Multi-response optimization of flowability and compressive strength in alkali-activated slag mortar using Taguchi–PCR-TOPSIS approach.

Abstract

This study aimed to identify an Alkali-Activated Slag (AAS) mortar mixture balancing flowability and compressive strength as a sustainable alternative to Portland cement. Twenty-seven mixtures varying activator dosage, modulus, water-to-binder ratio, aggregate-to-binder ratio, and superplasticizer content were evaluated using a Taguchi L27 design, ANOVA, and PCR-TOPSIS optimization. Activator dosage was most influential (70.90% contribution), followed by aggregate-to-binder ratio (10.12%), while modulus and water-to-binder ratio played minor roles. The optimal mixture (flow 115%, strength 48.85 MPa) was validated by an independent replicate batch, with an estimated 79% lower CO2 footprint than a Portland-cement control. Reaction mechanisms were not confirmed microstructurally. Unlike prior single-response approaches, this study combines statistical validation, experimental confirmation, and environmental estimation for a more rigorous mortar design basis.