Upcycling sintering red mud waste for novel superfine composite mineral admixture and CO2 sequestration

To utilize the sintering red mud waste（SRM）on a large scale and sequester CO2, a room temperature in-situ wet carbonation method was proposed for activation of SRM. The wet carbonation reaction process of SRM was investigated, and the evolution of phase composition, microstructure and pore structure during carbonation of the SRM was revealed by XRD, TG/DTG, FT-IR, NMR, SEM and nitrogen adsorption. Moreover, the feasibility of carbonated SRM (C-SRM) as a high value-added mineral admixture was explored. The results showed that the carbonation of SRM produced a large number of fine calcite crystals and silica-alumina gel with high polymerization. After 3 h of carbonation, the SRM achieved a CO2 sequestration rate of 15.3%, calcite (Cc) yield of 86.5% and Na+ leaching rate of 81.8%. The C-SRM possessed a high pozzolanic reactivity and fine particle size, showing its potential as a cement mineral admixture.