Effect of Lime Stone Dust on Geopolymerisation and Geopolymeric Structure

In this paper, synthesis of geopolymer from fly ash with sodium hydroxide as activator was studied. Fly ash was replaced by Lime stone dust in various proportions (10% and 15%) where Fly ash was used as source material for synthesis of geopolymer. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions were mixed maintaining a silicate modulus (Na2O / SiO2) at 1. Scanning electron microscopy (SEM), mercury intrusion porosimetry was carried out to characterize the geopolymer specimens. Compressive strength and water absorption were also tested on geopolymer pastes. The results illustrate that high strength geopolymer pastes can be produced using mixture of fly ash with Lime stone dust in lower curing temperature. The compressive strength of geopolymer paste specimens with 15% Lime stone dust were increased about 44% when cured for 48 hours at 65 O C. Specimens incorporated with Lime stone dust showed better microstructure and exhibited lesser porosity. The average pore diameters get reduced due to the addition of Lime stone dust which has a favourable effect on geopolymer structure as building material. Keywords— Geopolymer, Sodium Silicate, Fly ash, Lime stone dust, ESEM, MIP.