Equation of state for saturated concrete: A mesoscopic study

Abstract The equation of state (EoS) plays an important role in accurately predicting the damage and failure of underwater concrete structures with impact and blast loadings. In underwater situations, the capillary pores of concrete are filled with free water, which is known to strongly influence the EoS, with much higher volumetric stiffness for saturated concrete than for dry concrete. In this context, appropriate consideration of the free water effect on the EoS of saturated concrete is essential, which is, however, a complex and expensive task when explored experimentally. In this study, the free water effect is investigated by numerical shock simulations performed on a 3D mesoscopic concrete model comprising mortar and coarse aggregate. Two widely used methods are employed to introduce the free water effect on the EoS of the mortar: the Hugoniot mixing rule and the effective stress law. With the Hugoniot mixing rule, the EoS of the mortar depends on the material properties of its different components and their volume fractions. With the effective stress law, the pressure consists of two parts, one supplied by the dry solid skeleton and the other by the free water. Numerical results reveal that both methods can well reproduce the experiment-supported phenomenon of saturated concrete exhibiting much higher volumetric stiffness than dry concrete. Additionally, the EoS of saturated concrete predicted by the two methods agree well and are mutually verified. Furthermore, it is found that the volume fraction of the coarse aggregate strongly affects the EoS of concrete, while its shape and size gradation have no discernible influences.