Development of carbon sequestration cement-based materials with mechanochemically carbonated carbide slag

Abstract

Calcium carbide slag (CS) is a highly alkaline industrial byproduct with elevated calcium content. While CS demonstrates significant carbon sequestration potential, the inherent inertness of its carbonation product (calcite) limits its practical application in cement-based materials. In the present work, CS was mechanochemically treated with wet-grinding carbonation method. This approach achieved high-efficiency carbonation while overcoming the activity limitations of calcite product. Wet-grinding carbonation achieved 91.9 % of theoretical CO2 uptake within 15 min, reducing carbonation time by 25 % compared to conventional bubbling carbonation method, under equivalent carbonation degree. Mechanochemical forces activated the carbonated CS by stripping inert CaCO3 surface layers and exposing active sites, This process changed the inert characteristics of the calcite product, resulting in higher reactivity compared to the bubbling-carbonated CS. In addition, mechanochemical carbonation significantly reduces the particle size of CS, endowing it with dual effects of hydration induction and micro-filling. With incorporation of mechanochemically carbonated CS, the hydration induction period was shortened by 48.9 % and the 28-day compressive strength was improved by 12 %.