Quantification of concrete aggregate liberation through abrasion comminution

Recycling concrete waste into structural concrete reduces the consumption of raw materials, decreases transport and production energy costs, and saves the use of limited landfill space. Since attached mortar is known for lowering the performance of recycled concrete aggregates (RCA) in concrete applications, current recycling involves the use of RCA as a road base material or in non-structural concrete with low strength requirements, therefore, the application in structural concrete is limited. In general, the applicability of RCA is improved by comminution through various crushing methods. Hereby, the parent particles are cleaved or shattered into a minimum of two particles with a comparable size and a number of much smaller particles. Through this technique, both mortar and aggregates fracture alike, resulting solely in a size reduction. However, to minimise undesirable effects, original natural aggregates (ONA) have to be cleared from attached mortar. Through the use of attrition and shear instead of pressure or impact, surface layers, edges and corners are removed thereby producing particles both slightly smaller and much smaller than the initial. In this study, ONA liberation through abrasion was investigated.