LAUSR

Abstract The behavior of cementitious materials under severe loadings is of major importance for the security and protection of concrete structures. One of the key mechanical properties of materials subjected to extremely high loading is the relationship between the hydrostatic pressure and the volumetric strain, which is often referred to as the equation of state. In porous materials such as cement paste and mortar, this relationship is substantially inelastic due to the closure and collapse of capillary pores. The paper presents an enhanced theoretical model of the loading branch of the barotropic equation of state for cement paste, mortar, and concrete that utilizes non-linear bulk behavior of cement paste matrix and aggregates. A multi-scale approach is applied to simulate the bulk behavior of cement paste. At the micro-level, the model assumes that the Portland cement paste matrix has the same properties in any concrete or mortar, and the difference in bulk behavior is caused by the difference in pore structure and aggregates. In the presented model, we applied a four-stage equation of state comprising of a trilinear elastic-plastic behavior prior to the closure of the pores followed by a nonlinear Hugoniot-type behavior stage after the closure of the pores at high pressures. At the macro-scale level, the equation of state of the paste is obtained by averaging the micro-domains solutions. The equation of state for the aggregate material is described by the three-stage equation of state with bi-linear elastic-plastic behavior followed by nonlinear Hugoniot-type compaction for the high pressures range. The Hirsch phase mix rule is applied to obtain the equation of state of the composite concrete material. The proposed model allows prediction of the bulk behavior of cementitious composites based on its composition and properties of its components for a wide range of pressures up to extremely high pressures.