Internal curing effect of saturated recycled fine aggregates in early-age mortar

This paper explored the potential for internal curing of saturated recycled fine aggregate (RFA) in mortar. Water release from saturated RFAs at various relative humidity (RH) values was investigated using desorption isotherms. Capillary pressure measurements and autogenous shrinkage tests for mortar (W/C = 0.30) with RFA at an early age were used to evaluate water release. The influences of the RFA particle size, water absorption capacity, and dosage were analyzed. Desorption isotherms of the RFAs showed that only 16%-36% of the water they absorbed in 24 h was released at RH > 93%. Retardation of self-desiccation and reduction of early autogenous shrinkage of mortar were observed with saturated RFAs. RFAs with finer particle sizes and higher water absorption capacities gave greater reductions in autogenous shrinkages at the first three days, which could be attributed to the RFA pore structure. Internal curing with the RFA was observed clearly in a mixture with a high aggregate content.