The interface behavior of recycled concrete aggregate : A micromechanical grain-scale experimental study

Recycled concrete aggregate (RCA) is an excellent substitute of natural aggregates and its use in civil engineering projects has received great attention in recent years. One of the important factors that control the behavior of RCA when used as granular construction material or ballast in geotechnical and infrastructure engineering projects is the mechanical behavior at the contacts of the grains. In the present study, an experimental work is presented investigating the micromechanical behavior of RCA with a focus on the normal and shearing contact response of pairs of grains. Based on these tests, normal and tangential contact stiffness as well as the interface friction coefficient are quantified and thoroughly compared with studies presented in the literature on a broad range of geological and engineered materials. Microscopic image and white light interferometry were applied to inspect changes of grain surface characteristics before and after shearing, while, the basic characterization of the grains was conducted performing SEM analysis, roughness and micro-hardness measurements. The results from the study provide some basic understanding of the contact behavior of RCA interfaces and can be useful in DEM simulations of aggregate assemblies.