Mechanical properties and bond stress-slip behaviour of fly ash geopolymer concrete

Fly ash geopolymer concrete is an eco-friendly alternative to conventional concrete that uses waste materials as a cementitious material. However, there is still a lack in understanding its mechanical properties and bond behaviour that govern the structural performance of reinforced concrete at serviceability and ultimate limits state conditions. Therefore, this study aims to assess the role of the alkaline-activator to binder (AA/B) ratio, the hardened properties, and the bond performance of fly ash geopolymer concrete. The main variables of the pullout specimens are the compressive strength (fc) and concrete cover-to-bar diameter (Cc/bd) ratio. The results show that both compressive and splitting tensile strength (fct) increased with reducing AA/B ratio. A model to accurately predict the splitting tensile strength from the compressive strength is proposed based on the experimental results. Significantly, this study demonstrates that fly ash geopolymer concrete has a high bond strength and is affected by both the compressive strength and the Cc/bd ratio. The bond-slip results available in the literature were used to develop a bond-slip model, and the predicted bond responses were found to agree well with those obtained experimentally in this study. This model can be used to evaluate the bond performance of reinforcement embedded in fly ash geopolymer concrete.