LABORATORY EVALUATION OF SHAPE AND SURFACE TEXTURE OF FINE AGGREGATE FOR ASPHALT CONCRETE

The evaluation of the shape and surface texture of various fine aggregates was studied. Asphalt concretes using these fine aggregates were evaluated for mix design and deformation under load. Seven different test procedures for evaluating aggregate shape and surface texture were studied. Three sources of fine aggregate with four percentages of crushed material were utilized for both the fine aggregate and the asphalt concrete studies. Of the seven tests for aggregate shape and surface texture, all but the direct shear test provided data that correlated with the percentage of fine aggregate with crushed faces. Best results were obtained from the National Crushed Stone Association (now the National Aggregates Association) test, the Rex and Peck time index, and the specific rugosity. These results were correlated to the Hveem stability of asphalt concrete mixtures designed to a constant 4% air voids using the study aggregates. Similar correlations were performed with Hveem stability and asphalt concrete mixtures with an additional 0.5% asphalt binder. Statistically significant relationships were found between the results of these aggregate tests and the Hveem stabilities.