Application of acid digestion-based total inorganic carbon measurement for carbonated cement-based materials

There is growing societal demand for methods to quantify the amount of CO₂ immobilized in cement-based materials. In this study, we compared and evaluated multiple analytical approaches: two different interpretation methods applied to thermogravimetric analysis (TGA) data conventionally used in this field, and two techniques widely adopted in soil science and related areas. The first of these involves heating the sample to release CO₂, which is then quantified using infrared absorption spectroscopy; the second involves dissolving carbonates in the sample using acid, with the evolved CO₂ gas similarly measured using infrared absorption. In carbonated cement pastes, when silica gel and carbonates are in close contact, CO₂ may be released at relatively low temperatures. This temperature range overlaps that of organic matter decomposition, which can complicate quantitative analyses using thermal methods. However, accurate quantification is feasible in systems with minimal organic content. During acid decomposition, silica gel may interfere with carbonate dissolution. Nevertheless, if the sample is sufficiently ground, an appropriate volume of the acid solution is used, and the dissolution time is properly managed under stirring conditions, this method offers a simple and practical means for CO₂ quantification. • An acid dissolution coupled NDIR-based TIC measurement is proposed for CO 2 quantification. • AD-TIC results are nearly equivalent to those from the standardized method (DIN19539). • TGA-based methods underestimate CO 2 content compared to NDIR spectroscopy. • AD-TIC method provides accurate CO 2 quantification in ∼20 min with a simple procedure.