Internal-curing efficiency of cold-bonded coal bottom ash aggregate for high-strength mortar

•CBBA showed greater mitigation of autogenous shrinkage than RBA.•High-strength mortar with CBBA has similar flow characteristics to that with ES.•Compressive strength of mortar with CBBA is relatively lower than that with ES.•Hydration enhancements in cement paste by RBA and CBBA was less than that by ES.

Herein is reported the results of a study on the internal-curing efficiency of cold-bonded bottom ash aggregates (CBBA) used in high-strength mortar. The flow and compressive strength of high-strength mortar with CBBA were measured. To evaluate the internal curing efficiency of CBBA, the autogenous deformation and internal relative humidity of mortar with pre-wetted CBBA were observed at an early age. In addition, the degree of hydration was measured, and then differential thermal and thermogravimetric analyses (DTA/TGA) were carried out to understand the hydration kinetics of the mortar. The experimental results of mortar with CBBA were compared with those of mortar with raw bottom ash, and with artificial lightweight aggregates. Compared with raw bottom ash, CBBA showed greater mitigation of autogenous shrinkage, meaning that a lower volume proportion of CBBA was sufficient to eliminate autogenous shrinkage in the high-strength mortar.