Investigate the effects of molarity on the strength of geopolymers

Abstract

Compressive strength results of class-f fly ash geopolymer (no aggregates or admixtures) cured in water are reported. Na2SiO3 was mixed with NaOH at mass ratio of 2.5: 1, while the mass ratio of fly-ash to alkaline activator is kept at 3:1 for the geopolymer mix design. The effects of varying different molarity of NaOH and mixing time on fly ash geopolymer’s compressive strength was examined. Compressive strength of water-cured geopolymer samples was found to increase with molarity of NaOH and increased mixing time did not significantly impact the overall strength of geopolymer. Water curing has also been attested as the more inefficient curing method for geopolymers when compared to ambient curing in terms of 28th-day compressive strength. Peak compressive strength of approximately 50MPa was obtained for water-cured geopolymer at high NaOH molarity (15M, 18M).