Influence of curing system on static and dynamic mechanical properties of fly ash concrete

This paper investigates the effect of curing conditions on the static mechanical properties of fly ash concrete such as compressive strength and stress–strain behavior, and utilizes the split Hopkinson pressure bar (SHPB) device to characterize the dynamic mechanical responses of steam-cured concrete under different strain rates. Experimental results reveal that the strength of static concrete decreases with the increase of fly ash (FA) content and increases first and then decreases with the increase of steam curing temperature. The substitution of fly ash for cement reduces water consumption, weakens the hydration degree of cement, and affects the development of static concrete strength. The steam curing temperature plays a role in promoting cement hydration within a certain range, but high temperature leads to the destruction of concrete microstructure, thus inhibiting the development of strength and leading to the instability of concrete performance. The steam curing temperature effects on the dynamic compressive strength of concrete is receded with the increase of strain rate. When the steam curing temperature is constant, the dynamic compressive strength of concrete increases gradually with the increase of strain rate, and the influence of strain rate on the dynamic compressive strength of concrete is greater than that of steam curing temperature. The analysis of the scanning electron microscope (SEM) confirmed that the decrease of concrete strength was due to the change of temperature and fly ash content, which increased microstructure pores, thus affecting the development of strength. This study has important guiding significance to improve the safety of engineering facilities and adapt to the development of modern engineering towards heavy load, long span, and harsh environment.