Influence of Relative Humidity on Compressive Strength of Low-Calcium Fly Ash Geopolymer During Heat Curing

Abstract Compare to ordinary Portland cement, Geopolymers are more environmentally friendly materials. They have some remarkable advantages such as resistance against fire and acid. Low-calcium fly ash-based geopolymers are heat cured in ovens and incubators where they are exposed to different temperatures and relative humidity (RH). The influence of the temperature on the alkali-activated materials (AAM) and geopolymers are well studied and understood. But there is a lack of enough information regarding the effect of RH during heat curing on the properties of the materials. This research aimed to study the influence of RH on the compressive strength of the geopolymer. Low-calcium fly ash-based geopolymer was cured at 45 °C. The effect of around 10% and 94% RH was studied on 7-, 28- and 56- day compressive strength of the materials. It was found that RH has a negative influence on the early age strength of the mortars. More studies are required to find the influence of RH on other properties of the geopolymer.