Study of geopolymer mortar based on alkali-activated green tuff and slag with optimal NaOH and curing temperature

The utilization of alkali-activated green tuff to produce geopolymer mortar, using low molarity NaOH and curing temperature to reduce energy consumption is a key focus of this research. This article examines physical and chemical analyses of geopolymer mortar based on alkali-activated green tuff at different ages (7 to 180) under ambient temperature conditions (26 ± 3℃) The alkaline activators in the mortar consist of sodium hydroxide with two different molarities (4 and 6), and sodium silicate. Analytical results indicate that higher molarity leads to the generation of more cations in the ionic soup. In the short term, this accelerates geopolymer formation and enhances compressive strength; however, in the long run, it results in increased shrinkage and dimensional instability, leading to the development of cracks. The findings reveal that the compressive strength of the mortar containing alkali-activated green tuff with 4M NaOH(aq) at 180 days is approximately 58% higher than that of mortar containing Portland cement. XRD analysis further demonstrates that the predominant phases formed in the mortar with alkali-activated green tuff are C-A-S-H and N-A-S-H gels. The higher presence of C-A-S-H gel is attributed to the inclusion of slag, constituting half of the alkali-activated binder.