Performance of high calcium fly ash based geopolymer concrete in chloride environment

This paper presents research on geopolymer concrete performance using high calcium fly ash in a chloride environment. The experiment, since there is no specific geopolymer concrete standard up to the present, uses Ordinary Portland Cement concrete standard. Concrete used in chloride environment requires a minimum of 35 MPa concrete strength and maximum water-cement ratio of 0.4. In this study, three compositions of geopolymer concrete were prepared, namely mix-1, mix-2, and mix-3. The mixes were produced by mixing fly ash, alkaline activator, sand, gravel, and water. Sodium metasilicate granular pentahydrate and sodium hydroxide flake were used as the alkali activators. Two percent of sucrose was added to the fly ash for improving geopolymer concrete workability. Geopolymer concrete curing was performed by placing test specimens into a closed plastic box at 28-30°C room temperature for 7, 14, and 28 days. Workability tests showed that mix-3 had a slump of 227 mm, which was only slightly larger than mix-1 and mix-2. Permeability test showed that the three mixes had almost the same quality at 28 days. Based on resistivity test, mix-3 had the best performance at 7, 14, and 28 days. In term of compressive strength, mix-3 had the highest strength at 7, 14, and 28 days. Furthermore, mix-3 also had the highest pH compared with the other two mixes.