Influence of Curing on the Properties of Geopolymer Mortar Made with Low Molarity Sodium Hydroxide

Abstract

In recent years, researchers have focused on finding an alternative to ordinary Portland cement (OPC) to reduce carbon footprint. One such alternative is identified to be geopolymer which often consists of fly ash, sodium silicate, and sodium or potassium hydroxide (NaOH or KOH). Although measured strength is suitable for infrastructure application, the high molarity of NaOH creates the hazardous working environment. Therefore, the focus of this study was to evaluate the feasibility of using low molarity (4 M) sodium hydroxide in geopolymer mortar. The conventional compressive and tensile strength tests along with nondestructive (free–free resonant column) tests were performed to identify the influence of curing regime on the gain in strength and moduli of low molarity geopolymer. The strength and moduli evaluation suggested that geopolymer of sufficient strength can be produced using low molar NaOH. The strength and moduli increased with increase in curing temperature or curing time or both. However, extended curing at higher temperature inversely influenced strength and moduli. More research is needed to optimize curing regime and identify long-term durability of geopolymer produced with low molar NaOH.