Investigation of early compressive strength of fly ash-based geopolymer concrete

Development of sustainable construction materials has been the focus of research efforts worldwide in recent years. Concrete is a major construction material; hence, finding alternatives to ordinary Portland cement is of extreme importance due to high levels of carbon dioxide emissions associated with its manufacturing process. This study investigates the effects of activating solution type, curing procedure, and source of fly ash in relation to the resulting compressive strength of fly ash-based geopolymer concrete. The fly ash-based geopolymer paste microstructure was observed and density, absorption and voids were measured. Two activating solutions were used: a) a mixture of sodium hydroxide, silica fume, and water; and b) a mixture of sodium hydroxide solution, sodium silicate, and water. Test results indicate that the resulting concrete has the potential for high compressive strength and the compressive strength is directly affected by the source of fly ash. Results further indicate that compressive strength is not significantly affected by the curing condition when silica fume is used in the activating solution in comparison to the use of sodium silicate.