Crushing characteristics of a recycled aggregate from waste concrete

A single-particle crushing test was carried out for more than 170 recycled aggregates from waste concrete. Recycled aggregates were sieved into 30- and 40-mm particle size groups, mainly consisting of mortar with 2–10 natural aggregates. At the initial loading of the single aggregate, its irregular surface was close to the loading plate, which eventually crushed it. This first crushing stage is called surface crushing. With further loading, the surface mortar was crushed, and it separated from the aggregate; this process was repeated several times and is called mortar crushing. The natural aggregate was crushed, following several mortar crushing stages, where the load suddenly decreased by more than 50%; this stage is called natural aggregate crushing. As the loading continued, this three-stage crushing cycle was repeated owing to several natural aggregates. The stresses at the initial crack due to the initial natural aggregate crushing and at the peak state seemed to weakly related to the mortar ratio (mass of mortar within each aggregate) and absorption ratio (mass difference before and after soaking). As the number of natural aggregates within each recycled aggregate increased, both stresses slightly increased.