory study (ILS). During Phase 1, ABCD test equipment and test procedures were re-fined. During Phase 2, five units of ABCD were manufactured and tested in an ABCD ILS. Thirty-one laboratories volunteered for the ABCD ILS. Following manufacturing and testing, ABCD units were delivered to the first five participating laboratories. As a laboratory finished the ILS testing, the unit was repacked and shipped to the next waiting laboratory.
Due to the larger than expected number of volunteering laboratories, the original binder samples prepared for this ABCD ILS ran out in the middle of ILS testing. Replacement binder samples were used for the later part of ABCD ILS testing. However, the analyses of ABCD ILS were based on the data from the 23 laboratories that used the original binder samples. With very limited experience with the ABCD equipment and test procedure, almost all participating laboratories were able to complete the ABCD ILS successfully without major difficulty. Ten laboratories also volunteered to participate in the Bending Beam Rheometer (BBR) Critical Temperature ILS. The results of the ABCD and BBR studies indicated that the precision estimates of ABCD cracking temperature and those of the BBR critical temperature were comparable.
The standard deviation of the ABCD cracking temperature, strain jump, and fracture strength for single-operator ABCD tests were 0.95 ºC (1.71 ºF), 5.48 με, and 0.86 MPa (125 psi), respectively. The standard deviation of the ABCD cracking temperature, strain jump, and fracture strength for multilaboratory ABCD tests were 1.36 ºC (2.45 ºF), 7.21 με, and 1.13 MPa (163.9 psi), respectively. The standard deviations of the BBR critical temperature for single-operator and multilaboratory tests were 0.44 ºC (0.79 ºF) and 0.75 ºC (1.35 ºF), respectively, when the critical temperatures were determined from an interpolation process where the BBR test results from two adjacent grading temperatures bracket the critical values of creep stiffness and m-value. The precision estimates of the BBR critical temperature are better than those of the ABCD cracking temperature. However, the BBR critical temperature alone cannot estimate the proper cracking temperature of asphalt binder. Strength testing must be performed and combined with the BBR test results. Then, the precision of the resulting cracking temperature by BBR would be similar to that of ABCD cracking temperature.
To further improve the precision of ABCD test results, the No-Trim ABCD test procedure was developed. An experiment performed with a limited number of binders showed that the steps for trimming and lubrication of the silicone mold in the current ABCD procedure could be eliminated. Based on these findings, a revised ABCD test procedure was developed and is presented in this report. The No-Trim ABCD test procedure is expected to improve the precision of ABCD test results, especially the multilaboratory precision estimates.
The American Association of State Highway and Transportation Officials (AASHTO) Committee has voted to adopt the ABCD test method as a provisional test method. The ABCD test procedure will be included in a 2011 edition of AASHTO specifications.
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