Impact of synthesis parameters on the mechanical properties of metakaolin – based geopolymer concrete

Abstract

Geopolymer concretes have emerged from various research endeavours as promising alternative to conventional Portland cement concrete, but the conflicting findings in relation to the influence of synthesis parameters pose a serious challenge to practical application of geopolymer concrete.  This study investigated the impact of synthesis parameters on the compressive strength of metakaolin – based geopolymer concrete. The main objective is to analyse the influence of varying synthesis parameters such as alkaline activator concentrations (SH molarity), activator ratio (sodium silicate/sodium hydroxide solution) and activator/metakaolin (A/M) ratio on the compressive strength property of metakaolin based geopolymer concrete. The synthesis parameters were considered under three trial levels and were distributed using Taguchi’s orthogonal array distribution. The results of the compressive strengths were analysed using the signal to noise ratio (SNR) and the analysis of variance (ANOVA). The analysis indicates that the contribution of each synthesis parameter to the compressive strength of geopolymer concrete differs for 3day, 7day and 28day. It was found that A/M ratio recorded the highest contribution of 56.3%, 42.8% and 41.5% to the strength development of geopolymer concrete at 3, 7 and 28 day The impact of these synthesis parameters was confirmed by conducing confirmation test and prediction error of +2.84, +0.52 and -1.51 were obtained for 3, 7 and 28day strength. It was concluded that the quality of metakaolin – based geopolymer concrete can be controlled with the controlled quantity of its synthesis constituents, and Taguchi method proved to be a suitable tool for optimizing geopolymer concrete mix.