Bonding performance between ECC repair layer and salt freeze-thaw damaged NC: Experimental study and theoretical analysis

Engineering cementitious composite (ECC) have been widely applied in the repair of normal concrete (NC) damaged by salt freeze-thaw cycles, owing to their excellent performance. As the weakest part of a composite structure, the bonding mechanism between the ECC repair layer and salt freeze-thaw damaged NC still requires further research. In this study, a splitting tensile test was conducted to explore the effects of the cycle number, interfacial roughness, and interfacial agent on the interfacial bonding performance. The results showed that the interfacial bonding strength was negatively correlated with the cycle number. Compared with specimens that underwent 0 cycles, the interfacial bonding strength decreased from 63 % to 71 % after 200 cycles. The optimal interfacial roughness was approximately 4.5 mm, and an increase in the interfacial roughness further reduced the interfacial bonding strength. Furthermore, the application of interfacial agents significantly enhanced the interfacial bonding strength, with fly ash proving to be the most effective, achieving a notable improvement of 58 %. Finally, a predictive model for the bonding strength of the ECC-NC interface was established. This model offers a theoretical foundation for ECC in repairing NC damaged by salt freeze-thaw cycles. • Bonding performance between ECC repair layer and salt freeze-thaw damaged NC. • A simplified model for rough interface is proposed and an interfacial roughness enhancement coefficient is introduced. • A calculation model of the interfacial bonding strength is established. • The calculation model of the interfacial bonding strength is divided into two categories: (1) Low roughness calculation model; (2) High roughness calculation model.