100% Waste-Derived Carbon-Sequestering Binder via Low-Temperature Sintering Enabled by Waste Glass

Traditional cement production contributes substantial CO2 emissions, prompting a need to develop alternative binders. This work aims to report the development of a fully waste-derived carbon-sequestering binder produced by sintering at a lower temperature. A C2S-based binder was successfully produced using 55% carbide slag and 45% waste glass powder, yielding 34.3 wt % β-C2S and 24.2 wt % γ-C2S at 1100 °C. The incorporation of waste glass provided a fluxing effect due to its Na2O content, enabling C2S formation at reduced temperature. The synthesized binder achieved a compressive strength of 58.6 MPa after carbonation curing for 5 h, accompanied by a CO2 uptake of 14.6%. Mineralogical and microstructural analyses revealed calcite as the dominant carbonation product with a refined pore structure and low porosity, both of which contributed to early strength development. Moreover, it was found that an excessive raw meal Ca/Si ratio (>2.2) can significantly deteriorate the microstructure and strength of a carbonated paste. Finally, the preliminary carbon footprint assessment indicated that the synthesized binder offers a potential CO2 emissions reduction of up to 60% compared to conventional Ordinary Portland Cement production. This work establishes the feasibility of producing a 100% waste-derived, low-temperature binder that actively sequesters CO2, offering an alternative to conventional cement in the transition toward carbon-neutral construction.