Effects of laboratory heating, cyclic pore pressure, and cyclic loading on fracture properties of asphalt mixture.
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2012-04-01
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Edition:Final report; Oct. 26, 2009-Apr. 30, 2012.
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Abstract:This study involved the identification and evaluation of laboratory conditioning methods and testing protocols considering heat oxidation, moisture, and load that more effectively simulate asphalt mixture aging in the field, and thereby help to properly assess asphalt mixture property changes over time. In this study, aging was defined as any detrimental effect on asphalt mixture properties during pavement life. Three laboratory conditioning procedures were identified and further developed to evaluate the effects of heat oxidation, moisture, and repeated load: heat oxidation conditioning (HOC), cyclic pore pressure conditioning (CPPC), and repeated load conditioning (RLC) respectively. Results indicated that the most effective approach to effectively induce changes in damage and fracture-related properties involved a combination of HOC and CPPC. HOC was accomplished using the Superpave Long-Term Oven Aging (LTOA) procedure. The combination of LTOA and CPPC was found to effectively induce reduction in failure strain and fracture energy (FE) limit of mixtures to levels consistent with those observed in the field. Although RLC was able to effectively induce damage, the method was found to be impractical because of issues regarding the identification of proper load level to achieve damage without fracture during RLC. The energy ratio (ER) parameter was used for relative comparison of cracking performance of mixtures subjected to similar levels of HOC and CPPC. Results showed that addition of hydrated lime improved cracking performance of granite mixtures, which exhibited higher ER than the limestone mixture tested. In addition, the limestone mixture tested exhibited better cracking performance (higher ER) than the granite mixture without lime. Recommendations were made for additional field and laboratory studies using the conditioning procedures developed in this study.
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