Surface Durability and Mechanical Performance of Sustainable KOH-Activated Hybrid Fly Ash Mortars for Flooring Layers

Sustainable mortars for flooring require mechanical stability and surface durability against abrasion, not only compressive strength. This study evaluates potassium hydroxide (KOH)-activated hybrid fly ash mortars as candidate materials for sustainable flooring and surface wear layers. Ordinary Portland cement (OPC) was partially replaced with fly ash (FA) at OPC/FA ratios of 90/10, 80/20, and 70/30, using 4 M and 8 M KOH solutions. The experimental program included the characterization of fly ash, the alkaline solution, and fine aggregate, as well as flowability, bulk density, compressive strength, abrasion mass loss, and numerical consistency analysis. The results showed that OPC exhibited the highest strength and lowest wear; among the hybrid mortars, 90/10–8 M exhibited the highest relative performance, while 80/20–8 M provided the best balance between cement reduction, strength, and wear. The integrated mechanical–surface performance index IMS and the analytical–numerical consistency assessment enabled the formulations to be ranked using an integrated selection criterion.