EVALUATION OF ASPHALT ABSORPTION BY MINERAL AGGREGATES By

iDISCLAIMER The contents of this report reflect the views of the authors who are solely responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the National Center for Asphalt Technology of Auburn University. This report does not constitute a standard, specification, or regulation. ii All mineral aggregates used in the hot mix asphalt (HMA) mixtures have some porosity and as such tend to absorb some amount of asphalt. Different test methods are used by the agencies to determine the amount of asphalt absorbed by the mineral aggregates. There is a need to develop a realistic and accurate standard test method for determining asphalt absorption, especially because of its time dependent nature, so that the void parameters (such as air void content, voids in the mineral aggregate, and voids filled with asphalt) of the compacted mix specimens can be determined uniformly and accurately by all agencies. Three mineral aggregates of different absorptive characteristics and two asphalt cements (AC-20 and AC-5 grades) from the Strategic Highway Research Program (SHRP) Materials Reference Library were used in this study. Although three primary absorption methods were used, a total of nine different conditionings/procedures were attempted. Based on the test results, it has been recommended to use Rice method for determining asphalt absorption after the HMA mix has been aged for 4 hours at 2900F. Also, the asphalt absorption has been found to follow a hyperbolic relationship with time and potentially reaches an ultimate (limiting) value. It is possible, based on this relationship, to predict asphalt absorption at any given time if the absorption values just after mixing and at other two aging times are known