Effect of Thermal Cycles and Curing Age on Bonding Strength of Cement Mortar Using Manufactured Sand

The bonding of cement mortar to the concrete substrate is crucial in buildings. In this study, cement mortar was prepared using manufactured sand (MS) instead of river sand (RS). The bonding strength between manufactured sand mortar (MSM) and concrete substrate was evaluated and the effects of curing age, water-to-cement ratio (w/c) and thermal cycling on the bonding strength were discussed and compared with those of the river sand mortar (RSM). The compressive strength of the MSM was consistently higher than that of the RSM, while the bonding strength of RSM was consistently higher than that of MSM, indicating that the bonding strength does not depend on the compressive strength of the mortar. As the number of thermal cycles increased, the pull-off strengths at the interface between the concrete and MSM or RSM at different w/c ratios all decreased, and the RSM experienced a larger reduction. After 400 cycles, the percentage decrease in bonding strength of MSM sample ranged from 18.62% to 30.86%.