Combined effect of graphene oxide and fly ash on behaviour of high-strength concrete: experimental and numerical investigation

Graphene oxide (GO) is a potential material for application as nano-reinforcements in cementitious composites owing to its high-water dispersibility, aspect ratio and outstanding mechanical characteristics. In this study, the combined effect of GO and fly ash on strength properties, stress–strain behaviour and static modulus of elasticity of high-strength concrete was investigated. In addition, microstructure has been characterized using SEM and EDS techniques. The addition of GO at 0.15% and the replacement of cement with fly ash at 10, 20 and 30% by weight was considered. The results exhibited that the addition of GO at 0.15% improved the compressive and flexural strength of concrete by 24.3 and 25.2%, respectively, at 7 days. The combined effect of GO and fly ash on the strength properties of concrete at 7 days was greater than control concrete demonstrating that GO can offset the effect of fly ash on delaying the strength growth at an early age. From the experimental results, it can be concluded that the addition of GO and fly ash into the concrete improved both the strength and elastic modulus, consequently exhibiting positive synergy in hybridizing GO and fly ash into the concrete. Also, the microstructure properties indicated that the GO and fly ash-based concrete mixes exhibited a denser microstructure. Furthermore, a nonlinear numerical model was also created for GO and fly ash-based concrete with finite element-based software ATENA-GiD to validate the experimental findings. The nonlinear numerical model successfully predicted the behaviour under monotonic axial compression and was quite beneficial in minimizing the tedious experimental testing. Finally, it is found that the findings of both the experimental and numerical investigations are in good agreement.