Bond-slip behaviour between recycled sand concrete and steel bars

The bond-slip behaviour between concrete and steel bars is an important factor that affects the structural bearing capacity, deformation performance, and durability. In order to explore the applicability of recycled sand concrete in reinforced and prestressed concrete structures, this study conducted center pull-out tests on C40 and C60 recycled sand concrete with 50% and 100% replacement ratios of recycled sand, reinforced with plain bars and ribbed bars. The influence of strength grade and recycled sand replacement ratio on the bond performance of recycled sand concrete with steel bars were analysed. A bond-slip constitutive model for recycled sand concrete was established, and finite element analysis were conducted to validate it. The results showed that the bond failure mode of recycled sand concrete with plain bars and ribbed bars were both characterized by steel bar pull-out failure. With the increase of the strength of recycled sand concrete, the bond strength was also increased. However, as the replacement ratio of recycled sand concrete increases, the bond strength first increased and then decreased. The main reason is that when the replacement ratio was 50%, the hydration reaction was sufficient to improve the interfacial bond strength. A formula for calculating the critical anchorage length of steel bars suitable for recycled sand concrete is proposed. A two-stage constitutive model for the bond-slip behaviour of recycled sand concrete was established, and its accuracy was verified through finite element finite element analysis. This study provides a reference for the application of recycled sand concrete in structures.