<p>This study investigates the sulfate durability performance of concrete incorporating lead–zinc tailings sand (LZTS) as partial replacement for fine aggregates. Greater emphasis is placed on long-term resistance to sulfate attack rather than on strength enhancement, ensuring full consistency with the manuscript title. Sulfate exposure conducted in a 5% Na₂SO₄ solution for periods of up to 180&#xa0;days, during which mass change, linear expansion, surface degradation, and residual mechanical strength were systematically evaluated. The results demonstrate that optimized levels of LZTS replacement, in combination with low-dosage hybrid nanomaterials, significantly enhance the sulfate resistance while maintaining satisfactory mechanical performance. From a sustainability perspective, replacement of up to 50% of natural river sand is achievable, contributing to reduced depletion of natural resources. Microstructural observations obtained from SEM, supported by XRD and FTIR analyses, provide indirect yet consistent evidence of matrix densification and suppression of sulfate reaction products. FTIR spectra confirmed these observations by intensifying Si–O–Si and Al–O–Si bands and weakening Sulfate-associated vibrations with Heavy metal immobilization efficiency exceeding 90%. The findings reveal the potential of LZTS-based concrete as a durable and environmentally responsible construction material for sulfate-rich environments.</p>