Resistance to algae and fungi formation of high calcium fly ash geopolymer paste containing TiO2

Abstract In this paper, the resistance to algae and fungi formation on the surface of high calcium fly ash geopolymer containing nano-titanium dioxide was studied. The compressive strength and density of geopolymer paste were also reported. Sodium hydroxide (NaOH)with 10 M concentration, liquid/binder ratio (L/B) of 0.40 and sodium silicate/sodium hydroxide ratio (NS/NH) of 0.67 were used for all mixes. The fly ash was replaced by nano-titanium dioxide at 0, 1, 2, 3, 4 and 5% by weight. A moderate temperature of 40 o C for 48 h was used for the curing of pastes. The pastes containing nano-titanium dioxide showed the ability to resist the formation of algae and fungi on the surface of samples. The increasing nano-titanium dioxide content up to 5 %wt significantly increased the ability to resist algae and fungi formations on surface with only slight reductions in compressive strength and density. This indicates the suitability of using high calcium fly ash geopolymer containing nano-titanium dioxide to solve the problem of algae and fungi formation on the surface.