Curing sensitivity and rational curing period for recycled aggregate concrete

This study illustrates the strength development models for recycled aggregate concrete (RAC) exposed to different curing regimes. Additionally, the present study examines the curing sensitivity, and the minimum curing period required to develop specified strength and durability for RAC composed of high-quality recycled concrete aggregate (RCA). RAC is observed to be lower curing sensitive than natural aggregate concrete (NAC). RAC with ordinary Portland cement (OPC) and RAC with Portland pozzolana cement (PPC) are approximately equal in curing sensitivity. RAC durability is significantly impacted by water curing on the first day. First-day water curing reduces RAC (OPC) and RAC (PPC) sorptivity by 42.85% and 45.54%, respectively. Moisture loss, especially within three days of casting, affects RAC strength over time. Contrary to the stipulated minimum curing period (7 days-10 days) for NAC to achieve 70% of the specified compressive strength, RAC (OPC) and RAC (PPC) require a minimum curing period of only 2.32 days and 1.62 days, respectively, to achieve 80% of the specified compressive strength. Following curing, RAC develops structural integrity and internal compactness in one to three days. In terms of internal compactness and uniformity, RACs cured for more than three days have no significant impact. It is possible to consider the initial curing of RAC for 7 days as the maximum curing period since it can develop 100% of its compressive strength within 90 days to 100 days. RAC (OPC) cured for more than two days, and RAC (PPC) cured for more than one day may meet the requirements of chloride-ion penetration less than 1000 Coulombs and electrical resistivity of more than 208 Ohm-m.