Surface microscopic properties of various aggregates using laser scanning confocal microscope

Abstract The surface morphology of aggregates has a significant effect on the aggregates, which in turn affects the technical performance of asphalt mixtures and cement concrete. In this study, the surface micro-morphology (SMM) of a) four typical natural aggregates, b) recycled concrete aggregate (RCA), and c) recycled brick aggregate (RCB) were investigated using laser scanning confocal microscope, and combined with image analysis technology, roughness theory and fractal theory for quantitative evaluation. Limewater immersion and physical abrasion were performed on each aggregate to investigate the effect of these processes on SMM. Results show that the surface micro-roughness and fractal dimensions of different aggregates varied predictably with the formation conditions of aggregates. After being immersed in limewater, the surface micro-roughness of basalt, limestone and diabase increased, but their fractal dimensions did not change, while the surface micro-roughness of granite, RCA and RCB decreased by 20–30%, and their fractal dimensions increased by 0.65.%, 1.69% and 0.43%, respectively. The effect of physical abrasion on the SMM of aggregates was related to the hardness of the aggregates. After physical abrasion, the surface micro-roughness and fractal dimensions of the six aggregates were reduced.