Effect of Addition of Microsilica and Nanoalumina on Compressive Strength and Products of High Calcium Fly Ash Geopolymer with Low Concentration NaOH

Abstract

This research aims to study the effect of addition of microsilica and nanoalumina on compressive strength and products of high calcium fly ash geopolymer with low NaOH concentration. Microsilica and nanoalumina were added in the mixture in order to adjust the Si/Al ratios which resulted in the change of product form of geopolymer pastes. Geopolymer was synthesized using high calcium fly ash and 2 molar sodium hydroxide (NaOH). Microsilica and/or nanoalumina were added as additional sources of silica and alumina in the mixtures. Compressive strengths of pastes were investigated at the age of 7, 28 and 60 days. The products of geopolymer pastes were characterized by FTIR and salicylic acid with methanol (SAM leaching test). The results showed that the mix (2Si10Al0) with additional 10% of microsilica gave the highest compressive strength of 14 MPa at the age of 60 days. The products of geopolymer pastes were CSH gel, CASH gel, NASH gel and zeolite which were characterized by FTIR and SAM leaching test.