Simple performance test for moisture damage prediction in asphalt concrete

Developing a highly reliable laboratory test to predict the susceptibility of hot mix asphalt (HMA) concrete to moisture damage remains a challenge to asphalt industry. Pennsylvania State University in cooperation with Advanced Asphalt Technologies, LLC, University of Texas at El Paso, and PaveTex Engineering and Testing, Inc. conducted an extensive research study to develop an improved testing procedure for prediction of moisture damage in HMA. The research, sponsored by National Cooperative Highway Research Program (NCHRP) was conducted in two phases and included eleven different mixes from various states with known field performance. The simple performance tests, developed by NCHRP projects 9-19 and 9-29, were utilized with the Environmental Conditioning System (ECS) and the combined system was used to test moisture damage sensitivity of these mixes. Phase I included the design and execution of an experiment where unconditioned and ECS conditioned specimens were tested using the three Project 9-19 simple performance tests: flow time, flow number, and dynamic modulus. Tests were conducted on three mixtures made from aggregates with good, marginal, and poor resistance to moisture damage based on past research. In addition to the combined ECS/simple performance tests, ASTM D4867 and the Hamburg Wheel Tracking Device were included in the Phase I experiment. The primary conclusion from the Phase I experiment was that the dynamic modulus test was the most suited of the three simple performance tests for possible use with the ECS in an improved moisture sensitivity test. Phase II included eight mixtures with known field performance in regard to moisture damage. Three were good performing mixes and five were poor performing. These mixes were tested with the combined ECS/dynamic modulus system. The mixes were also tested according to ASTM D4867 and the Hamburg Wheel Tracking Device. The results indicated that the dynamic modulus test utilized with the ECS has the potential to discriminate between good and poor performing mixes in regard to stripping and moisture damage.