Compressive strength and hydrolytic stability of fly ash-based geopolymers

Abstract

The process of geopolymerization involves the reaction of a solid aluminosilicate material with a highly alkaline silicate solution that yields an aluminosilicate inorganic polymer named a geopolymer, which may be successfully applied in civil engineering as a replacement for cement. In this study, the influence of the synthesis parameters: solid to liquid ratio, NaOH concentration and the ratio of Na2SiO3/NaOH, on the mechanical properties and hydrolytic stability of fly ash-based geopolymers in distilled water, sea water and simulated acid rain, were investigated. The highest value of compressive strength was obtained using 10 mol dm-3 NaOH and at a Na2SiO3/ /NaOH ratio of 1.5. Moreover, the obtained results showed that the mechanical properties of fly ash-based geopolymers are in correlation with their hydrolytic stability, i.e., factors that increase the compressive strength also increase the hydrolytic stability of fly ash-based geopolymers. The best hydrolytic stability of the fly ash-based geopolymers was shown in seawater while the lowest stability was recorded in simulated acid rain.