Characterization and Effects of Impurities on Carbonate Quantification in Heterogenous Matrices

Mineral carbonation simulates a natural weathering phenomena by breaking down silicates and oxides to form Ca & Mg carbonates. Various mineralization methods have been demonstrated as a potential technique to improve the quality of slags and tailings through neutralization and stabilization of problematic species to yield a product better suited for use in concrete. This study aims to characterize, quantify and analyze carbonates in various carbonated products such as mineralized CaCO3, CO2 mineralized Steel Slags and Mine Tailings. More than 10 samples were analyzed for carbonate measurement and verification from industrial and academic partners that pioneer commercial CO2 mineralization technologies. The samples were characterized primarily by using X-ray diffraction (XRD), Thermogravimetric Analyses (TGA), and Scanning Electron Microscopy (SEM) to gain insights into CaCO3 content. A baseline characterization of lab-grade CaCO3 and MgCO3 also revealed important considerations for CaCO3 measurement using TGA alone. The experiments using synthetic lab-grade samples also revealed that the presence of MgCO3/MgO can accelerate the decomposition of CaCO3 and thus can affect measurement parameters. Lab-grade CaCO3 samples dosed into steel slag and mine tailing also showed significant deviation in their decomposition behavior. These insights are used to inform the development of a standardized protocol for the measurement and verification of carbonate-bearing products.