Characterisation of stone matrix asphalt mixtures

Abstract

This study applied conventional laboratory tests and advanced imaging techniques to experimentally verify the voids in coarse aggregate (VCA) method. Five stone matrix asphalt (SMA) mixtures designed to have different coarse aggregate skeletons were investigated to establish relationships between the VCA ratio, microstructure parameters and the mechanical response of SMA. X-ray CT and image analysis techniques were utilised to non-destructively quantify the microstructure of SMA mixtures. The air void size distributions were quantified with the Weibull cumulative distribution function to describe the packing of the SMA mixtures and to thus verify the existence of a stone-on-stone coarse aggregate skeleton. The dynamic modulus and static creep tests were conducted to measure the mechanical response of the mixture, which describes the structural adequacy of the SMA mixtures. In general, the results showed that the VCA method reasonably identified mixtures with a stone-on-stone coarse aggregate skeleton. The relationships developed recommended that the VCA method be modified to include a lower critical VCA ratio and mechanical testing to ensure optimal performance of SMA.