Influence of bonded mortar on recycled aggregate concrete properties: A review

The mortar attached to recycled concrete aggregate (RCA) surface significantly influences the resulting concrete properties due to the high porosity, low strength, and high water absorption. In this study, the physical and mechanical characteristics of RCA and their effects on the fresh, mechanical, and durability properties of the resulting concrete were reviewed with respect to bonded mortar. Owing to the high disparity in the quality of RCA obtained from various sources, a high degree of performance heterogeneity was observed. Concrete produced with RCA is less resistant to crushing, impact, and abrasion than concrete incorporating normal aggregate, because RCA exhibits a lower specific gravity, lower bulk density, and increased porosity. The mechanical properties of concrete also deteriorated with increasing RCA content, indicating that lower values associated with the physical and mechanical properties influenced the hardened concrete properties. This is because of the presence of porous mortar adhered to the surface and higher water absorption, which makes the acid and salt attack by the ingression of sulfate and chloride solution higher than that of the control sample with NA only. In this article, a comprehensive literature review and analysis of the effects of bonded mortar on RCA and the resulting concrete properties were conducted, and prediction equations for the mechanical and durability properties of such concrete were also presented.