Performance of hybrid cementitious composites with waste glass powder and recycled HDPE fibers under sodium and magnesium sulfate exposure

• GP reduced expansion under Na₂SO₄ by up to 38% compared to control • HDPE fibers lowered compressive strength but improved crack resistance • MgSO₄ caused less expansion but higher strength loss via C–S–H alteration • GP–HDPE synergy enhanced sulfate durability at optimized dosages • Novel hybrid system offers eco-friendly binder with targeted sulfate resistance This study addresses the sustainability challenges of sulfate-rich exposure conditions for cementitious composites through investigating the combined use of waste glass powder (GP) and recycled high-density polyethylene (HDPE) fibers. GP at 10% and 20% cement replacement content, and recycled HDPE fibers in the range of 1.0%, 1.5%, and 2.0% by binder volume were incorporated. The test program evaluated setting time, slump flow, compressive strength, mass change, expansion, and water absorption after up to 240 days of immersion in sodium sulfate (Na₂SO₄) and magnesium sulfate (MgSO₄). Findings demonstrate that GP increased sulfate resistance, particularly in MgSO₄, with fewer mass change and expansion. Low fiber content at dosages improved dimensional stability but over-addition (2%) favored greater permeability with greater water absorption (up to 8.3%) and ultimate strength losses (down to 8.5 MPa in Na₂SO₄ and 8.8 MPa in MgSO₄). Strong linear correlations between compressive strength and water absorption (R² up to 0.9429) and strength and mass change (R² up to 0.6293) were established, confirming permeability as a key indicator of durability. The novelty of this work is the first integrated, long-term quantification of chemical (GP) and physical (HDPE) processes under both expansive and non-expansive sulfate attacks, demonstrating performance trade-offs in hybrid composites. Based on a combined evaluation of workability, early-age strength, dimensional stability, and long-term sulfate resistance, mixtures incorporating 10% GP replacement and 1.0–1.5% recycled HDPE fiber content were identified as providing a balanced and optimal performance. The implications are that carefully optimized GP–HDPE combinations can significantly enhance sulfate resistance, while excessive fiber content may adversely affect permeability and long-term durability. Further research is required on modification of fiber–matrix interface and microstructural evolution for field scale applications under adverse sulfate conditions.