Influence of alkaline activators on the mechanical properties of fly ash based geopolymer concrete cured at ambient temperature

In this study, cement-free geopolymer concrete (GPC) mixes are prepared using locally produced fly ash with varying NaOH concentrations (8 M−16 M), Na2SiO3/NaOH ratios (1.5–2.5) and alkaline activator to fly ash (AA/FA) ratios (0.4–0.6) to investigate the influence of alkaline activators on the mechanical properties of GPC cured at ambient temperatures. The optimum compressive strength (21.5 MPa) of ambient-cured GPC was attained with NaOH concentration of 14 M, Na2SiO3/NaOH of 1.5 and AA/FA of 0.5. The optimum flexural strength (5 MPa) of ambient-cured GPC was attained with NaOH concentration of 16 M, Na2SiO3/NaOH of 1.5 and AA/FA of 0.5.