The effect of nano-scale calcium stearate emulsion on the integral waterproof performance and chloride resistance of cement mortar

Cement-based concrete materials are vulnerable to water and aggressive ions owing to hydrophilic and porous structure, which severely reduces their durability. Therefore, it is significant to improve the integral waterproof performance of cement-based concrete materials by using hydrophobic admixture. This paper studied the effect of nano-scale calcium stearate emulsion (NCSE) prepared by using non-ionic surfactant through a nascent saponification method on the integral waterproof performance and chloride resistance of cement mortar. The properties and morphology of calcium stearate emulsions prepared by using different non-ionic surfactants were also studied. The results showed that NCSE with particle size of 321.3 nm, viscosity of 180 mPa.s, good dispersibility, fluidity and storage stability was prepared by using fatty alcohol polyoxyethylene ether O-25 as nonionic surfactant. The introduction of NCSE increased water contact angle on the internal and external surfaces of modified cement mortar. The water contact angle on external surface of modified cement mortar with calcium stearate (CS) content of 1.2 wt% reached 130 degrees. The chloride resistance of cement mortar modified by NCSE was greatly improved. Compared to the blank group, the water absorption of modified cement mortar with CS content of 0.8 wt% at 48 h was reduced by 39.02%, the strength didn't decrease significantly. The water absorption of modified cement mortar with CS content of 1.2 wt% at 48 h was reduced by 51.22%, the compressive strength and flexural strength decreased by 14.96% and 13.95%, respectively.