Optimizing the Performance of Geopolymer Mortar Based on Flowability, Strength, and Durability Properties

Abstract

Abstract This study presents the application of Taguchi-grey relational analysis (GRA) to investigate the effect of control parameters on flowability, compressive strength, and sulfate and acid resistance of geopolymer mortar (GPM) simultaneously. The control parameters selected were ground granulated blast-furnace slag (GGBS) replacement (15 %, 30 %, and 45 %), water-to-geopolymer solids (W/GPS) ratio (0.31, 0.33, and 0.35), molarity of sodium hydroxide (NaOH) solution (10 M, 12 M, and 14 M), and sand-to-binder (S/B) ratio (1.5, 2, and 2.5). From the obtained results, GGBS replacement and the S/B ratio significantly influenced most of the studied properties of GPM. GPM prepared with a higher GGBS replacement showed higher compressive strength under ambient conditions, whereas GPM prepared with a lower GGBS replacement exhibited improved resistance against sulfate and acid attacks. From results of multiresponse optimization by Taguchi-GRA, GPM made with higher level of GGBS replacement (45 %) and molarity of NaOH solution (14 M), medium level of S/B ratio (2), and lower level of W/GPS ratio (0.31) exhibited better performance in most of studied properties simultaneously. Variations in peak intensity of compounds related to N-A-S-H and N-(C)-A-S-H gels formed in GPM were consistent with variations in compressive strength with ambient curing age as well as with variations in compressive strength of GPM exposed to sulfate solutions. Furthermore, a significant decrease in peak intensity of compounds related to aluminosilicate gels and in atomic Na/Si ratio and Al/Si ratio are in line with significant reduction in compressive strength of GPM when exposed to acid solutions that substantiate depolymerization of aluminosilicate gels in acidic environments.