Author Description

Laboratory conditioning of asphalt mixtures during the mix design process to simulate their short-term aging influences the selection of the optimum asphalt content. In addition, long-term conditioning affects the mixture and binder stiffness, deformation, and strength evaluated with fundamental characterization tests to assess mixture performance. The current standard conditioning procedure, AASHTO R 30, Standard Practice for Mixture Conditioning of Hot-Mix Asphalt, was developed over two decades ago. In reviewing whether to update the standard, TRB's National Cooperative Highway Research Program (NCHRP) Research Report 919: Field Verification of Proposed Changes to the AASHTO R 30 Procedures for Laboratory Conditioning of Asphalt Mixtures seeks to (a) develop a laboratory short-term aging protocol to simulate the aging and asphalt absorption of an asphalt mixture during production and transportation based on factors thought to affect aging, and (b) develop a laboratory longer-term aging protocol to simulate the aging of the asphalt mixtures after construction. The key outcome of the research is that the current long-term oven aging (LTOA) procedure in AASHTO R 30 is not realistic. Replacing the aging of a compacted specimen with aging of loose mix for 5 days at 85°C (185°F) before compaction for testing should be considered by the AASHTO Committee on Materials and Pavements.