Effect of Sodium silicate to hydroxide ratio and Sodium hydroxide concentration on the physico-mechanical properties of geopolymer Binders

Abstract

This paper investigates the effect of silicate to hydroxide ratio and Sodium hydroxide concentration on the physical and mechanical properties of Metakaolin based geopolymer binders. Sodium silicate to Sodium hydroxide ratios of 0.5, 1.0, 1.5 and 2.0 and Sodium hydroxide concentrations of 8 M, 10 M, 12 M and 14 M were studied with the kaolin calcined at 800 oC at testing ages of 7, 14 and 28 days. The mean density of the geopolymer binders was 1.86 g/cm3 which increased with the ratios and concentrations having the maximum density of 1.95 g/cm3. The compressive and flexural strength of the samples increased with testing age (7-28 days) and SS/SH, though above SS/SH = 1, the values gradually decreased. The maximum compressive strength and flexural strength obtained were 14.6 MPa (1MK10 binders) and 3.45MPa (1MK8 binders). The Pareto chart for the compressive strength of the samples showed that both factors contributed significantly to the results.