Study of the waterproof performance and freeze–thaw resistance of cement mortar using stearic-acid-modified mica powder

Stearic-acid-modified mica powder (Sammp) was formulated in an attempt to enhance the water and corrosion resistance of cement mortar. The investigation focused on assessing the freeze–thaw (F/T) resistance of Sammp-modified cement mortars, including the water absorption, surface morphology, relative dynamic elastic modulus (RDEM), compressive strength and uniaxial compression behaviour. The water absorption of the Sammp-modified cement mortars decreased by 53.9–64.4% and they showed exhibited excellent F/T resistance, with the RDEM remaining above 90% after 90 F/T cycles, while the RDEM of control specimens decreased to 60%. After F/T treatment, the compressive strength of unmodified specimens experienced a loss rate of 9.74%, which was 3.7 times, 4.29 times and 1.92 times higher than that of the modified specimens with 1%, 3% and 5% Sammp, respectively. A uniaxial compression constitutive model was established to account for the effects of F/T cycles and Sammp contents on the uniaxial compression behaviour of cement mortar. The model demonstrated a strong and reliable correlation with the experimental data.