Effect of Composition on Waterproofing Property of Silicone Modified Polyacrylate Emulsion-Sulphoaluminate Cement Composite Coating: Optimization by Response Surface Methodology

Polymer-modified cementitious coatings are considered to be one of the most promising waterproofing materials. In this paper, response surface methodology (RSM) is used to optimize composition of silicone modified polyacrylate emulsion (SPA)-sulphoaluminate cement (SAC) composite coating (SSCC) based on improvement of waterproofing property. Being considered as the most important factors, the ratios of SAC to SPA, REP (redispersion emulsion powder) to SPA and SiO2 to SPA are studied. The results show that the quadratic polynomial model fits experiment data fairly well, and R-2 and Adj-R-2 values for water absorption are 0.9852 and 0.9662, respectively. The differences observed from variation of SAC/SPA and REP/SPA are extremely significant. The water absorption of SSCC decreases first and increases afterwards with increasing the ratio of SAC to SPA. And a trend caused by REP/SPA is gradually decreasing. By contrast, the factor of SiO2/SPA is not that significant. The optimal ranges, taken all factors into consideration, are 0.8-1.0 for SAC/SPA, 0.10-0.11 for REP/SPA and 1.1-1.3 for SiO2/SPA. In this case, the water absorption ratio can drop to 4.25%.