Mechanical properties of geopolymer mortar made with class F fly ash and class C fly
ash are evaluated and compared in this paper. Fly ashes were activated with a combined
NaOH and Na2SiO3 alkali solution, and their strength development was observed during
one year. It was observed that compressive strength values were between 10.22 and
15.83 MPa for geopolymer mortar mixtures made with class C fly ash. The values of up
to 56.44 MPa were obtained for geopolymer made with class F fly ash.