High calcium fly ash geopolymer containing diatomite as additive

310-318This paper studies the influence of the addition of diatomite on the properties of high calcium fly ash geopolymer pastes. Diatomite is calcined at 800°C and used to partially replace fly ash at the rate of 0, 10, 20, 30 and 40% by weight of binder. Sodium silicate (Na2SiO3), sodium hydroxide (NaOH) solution and curing at temperature of 60°C for 24 h are used to activate the geopolymerization. The NaOH concentration of 10 M and Na2SiO3/NaOH ratio of 2.0 by weight are used for all mixes. The results revealed that the use of diatomite to replace part of fly ash delayed the setting time of fresh geopolymer paste and also resulted in the reduction of density of hardened paste which is highly desirable for lightweight structure member. However, the strength and modulus of elasticity of the paste are reduced. Another positive effect is the increase in the strain capacity of the paste. The increase in strain capacity is significant and reflects in the ability of the paste to withstand increased strain before cracking