Influence of Coarse Aggregate Shape and Surface Texture on Rutting of Hot Mix Asphalt Concrete (1244-6)

The objectives of this study were to: 1) evaluate the influence of coarse aggregate shape and surface texture on deformation characteristics of asphalt concrete, 2) characterize aggregate elongation, shape, and texture using fractal dimensional analysis, and 3) study the correlation between the physical properties of coarse aggregates and the permanent deformation characteristics of asphalt concrete. In order to study the influence of coarse aggregate type on the properties of asphalt concrete mixture, seven different blends of aggregates of the same gradation were prepared using three types of aggregates: 1) uncrushed river gravel, 2) crushed river gravel, and 3) crushed limestone. These seven aggregate blends were used to prepare specimens for a laboratory testing program.|The laboratory investigation was conducted in two phases: 1) an asphalt concrete mixture study and 2) the characterization of coarse aggregate elongation, shape, and surface texture using fractal dimensional analysis. The asphalt concrete mixture analysis focused on evaluating permanent deformation characteristics of mixtures made with different percentages of crushed coarse aggregate. An increase in the percentage of crushed coarse aggregate resulted in increased Hveen and Marshall stability and increased resistance to creep and permanent deformation of hot mix asphalt concrete. Resilient modulus of the specimens was also enhanced by increasing the amount of crushed aggregate in the mix at high temperature (115øF [or 40øC]). Fractal dimension analysis was shown to be a viable technique for characterizing aggregate particle shape and surface texture. Researchers found a direct correlation between permanent deformation of asphalt concrete mixtures and shape characteristics of coarse aggregate particles used in mixtures