Equation of state of cementitious materials by ultrasonic methodology

Abstract

The pressure–volume relationship, i.e. the equation of state, was determined for mortar and cement paste samples with a range of pore volume fractions. The equation of state was calculated from the isothermal bulk modulus and its pressure derivative. Ultrasonic techniques were used to determine the bulk modulus as a function of hydrostatic pressures. The ultrasonic velocities were measured up to 0.241 GPa (35 ksi) in increments of 0.0345 GPa (5 ksi). The bulk modulus of the mortar and cement paste samples increased linearly over the examined hydrostatic pressure range. The pressure derivative of the bulk modulus for each sample increased as the pore volume fraction of the samples decreased. The present work demonstrates the capability to determine the equation of state of brittle materials by ultrasonic techniques at hydrostatic pressures. The effect of high strain and high strain rate events, occurring in brittle materials, can be modeled with greater accuracy when incorporating the equation of state.