Multi-response optimization using Taguchi-Grey relational analysis for composition of fly ash-ground granulated blast furnace slag based geopolymer concrete

Abstract

In this study, Taguchi-Grey relational analysis was used to investigate and optimize the effect of ground granulated blast furnace slag (GGBS) replacement, water to geopolymer solids (W/GPS) ratio, molarity of NaOH solution, binder content and Na2SiO3 to NaOH solution ratio on setting time, workability and compressive strength of fly ash - GGBS based geopolymer concrete (GPC). After arriving at the optimal combination of mix parameters, verification experiments were conducted on the proposed optimized GPC mix with respect to fresh (setting time and workability) and hardened (compressive strength, flexural strength and splitting tensile strength) properties. The microstructural studies on selected fly ash-GGBS based GPC mixes at each GGBS replacement level and the proposed optimized GPC mix were conducted through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Field emission scanning electron microscopy (FESEM) analyses. The obtained results showed that GGBS replacement had dominant effect on setting time and compressive strength whereas W/GPS ratio significantly influenced workability of GPC. Variations in formations of N-(C)-A-S-H and C-S-H gels in GPC were confirmed from the results of microstructure analyses. The obtained results of the verification experiment on the proposed optimized GPC mix confirmed the effectiveness of Taguchi-GRA approach for determining the optimal combination of mix parameters for the production of geopolymer concrete.