Feasibility of carbon dioxide uptake cementitious materials preparation by combining γ-C2S with red mud

Abstract

To evaluate the feasibility of preparing a carbon-capture cementitious material by combining γ-C2S with red mud (RM), the physicochemical features of bulk red mud specimens with γ-C2S content of 20%, 40%, and 60% were investigated after carbonation curing. The carbonation mechanism was analyzed using x-ray diffraction (XRD), thermogravimetric-differential scanning calorimetric analysis (TG-DSC), mercury-pressure porosimetry (MIP), and scanning electron microscopy (SEM) techniques. The results show that the compressive strength of RM specimens containing 60% γ-C2S carbonized for 28 d can be increased by 180% compared with hydrated samples. The introduction of γ-C2S promotes the transformation of the carbonation products aragonite and vaterite to calcite, which is able to fill the pores, resulting in a decrease in the porosity of the samples and an increase in the strength. In addition, the expected CO2 uptake ability of RM powder is higher than the experimental results due to the precipitation of calcite on the surface of γ-C2S to form a dense layer, which hinders the dissolution of calcium ions and further diffusion of CO2 inside. A conceptual model is proposed to explore the mechanism of the influence of γ-C2S on the performance of RM. Such a study provides an alternative solution for the RM recycling and zero carbon cementitious material preparation.