A Study on Properties of Geopolymer Mortar Made from Fly Ash Incorporated Natural Zeolite

Abstract

This article presented properties of geopolymer mortar using fly ash and natural zeolite as a binder.The fly ash was replaced by natural zeolite at the rate 0, 60, 80, and 100% by weight. Sodium silicate(Na₂SiO₃) and sodium hydroxide (NaOH) solutions were mixed together and then used as a liquid portionin the mixture in order to activate the geopolymerization. The ratios between Na₂SiO₃ and NaOH werevaried, namely, 0.5, 1.0, 1.5, 2.0, and 2.5 by weight whereas the liquid/binder ratios of 0.40, 0.50, 0.60, and0.70 by weight were used. In addition, the NaOH concentrations of 5M, 10M, 15M, and 20M were alsoused as variables. Each mixture was separated and cured in the oven at the temperature of 75^oC for 24 h.Flowability and setting times of all fresh geopolymer mortars were investigated. Additional, the compressivestrength was tested at the ages of 7, 14, 28, and 60 days.

The results revealed that the mixture having Na₂SiO₃/NaOH of 1.5-2.0, 15M of NaOH concentrationand 75^oC of curing temperature, showed a compressive strength ranged between 240-940 ksc which highenough for using as normal and high strength concretes. Additionally, the compressive strength of geopolymermortar obviously increased at early age. However, at the later age, it slightly increased or did not increaseat all for some mixtures. Furthermore, the replacement of natural zeolite at the rate of 60% by weight werewell-suited for both compressive strength and workability.

Keywords : Geopolymer / Flow test / Setting times / Compressive strength / Natural zeolite