Developing sustainable cement through alkali-activation of waste glass and hydrophobic modification

Alkali-activated waste glass (AAWG) offers high compressive strength (up to 90 MPa) but suffers durability issue due to its poor moisture stability. Conventional stabilization methods using lime, slag, or fly ash are constrained by carbon-intensive production, policy conflicts, or dwindling supply. This study introduces a novel hydrophobic modification strategy using polydimethylsiloxane (PDMS) and polymethylhydrosiloxane (PMHS) to improve AAWG's moisture stability and durability. Incorporating 0.4–1.2 ml/100 g precursors of PDMS/PMHS imparted durable hydrophobicity, stabilized compressive strength above 50 MPa after 28 days in 99 % relative humidity, demonstrating enhanced moisture stability. Critically, hydrophobic modification benefits long-term durability by suppressing excessive liquid infiltration, which is unaddressed by traditional stabilization methods. Life cycle assessment confirmed AAWG's lower carbon emissions than ordinary Portland cement (OPC), with PDMS/PMHS causing only marginal increases. Our approach positions AAWG as a sustainable OPC alternative for structural applications involving moist environments.