Influence of coarse aggregate size, shape and surface texture on rutting of hot mix asphalt concrete

Abstract

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 were prepared using three types of aggregates: 1) Crushed River gravel, 2) Crushed limestone, 3) Uncrushed river gravel. These seven aggregate blends were used for preparation of test specimens throughout the testing program. This investigation, which consisted largely of laboratory study, was conducted in two phases: 1) An Asphalt concrete mixture study and 2) The characterization of coarse aggregates elongation, shape and surface texture using fractal dimensional analysis. The asphalt concrete mixture analysis was focussed on evaluating permanent deformation characteristics of mixtures made with different percentages of crushed coarse aggregates. An Increase in the percentage of crushed coarse aggregate increased Hveem Stability, Marshall Stability and resistance to creep of hot mix asphalt concrete. The resilient modulus of the specimens was also enhanced by the increase in the amount of crushed aggregate in the mix at high temperatures (115'F). Fractal dimension analysis was shown to be a good technique to characterize aggregate shape and surface texture. Direct correlation was observed between permanent deformation of asphalt concrete and shape characteristics of coarse aggregate particles used in the asphalt concrete mix.