Experimental study on the bonding performance of engineered cementitious composites to normal concrete interface subjected to salt freeze-thaw cycles

This research aims to clarify the damage mechanism of engineered cementitious composites (ECC) to normal concrete (NC) interface under salt freeze-thaw cycles. A comprehensive analysis was conducted to investigate the effects of the interfacial type, ECC strength grade, and the number of salt freeze-thaw cycles on the interfacial bonding performance. The results showed that interfacial failure modes were significantly affected by the interfacial types. Two failure modes (direct shear and fatigue) were observed in the salt freeze-thaw test, and the other two failure modes (bonding material and matrix material) were observed in the direct shear test. Meanwhile, the interfacial shear strength was negatively correlated with the cycle number. Increasing the ECC strength could effectively improve the interfacial bonding performance, especially for specimens with ultra-highperformance concrete (UHPC) bonding. Finally, an interfacial bond-slip degradation model was proposed, which could be used to predict the interfacial salt freeze-thaw damage accurately.