Egyptian feldspar for multidimensional performance boosts in alkali-activated slag concrete

Abstract The environmental impact of conventional concrete underscores the urgent need for sustainable alternatives. Alkali-activated slag (AAS) concrete offers a lower-carbon solution, Yet its performance remains open to optimization. This study evaluates the mechanical and durability enhancements achieved by partially substituting slag with 10–50% locally available feldspar powder. The optimal replacement level of 10% is shown to provide a synergistic performance enhancement, not only improving flexural strength (24.58% at 7 days) but also, for the first time, demonstrating a significant reduction in abrasion wear (10.33%), a 15.5% improvement in water permeability, and a crucial mitigation of drying shrinkage. These findings move beyond simple strength optimization to validate 10% feldspar as a strategic additive for producing a holistically durable and serviceable AAS concrete. Microstructural evidence attributes these gains to feldspar’s role in refining pore structure and promoting the development of a dense, chemically complex sodium aluminosilicate hydrate (N-A-S-H) binder matrix. Beyond 10%, performance declines due to porosity increase and incomplete reaction. These findings support feldspar’s viability as a strategic additive in AAS concrete, aligning with global efforts to decarbonize construction.