Effects of activator on compressive strength of fly ash-based geopolymers

The effects of different activators on compressive strength of fly ash-based geopolymers were studied. It is shown that the activative effect of NaOH and KOH solution with different concentration is weak, the compressive strength of fly ash-based geopolymers is low, but the activative effect intensifies when NaOH or KOH solution mixes with K2SiO3 solution, and the compressive strength improves too. The K2SiO3 solution shows the best activative effect, the compressive strength of fly ash-based geopolymers increases with increasing concentration of K2SiO3 solution. When the solution concentration is 2 mol/L, the 28 d compressive strength reaches the maximum, then it decreases with the increase of the solution concentration. It is guessed that geopolymerization is a stoichiometric reaction.