The Effect of Sodium Carbonate on the Fresh and Hardened Properties of Fly Ash-Based One-Part Geopolymer

Abstract

One-part geopolymer utilized dry activator(s) which undergo geopolymerization by "just add water"mechanism. There are wide varieties of dry binders to develop one-part geopolymer. This work presents an investigation of fresh and hardened properties of fly ash-based one-part geopolymer activated by mixture of anhydrous sodium metasilicate (Na2SiO3) with sodium carbonate (Na2CO3). The ratios of alkali activator-to-fly ash (AA/FA) were set as 0.15, 0.20 and 0.25. The substitution of Na2CO3 was set as Na2SiO3/Na2CO3 ratio of 1. Setting time of fresh one-part geopolymer was examined through Vicat needle apparatus. Porosity, compressive strength and microstructural properties of developed specimens were also analyzed after 28 days of curing. The result showed that the partial substitution of Na2CO3 resulted in a shorter setting time and lower porosity. Besides that, the one-part geopolymer activated by the mix of Na2SiO3 and Na2CO3 achieved 78.23 MPa at AA/FA ratio of 0.20. The findings suggest that Na2CO3 is a potential alkali activator for one-part geopolymer.