Influence of the activator nature on mechanical properties of fly ash-based geopolymer
Abstract : Geopolymers are included in the group of low-emission materials called "low-carbon" binders. The amount of CO₂ generated during production of the material may be reduced to only 10% of the CO₂ emitted during production of Portland cement, which explains the increasing interest of the construction industry in this type of binders. This paper presents a comparative study concerning fly ash-based geopolymers prepared with different formulations of activators. For aluminosilicate activation, most commonly available water glass mixed with sodium hydroxide pellets was used, as well as a specially developed aqueous silicate solution Geosil ®. The same molar ratio was used for both activators. Two geopolymer mortars were tested and compared in the aspect of their mechanical properties. Tests were made on geopolymer mixes based on fly ash (FA) with the addition of ground granulated blast furnace slag (GGBFS), with the additives constituting 10, 30 and 50%, respectively. The investigations enabled demonstration of the effect of different nature of activator on the mechanical performances at 2, 7 and 28 days. Test results show that both geopolymer mortars have obtained similar strengths. The use of a ready-made industrial activator facilitate the mix preparation process, and makes it safer due to the limited handling of NaOH pellets.