Hydration behaviour of cement in polymer cement waterproof coating and its effect on the macroscopic performance

Abstract

In polymer-cement waterproof coating systems, the polymer emulsion influences the hydration behaviour of the cement component, which in turn affects the macroscopic performance of the coating. In this study, the effects of styrene–acrylate (SA), vinyl acetate copolymer emulsion (VAE), and styrene–butadiene (SB) emulsions on the hydration behaviour of cement and macroscopic properties of waterproofing coatings were investigated through chemical binding water testing; thermogravimetric, X-ray diffraction X-ray photoelectron spectroscopy, and Fourier transform infrared microscopic analyses; and macroscopic property characterisation. Moreover, the mechanism of the chemical reaction between the emulsion and cement was clarified. The degree of cement hydration is the least and most affected by the SB and VAE emulsions, respectively. When the cement proportion in the inorganic phase is 50%, the hydration degree of cement in cases involving SA, VAE, and SB emulsions is 24.87%, 19.57%, and 28.61%, respectively. As the cement proportion in the powder phase increases, the tensile strength and bond strength of the polymer cement waterproof coating increase and the elongation at break decreases. The rate of increase of the tensile strength and rate of decrease of the elongation at break both decrease after the cement content becomes 50%. The SA emulsion complexes with the calcium ions in the hydrated environment, which enhances the interfacial bonding between the organic and inorganic phases and results in excellent macroscopic performance of SA waterproof coatings. The SB emulsion waterproof coating has the best mechanical properties and highest water resistance owing to the highest degree of hydration of cement under the action of SB emulsion and hydrophobicity of the emulsion. The VAE emulsion generates hydrophilic polyvinyl-vinyl alcohol and small molecule products that easily dissolve in alkaline hydration environments, leading to low water resistance of the corresponding waterproof coating.