Experimental and numerical investigation of bond behavior between geopolymer based ultra-high-performance concrete and steel bars

• A total of twenty groups of specimens were tested to investigate bond behavior between G-UHPC and steel bars. • The failure modes and bond stress-slip relationships were analyzed in detail. • A detailed 3D numerical model was developed and validated against the experimental findings. • A bond stress-slip constitutive model was proposed to precisely predict the bond behavior between G-UHPC and the steel bars. In this study, a total of twenty groups of specimens were tested to investigate bond behavior between the geopolymer based ultra-high-performance concrete (G-UHPC) and steel bars. The failure modes and bond stress-slip relationships were analyzed and discussed in detail. Subsequently, a detailed 3D numerical model was developed and validated against the experimental findings. The validated numerical model was then employed to perform parametric studies to evaluate the effects of steel strength, bond length, and protective layer thickness on the bond behavior between G-UHPC and the steel bar. It was revealed that the bond strength between the steel bar and G-UHPC was enhanced upon increasing the steel bar strength and protective layer thickness, along with reducing the steel bar diameter. The bond slip decreased with an increase in the steel fiber length and volume fraction. Further, the protective layer thickness exhibited an insignificant effect on the linear ascending stage of the bond stress-slip relationships, but positively impacted the maximum bond strength of the specimen. Finally, a bond stress-slip constitutive model was proposed to precisely predict the bond behavior between G-UHPC and the steel bars.