Degradation behavior and mechanism of recycled glass powder–cement binders under sulfuric acid attack

Recycled glass powder (GP) is a Si-rich, low-carbon supplementary cementitious material (SCM) that can reduce cement demand and carbon emissions. It may also improve the corrosion resistance of cement owing to its intrinsic acid stability and its ability to tailor hydrate chemistry. However, the durability of GP–cement binders under sulfuric acid attack relevant to sewer systems remains insufficiently understood, particularly the coupling between surface corrosion-layer evolution and internal acid-induced degradation. Here, Portland cement binders with 0–50% GP replacement were exposed to sulfuric acid (pH 1.0–1.9) for 75 d. Degradation performance and mechanisms were elucidated by integrating dimensional changes, degradation/infiltration depths, ionic leaching–infiltration, phase assemblage, and microstructural evolution. GP incorporation markedly reduced the apparent expansion by up to 38.4%, primarily attributed to a 31.3%–64.9% reduction in portlandite and the formation of C–(N)–S–H phases with lower Ca/Si ratios in the original binders, which limited leachable Ca^{2 +}. Consequently, the corrosion layers exhibited improved structural integrity, with 10.9%–25.7% less gypsum formation and more continuous silica gel networks. However, the reduction in leachable OH^– by 13.8%–51.7% due to the cement dilution and the pozzolanic reaction of GP facilitated deeper acid infiltration and greater Al³⁺ leaching. Overall, a dual effect of GP–cement binders was found: enhanced surface stability but slightly accelerated internal degradation. A 25% GP replacement provided a better balance, achieving superior sulfuric-acid resistance. These findings provide guidance for designing lower-carbon cementitious materials using upcycled Si-rich waste streams for aggressive service environments.