Use of recycled fine clay brick aggregate as internal curing agent for low water to cement ratio mortar

•The pore size distribution enables water to effectively transfer between the aggregate and cement paste matrix.•The RFCBA could be saturated in a relatively short period with a water absorption larger than 10%•The RFCBA does not significant decrease the strength of the prepared mortar in both short (7-d) and long term period (56-d)•Incorporation of SSD RFCBA can significantly reduce the internal RH drop and drying shrinkage. This paper investigates the feasibility of using recycled fine clay brick aggregate (RFCBA) for the purpose of internal curing and reducing drying shrinkage of mortar. Effects of RFCBA on fresh and hardened properties of mortar were studied. RFCBA was used to replace river sand (in replacement of 30%, 60%, and 100%, respectively) in making the mortar mixes. Besides, the influence of moisture content of the RFCBA was evaluated by varying its pre-wetting time (0, 30 min, 24 h) before the mix preparation. The experimental results show that the initial slump flow decreases with the increasing RFCBA content and pre-wetting time, while an opposite trend is observed for the slum flow loss. The compressive strength and flexural strength of the RFCBA-mortar decrease with an increase in RFCBA content. The reduction of internal relative humidity can be significantly delayed by the RFCBA. Furthermore, the resistance to drying shrinkage of the RFCBA-mortar mixes improves when the RFCBA content increases due to the releasing of the pre-stored water in the porous RFCBA.