Combined effect of self-stressing and confinement on GFRP-LC3 interface bond

The load capacity, failure mode and durability of reinforced concrete members are strongly affected by the bond strength between the concrete and the reinforcement. This work presents a physics-based approach to improve the bond strength based on self-stressing effect. Combination of limestone calcined clay cement (LC3) and calcium sulphoaluminate cement (CSA) with different ratios was employed to develop self-stressing function. The addition of CSA induces a remarkable volume expansion of matrix due to the formation of ettringite, it however leads to a decreased compressive strength because of the reduced Portlandite content and increased porosity. A push-out test was conducted to evaluate the interface properties between glass fiber reinforced polymer (GFRP) and LC3-based matrix. The results show that the interface bond strength is highly dependent on the matrix strength under unconfined condition. On the contrary, under confined condition, the interface bond strength increases linearly with the expansion value regardless of matrix strength, attributed to that the self-stressing effect can effectively refine the matrix pores and densify the interface transition zone. The findings from this work demonstrate that the self-stressing effect holds promise to be a plausible method to strengthen the overall properties of reinforced concrete without creating additional carbon emission.