Effect of sand content on bond performance of engineered geopolymer composites (EGC) repair material

Engineered geopolymer composites (EGC) have recently emerged as a greener and more environmentally friendly alternative to conventional engineered cementitious composites (ECC), achieving excellent mechanical and durability properties. This study investigated the effect of sand to binder (S/B) ratio on the bond performance of EGC repair material with concrete and steel reinforcement. The S/B ratio of EGC mixes was varied from 0.3 to 1.0, and its effect on the physical and mechanical properties was evaluated. It was found that increasing the S/B ratio decreased the micro-cracks at the EGC-concrete interface and, increased the bond strength. A direct correlation was observed between the elastic modulus of EGC and its bond strength with concrete substrate. The EGC-steel rebar pull-out strength initially increased and then decreased with the S/B ratio. The EGC repair material with S/B ratio more than or equal to 0.8 achieved the minimum EGC-concrete bond strength value of 1.5 MPa, as recommended by the BSI code.