Results of integrating simple performance tests and environmental conditioning system

Under the guidance of the Strategic Highway Research Program, an environmental conditioning system (ECS) was developed to simulate field conditions to identify the moisture sensitivity of asphalt concrete mixes. However, the system was not included in Superpave® because of poor repeatability. Studies conducted at the University of Texas at El Paso improved the prediction capabilities of the conditioning system. The modified system uses resilient modulus as a moisture sensitivity indicator. Resilient modulus has been commonly used by highway practitioners as an indicator of hot-mix asphalt concrete performance. However, as an extension to the Superpave system, under NCHRP Project 9-19, researchers have proposed simple tests to evaluate the performance of asphalt concrete. These tests are referred to as dynamic modulus, flow number, and flow time. The objective of this study was to evaluate the potential of these tests, when integrated with an ECS, to predict moisture damage in lieu of the resilient modulus. Three mixes of known performance were selected and conditioned by using a conditioning procedure of the modified system. The simple performance tests were done on unconditioned as well as ECS-conditioned specimens. The integration results indicate that the flow number and flow time tests, as conducted during this study, do not have the potential to replace resilient modulus in ECS for identification of moisture-susceptible asphalt concrete in the present form. However, the dynamic modulus test demonstrated their potential as a performance indicator replacing the resilient modulus test. The results of the integration efforts are presented here.