NaOH-activated ground fly ash geopolymer cured at ambient temperature

► Sodium hydroxide-activated ground fly ash cured at room temperature can be produced with reasonable strength. ► A 28 day compressive strength of 20.0 - 23.0 MPa was obtained with NaOH concentration in the range 9.5-14.0 M. ► Ground fine high calcium fly ash can be used as a source material for making geopolymers cured at ambient temperature.