Geopolymer Cements from Slag, Fly Ash and Silica Fume Activated with Sodium Hydroxide and Water Glass

Three different types of geopolymer cement from granulated blast furnace slag (GBFS), pulverized fly ash (FA) and silisa fume (SF) were prepared. The cements were activated by sodium hydroxide (SH) and water glass (WG) which were dissolved in mixing water. The hydration characteristics of the different cement mixes were measured including water of consistency (W/C) ratio, setting times, bulk density, apparent porosity, bound water content and compressive strength. The W/C ratio increased as the amount of NaOH increased. It also increased with addition of either FA or SF. The bound water content of the alkali-activated GBFS cement pastes gradually increased at all hydration times. The bulk density improved whilst apparent porosity declined. This had a positive effect on compressive strength. The results demonstrated that 90% GBFS and 10% Silica Fume activated by 1.0 mol/kg water glass and 3.0 M NaOH had reasonable and satisfactory hydration properties and was the most appropriate binding material. It is a sustainable binding material that can be successfully used as an alternative to ordinary Portland cement.