The decomposition and quantification of carbonates in cementitious materials by thermogravimetric analysis and mass spectrometry

Carbon mineralization is a scalable technology of CO 2 abatement in the construction industry. Quantifying carbon storage is important for carbon accounting and technology development. Understanding the chemistry of carbonate-containing cementitious systems is of significant interest and requires rigorous phase identification and carbon quantification. This study establishes an integrated thermogravimetric-mass spectrometric (TG-MS) framework for identifying and quantifying various carbonates in cementitious materials. MS is complementary to TG, which alone cannot differentiate dehydration and decarbonation in multi-step decompositions of hydrated magnesium carbonates (HMCs). Systematic TG-MS measurements suggest that decomposition temperatures of CaCO 3 polymorphs, dolomite, and HMCs are primarily influenced by sample weight and heating rate, while N 2 purge rate exhibits minimal influence. Particle size strongly affects the early dehydration of HMCs. High-resolution TG sharpens derivative thermogravimetric peaks, thereby enhancing the separation of overlapping thermal events, e.g., the two-step dolomite decarbonation. Among HMCs (nesquehonite, artinite, hydromagnesite, and dypingite), only dypingite exhibits a low-temperature transition to hydromagnesite, which alters its thermal signature. CaF 2 and CaCl 2 incorporation each promotes eutectic-assisted multi-step calcite decarbonation, complicating phase identification and carbon quantification. Instrument types and crucible configurations affect thermal diffusion and gas release, therefore altering thermal signatures of carbonates. The influence of pre-test air exposure of reactive oxides and hydroxides using multi-position autosamplers on carbon quantification is evaluated. The resulting reference ranges of onset and peak temperature provide practical guidance for improving TG-based and TG-MS-based carbon quantification in cement and concrete research.