Effect of strength of parent concrete on utilization of recycled aggregate concrete: A review

To achieve sustainable recycling of recycled aggregate (RA), it is essential to fully understand the inherent "genetic information" embedded in the parent concrete (PC) strength. This study reveals that PC strength has varying effects on the quality and content of residual mortar in recycled aggregates. An increase in PC strength enhances the quality of the residual mortar, which improves the mechanical properties and durability of both RA and recycled aggregate concrete (RAC). Additionally, higher PC strength results in increased residual mortar content. Higher mortar content has both positive and negative effects on RA. This higher mortar content increases the water absorption capacity of RA, promoting internal curing in RAC and improving its mechanical performance over time. Conversely, it may reduce the physical properties of RA, increase the porosity of RAC, weaken the interfacial transition zone, and thus lower the mechanical performance of RAC. Additionally, this study systematically analyzes the effects of PC strength on the durability of RAC from both macro and micro perspectives. The findings lay a theoretical foundation for the classification and multi-generation recycling of RA, highlighting the critical role of PC strength in optimizing the performance and quality of RA in concrete applications.