Accelerated wet carbonation of recycled cement powder using alkanolamines for enhancing early-age hydration and strength as supplementary cementitious materials

Wet carbonation of calcium-rich solid wastes to produce Supplementary Cementitious Materials (SCMs) has gained research attention. This study investigates a capture-mineralization approach using monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) to enhance carbonation of recycled cement powder (RCP). The novelty lies in exploiting the dual alkalinity and complexation capability of alkanolamines to overcome the kinetic bottlenecks of CO2 transport and Ca2+ leaching. Results show alkanolamine solutions significantly accelerate carbonation, achieving a final degree of 64.8% within 60 min, compared to 56.4% with pure water. At 10 min, DEA reached 57.2%, versus 39.3% conventionally. The hydration induction period of cement mortars incorporating modified RCP was shortened by 1.2–2.4 h, with DEA exhibiting the most pronounced catalytic effect, attributed to calcite nucleation sites and reactive silica gel. This modified RCP accelerates early-age hydration and enhances early strength compared to untreated RCP, offering a viable sustainable option for cement replacement.