Enhancing cement mortar hydrophobicity against dry-wet cycling sulfate attack using stearic acid modified mica powder via high-temperature stirring

This study introduces a novel hydrophobic additive (HSA) to bolster the resistance of cement mortar against sulfate attack in dry-wet cycling environment, achieved by modifying mica powder with stearic acid through high-temperature stirring. Initially, the study examined the impact of HSA contents on water absorption and desorption in modified mortar. Concurrently, a series of tests on modified mortar with varying HSA contents explored sulfate resistance in dry-wet cycling environment, encompassing weight loss rate, relative dynamic elastic modulus (RDME), compressive strength, axial compression and sulfate concentration. Analytical findings unveiled a remarkable reduction of 36.24 % in water absorption and 10.09 % in desorption for HSA modified mortar, resulting in substantial decreases in sulfate concentration and convective zone area. Moreover, the HSA modified mortar exhibited minor damage, with an 8.69 % decrease in RDME and a 14.23 % increase in compressive strength under dry-wet cycling sulfate attack. Lastly, the study elucidated the hydrophobic mechanism of HSA modified mortar and established a damage model considering the effects of the erosion time and HSA contents for dry-wet cycling sulfate attack. •A hydrophobic admixture via high-temperature stirring method was developed.•The mechanism of HSA improving the resistance of cement mortar against dry-wet cycling sulfate attack was revealed.•Developing a damage model considering the effects of erosion time and HSA contents.