Mineral aggregates used in hot mix asphalt (HMA) mixtures have some porosity and tend to absorb some amount of asphalt cement. Several indirect and direct methods for estimating or determining asphaltabsorption have been researched. However, there is a need to study the asphalt absorption phenomenon as related to the physical properties of the mineral aggregate and asphalt cement binder. Eight mineral aggregates of different absorptive characteristics, geologic origin, and mineral compositions were selected from the Strategic HighwayResearch Program Materials Reference Library (SHRP MRL). Four asphalt cements ranging from AC-5 to AC-30 grades were also obtained fromSHRP MRL. A total of 96 HMA mixtures were prepared and tested for asphalt absorption. Physical properties of aggregates (including porecharacteristics) and asphalt cements were determined. Generally, the asphalt absorption decreased with increase in viscosity (at the mixing temperature) of the asphalt cement. A high percentage of maltene (oil) fraction in asphalt cement is likely to increase the total asphalt absorption, possibly because of selective absorption. There appears to be a threshold pore diameter of 0.05 microns in the aggregate below which no appreciable asphalt absorption takes place. The most important pore size range affecting the asphalt absorption appears to be 0.05 to 0.1 microns. (A)
Samenvatting