Measurements of Moisture Suction and Diffusion Coefficient in Hot-Mix Asphalt and Their Relationships to Moisture Damage

Abstract

A procedure for measuring the total suction in hot-mix asphalt (HMA) mixes was developed in this study. Suction measurements were related to physical and chemical properties of HMA that influence moisture damage. This procedure was achieved in two phases. In the first phase, the total suction was measured in HMA specimens with different types of aggregates and with different air void distributions and aggregate gradations. The results showed that the drying test using a 60°C temperature-controlled room was the most appropriate setup for measuring the total suction in HMA with thermocouple psychrometers. The characteristics of suction–moisture content curves were found to be related to the air void distribution in HMA and to the resistance of the mixtures to moisture damage. In the second phase, total suction was measured in sand asphalt specimens. These specimens had different combinations of aggregates and binders that exhibited different field resistances to moisture damage. The suction measurements were used to calculate the moisture diffusion coefficient. The results revealed that mixes with a higher diffusion coefficient are those that had poor resistance to moisture damage.