Sulfate freeze–thaw resistance enhancement of cement mortar via a developed hydrophobic mica powder

This study developed hydrophobic mica powder (HMP) using mica powder and stearic acid through high-temperature stirring to enhance cement mortar's resistance to freeze–thaw (F–T) cycles in sulfate environment. Initially, the impact of HMP content on water absorption and compressive strength was assessed. Further tests on cement mortar with varying HMP dosages evaluated sulfate resistance under F–T cycles, including mass loss rate, relative dynamic modulus of elasticity (RDME), and compressive strength. Results indicated that HMP modified mortar reduced water absorption by 62.75% and compressive strength by 5.43% compared to unmodified mortar. After 125 F–T cycles, HMP modified mortar showed minimal damage, with a 7.33% RDME reduction and a 9.12% compressive strength decline. Detailed stress–strain curve analysis led to an axial compression constitutive model incorporating the effects of F–T cycles and HMP contents. This paper elucidates the hydrophobic mechanism of HMP, demonstrating its potential to improve F–T resistance through experimental and microscopic analysis.