Optimization of Ambient-Cured, Alkali-Activated One-Part Green Mortar with Industrial Waste Using the Taguchi & Taguchi- Grey relational Method

This study develops a novel one-part alkali-activated mortar (AAOPM) synthesized at room temperature, incorporating nano-silica, using industrial waste-fly ash (FA) and ground granulated blast-furnace slag (GGBFS) as precursors, and anhydrous sodium metasilicate (Na₂SiO₃) as the solid activator. Unlike conventional two-part systems reliant on liquid alkalis, this ready-to-use formulation improves on-site practicality and safety. Optimal mix designs were derived via Taguchi combined with Taguchi-Grey Relational Analysis (TGRA) using an L₉ orthogonal array. Four factors at three levels were assessed: FA/GGBFS ratio (F/S 1–2.33), water/binder ratio(W/B 0.4–0.5), activator dosage(SMS 8–12%), and nano-silica content(NS 1–2%). Multi-response outputs comprised fresh properties(flow, setting time) and mechanical properties(compressive, flexural strength at 28 days), which were analysed using Minitab software. The significance of the factors was confirmed through analysis of variance, and the strongest effects of the factors were demonstrated on strength responses by NS content and the F/S ratio, and flow and setting time by W/B. TGRA validation determined the best conditions (F/S 1:1, W/B 0.5, 8% activator, 2% NS) with a compressive strength of 50 MPa and flexural strength of 6.5 MPa far greater than most reported AAOPMs. Microstructural studies demonstrated thick C/N-(A)-S-H gels, compact morphology, and high thermal stability characterization.