Comparative Study on the Performance of Blended and Nonblended Fly Ash Geopolymer Composites as Durable Construction Materials

Abstract

This article represents that the mechanical and microstructural properties and durability of fly ash-based geopolymers blended with silica fume and borax are better than those of conventional fly ash-based geopolymers. Fly ash itself contains the sources of silica and alumina which are required for geopolymerisation. But a sufficient amount of high-reactive silica is able to rapidly initiate geopolymerisation with activation. Pure potassium hydroxide pellets and sodium silicate solution were used for preparation of alkaline activator solution. Fly ash geopolymer paste exhibited better mechanical properties in the presence of silica fume with slight portion of borax. The effect of silica fume-blended geopolymer paste on temperature fluctuation (heating and cooling cycle at certain temperatures) showed better performance than nonblended fly ash-based specimens. Durability property was evaluated by immersion of geopolymer specimens in 10% magnesium sulfate solution for a period of one year. The change in weight, strength, and microstructure was studied and compared. In the magnesium sulfate solution, a significant drop of strength to around 37.26% occurred after one year for nonblended fly ash-based specimens. It is evident that specimens prepared incorporating silica fume had the best performance in terms of their properties.