Effect of NaOH Concentration and Curing Regimes on Compressive Strength of Fly Ash-Based Geopolymer

In this study, two processing parameters in preparation of high-strength fly ash based-geopolymer: concentrations of NaOH solution and curing regimes were reexamined. From the study of NaOH solution concentration effect, a sharp rise in compressive strength to 55.7 MPa was observed when the solution concentration was increased from 4 to 6 molar (M). Further increase in the concentration up to 12 M caused the setting time of the paste to increase continuously whereas the compressive strength was slightly improved. As for the various curing regimes, the resulting compressive strength was not significantly different. The suitable curing regime was the one at 90 degrees C in the water-saturated atmosphere for 24 hours, then at room temperature in the water-saturated atmosphere for 72 hours and finally at room temperature in a dry normal atmosphere for 72 hours (90C24h-RT). (C) 2018 Elsevier Ltd. All rights reserved.