Effect of Various Alkaline Activator Solutions on Compressive Strength of Fly Ash-Based Geopolymer Concrete

In recent years, geopolymers, as a new class of green cement binders, have been considered as an environmental-friendly alternative to Ordinary Portland Cement (OPC) which can potentially reduce negative environmental impacts of OPC effectively. In this experimental research, effects of different alkaline activator solutions and variations of associated parameters, including KOH concentration and Na2SiO3/KOH weight ratio, on the compressive strength of fly ash-based geopolymer concrete were investigated. The obtained results showed that using NaOH provided greater 3- and 7- day compressive strengths as well as faster hardening. Conversely, using KOH resulted in higher 28-day compressive strength. Additionally, simultaneous inclusion of 50% NaOH and 50% KOH resulted in decline of the compressive strength. Furthermore, the obtained results indicated that increasing the KOH concentration up to 14 M resulted in the highest compressive strength, while weight ratio of 1.5 for Na2SiO3/KOH was the optimum value to achieve highest 7-and 28-day compressive strengths.