Workability and Compressive Strength of Geopolymer Mortar from Fly Ash Containing Diatomite

Abstract

This article presented workability and compressive strength of fly ash based of geopolymer mortarcontaining diatomite as binder replacement at the rates of 0, 60, 80, and 100% by weight. Sodium silicate(Na2SiO3) and sodium hydroxide (NaOH) solutions were mixed together and then used as a liquid portion inthe mixture in order to activate the geopolymerization. The ratios between Na2SiO3 and NaOH were varied,namesly, 0.5, 1.0, 1.5, 2.0, and 2.5 by weight whereas the ratios between liquid binder of 0.40, 0.50, 0.60, and0.70 by weight were varied. The additional water was added to improve the workability of fresh geopolymermortar. The ratios between additional water and binder were varied, that is to say, 0, 3, 6, 9, 12, and 15%by weight. In additional, the NaOH concentration of 5M, 10M, 15M, and 20M were also used as variables.Each mixture was separated and cured in the oven at the temperature of 60oC, 75oC, and 90oC for 24 h.Flowability of all fresh geopolymer mortars were investigated and the compressive strength test was applied atthe ages of 7, 14, and 28 days.The results revealed that the mixture having Na2SiO3/NaOH of 1.5-2.5, 15M of NaOH concentration,and 75oC of curing temperature showed compressive strength between 223-939 ksc which high enough forusing as normal strength concrete. Moreover, additional water could improve the workability of freshgeopolymer mortar, however, the compressive strength reduction could be observed. Additionally,the compressive strength of geopolymer mortar increased obviously at early age, however, at the later ageit was slightly increased for some mixtures. Furthermore, the replacement of diatomite at the rate of 60 and80% by weight were well suited for both compressive strength and workability.