Effect of wet grinding carbonation of sintering red mud on the performance of carbon sequestered mortar

Abstract

The use of alkaline solid waste to CO2 capture is a potential way to upgrade the recycling of solid waste and reduce CO2 emission. In previous work, we proposed a novel wet grinding carbonation technique to achieve rapid carbonation of sintering red mud (SRM). Herein, the effect of wet grinding carbonation of SRM (WGCS) replacement rate (0 %, 5 %, 10 %, 15 %, 20 % and 25 %) on the hydration and hardening of Portland cement was further explored, such as rheology, compressive strength, hydration products and water transfer properties. The plastic viscosity and yield stress of carbon sequestered paste rose together with the WGCS replacement rate, which was due to the decreased D50 of SRM after wet grinding carbonation. When the WGCS replacement rate was 15 %, the 56 d compressive strength of carbon sequestered mortar was increased by 14.1 %. The microscopic characterization showed that the nucleation of calcite crystals and the pozzolanic reaction of silica-rich gels clearly improved the microstructure compactness. The electric flux and porosity of cement mortar was decreased by 25.7 % and 11.4 %, respectively. In terms of environmental and economic benefits, the CO2 sequestration of carbon sequestered mortar reached as high as 24.7 kg/m3 and the CO2 emission was reduced by 30.9 %.