Freezing behavior of cement pastes saturated with NaCl solution

• Freezing strains of cement pastes saturated with salt solution are measured.
• Thermal expansion coefficient of dried samples relates to cement hydrates.
• Pore ice content is evaluated from phase change law and pore structure.
• Liquid pressure dominates over interfacial energy during pore freezing.
• Poroelastic model predicts reasonably well the freezing strains in first cycle.

This study investigates the freezing behaviors of two cement pastes saturated with water and salt (NaCl) solutions of different concentrations. Special experimental set-up was designed to measure the freezing strains of cylindrical specimens in undrained condition. Using the interfacial curvature properties involved in mercury intrusion under pressure and ice penetration under freezing, the pore ice saturation degree is evaluated through mercury intrusion porosimetry (MIP) data. Experimental results show that both porosity and pore connectivity have impact on the ice saturation degree during freezing. Poromechanical model is established for the freezing strain in the first cooling phase, and the poromechanical simulation agrees reasonably well with the measured strains. The modeling puts in evidence: (1) the freezing strain is induced by pore pressure and thermal contraction of solid matrix, and (2) among the pore pressure contributions the liquid pressure dominates over the interface energy contribution.