Carbonated Silicate Minerals and Industrial Wastes As Sustainable Construction Materials

Given that the cement industry is responsible for 7% of global CO₂ emissions, various CO₂ mitigation strategies need to be employed to reduce the overall carbon footprint of cement and building materials. One such method to reduce CO₂ emissions during the production of cement and building materials is to incorporate carbonated materials and their by-products into concrete. Since silicate minerals such as serpentine ((Mg, Fe)₃Si₂O₅(OH)₄) and olivine ((Mg,Fe)₂SiO₄) contain more than 35% of magnesium and silicon, they can be reacted with CO₂ to form carbonates and other by-products which can then be used as cementitious materials. In addition, industrial wastes such as steel slag also have a significant composition of calcium and silicon, which are key constituents in building materials. In this study, various materials are synthesized from the alkaline rich minerals such as olivine and industrial wastes such as steel slag to produce silica, magnesium carbonates, and carbonated steel slag. The synthesis of these materials is via various routes which include direct carbonation of alkaline material-CO₂-reaction fluid, and indirect carbonation which involves dissolution of the alkaline content of the mineral followed by the formation of carbonates. The composition of these materials is determined using X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Total Carbon Analysis (TCA), and Total Inorganic Carbon Analysis (TIC). Morphological features were characterized using BET pore volume distributions, particle size analyses, and Scanning Electron Microscopy (SEM). Varying amounts of these materials were then incorporated into concrete and their compressive and mechanical strengths were tested over a period of time to determine the optimal composition of these materials to achieve the highest compressive and mechanical strengths of these novel composites.