Effect of Low NaOH Concentration on Compressive Strength and Products of High Calcium Geopolymer

doi: 10.14456/mijet.2016.3

Abstract

This research aims to study effect of low NaOH concentration on compressive strength and products of high calcium geopolymer. Fly ash was used to be starting material to synthesize geopolymer and mixed with 2 M sodium hydroxide (NaOH) concentrations. Silica fume was also used to be addition of silica in mixture to make different Si/Al ratios. Geopolymer pastes were determined compressive strength at the ages of 7, 14 and 28 days. The products of geopolymer pastes were characterized by Fourier transform infrared spectroscopy (FTIR) and salicylic acid with methanol (SAM solution) leaching test. The products of geopolymer were determined by the FTIR in different patterns before and after SAM solution leaching which is specific for calcium composite gel. It was found that low NaOH solution can produce the highest compressive strength of 15.91 MPa at the age of 28 days. The products of high calcium geopolymer were possible be calcium silicate hydrate (CSH gel), calcium aluminate silicate hydrate (CASH gel), geopolymer (NASH gel) and zeolite which were characterized by FTIR and SAM leaching tests.