Enhancing Geopolymer Performance: Optimization of Sand to Fly Ash and Water to Geopolymer Solid Ratios Using Response Surface Methodology

Abstract

Recently developed Geopolymer is an innovative class of green and high-performance binders. Despite
increasing interests in this unique material, insufficient work is available for optimizing mixture ingredients, which in turn slows the material advancements and its applications. Response Surface Methodology (RSM) has been recently utilized to optimize principal polymeric variables (concentration of sodium hydroxide, sodium silicate to sodium hydroxide ratio and curing temperature) in geopolymer. The aim of this study, is to optimize two basic geopolymer related parameters (sand to fly ash and water to geopolymer solids ratio) for compressive strength and drying shrinkage by developing the statistical models through RSM. The models are verified in a statistical manner and gives any value of geopolymer property with significance level of 95% or higher. Considering the two optimum proportions, consist of 0.64 sand/fly ash and 0.22 water/geopolymer solids. Finally, the optimized results were experimentally validated as the difference between projected and experimental results was found not greater than 5%. The statistical models developed by RSM can be used to navigate geopolymer property and RSM allows designer to obtain an optimal solution of the product that improves its yield and reliability.