The urgent need to reduce the environmental footprint of concrete production has intensified research into sustainable alternatives to ordinary Portland cement (OPC) and ways to utilize industrial waste. This study is motivated by the need to enhance both the mechanical properties and durability of high volume fly ash (HVFA) concrete, by incorporating waste glass powder (GP) as a partial replacement for fly ash, with a particular focus on improving resistance to external sulfate attack. The cementitious binder of the reference mixture was a blend of 50% (OPC) and 50% fly ash by weight. Another two mixes were prepared by substituting 10% and 20% of fly ash weight with glass powder (GP). Key properties evaluated included compressive strength, water absorption, ultrasonic pulse velocity (UPV), and external sulfate resistance. Compressive strength was assessed for each mixture after 150 days of curing in both a 5% sodium sulfate (Na₂SO₄) solution and in normal water. The durability index was calculated as the difference in compressive strength between the sulfate-exposed and water-cured specimens. The results demonstrated that the inclusion of 10% and 20% glass powder in HVFA concrete present higher strength (43.6, 38.6 MPa) at both curing method in compare with reference mix (34.9 MPa). Therefore, the durability index of mixes with GP was improved, whereas 10% of GP is the optimum replacement level. The results of water absorption will decline from 3.15% to 2.33% and 2.65%, while (UPV) will increase from 4.683 Km/sec to 5.292 and 5.023 Km/sec of 10%GP and 20%GP mixtures, respectively. Significantly, UPV measurements increased by 13% and 7.2% for concrete mixes containing 10% and 20% GP, respectively, compared to the control mix, further confirming enhanced concrete uniformity and quality.
