This study was part of the Strategic Highway Research Program (SHRP) A-003A contract undertaken as an interim evaluation of the hypotheses concerning the influence of binder properties on the moisture susceptibility of asphalt-aggregate mixes. Thirty-two mixes using eight asphalts and four aggregates from the Materials Reference Library (MRL) were used to fabricate roller-compacted slabs from which specimens were sawed or cored. These mixes were tested by four procedures: (1) Environmental Conditioning System (ECS), (2) Oregon State University (OSU) Wheel Tracker, (3) SWK Pavement Engineering/University of Nottingham (SWK/UN) Wheel Tracker and (4) Net Adsorption Test (NAT). Because the water-conditioning and testing procedures were different, it was not appropriate to make direct comparisons of results or to use the results for ranking materials. The ECS was the only test to compare dry- or wet-conditioned mixes, while the two wheel trackers tested only wet-conditioned mixes. The NAT was not directly comparable because it considered only adhesion. The two rutting tests provided results that were similar to the A-002A hypothesis, but did not confirm hte ECS results. It was concluded that, for water-sensitivity, asphalts or aggregates could not be ranked alone but that combinations or pairs were more appropriate because of strong interactions.
Abstract