Effect of process parameters on the performance of fly ash/GGBS blended geopolymer composites

Alkali activation of fly ash and ground-granulated blast-furnace slag (GGBS) is a sustainable technology that promotes recycling of industrial by-products in the form of geopolymer composites. In this study, geopolymers are prepared with fly ash, GGBS, and desert dune sand (fines). The alkaline activator solution is formulated using sodium silicate and 14 M sodium hydroxide solutions. The effect of mixture proportioning and curing conditions on the workability, setting time, and compressive strength of geopolymers was examined. The investigated process parameters included percentage of fly ash replacement by GGBS, superplasticizer dosage, amount of fines, alkaline activator solution content, and sodium silicate to sodium hydroxide ratio. The final geopolymeric product could be enhanced by employing subsequent continuous and intermittent water curing techniques. Based on the experimental results, analytical models correlating mixture proportions with workability and 28-day compressive strength were developed for geopolymers made with 100% GGBS and equal proportions of fly ash and GGBS.