Measuring mineralized carbon in carbonate minerals and cementitious materials by an acid digestion-titration method

Abstract

As carbon dioxide (CO₂) sequestration technology begins to emerge in the construction and building materials sectors, industry stakeholders require quantifiable assurance mineralized CO₂ content of emerging carbonated products. This study adapts a Digestion-Titration Method (DTM) for the determination of mineralized CO₂ content in cementitious materials based on tests that were originally developed in the early 1900s. The experimental conditions were optimized with a systematic design of experiments (DOE) approach. The method utilizes hydrochloric acid to digest carbonate minerals (i.e., CaCO₃, MgCO₃) under vacuum conditions. The liberated CO₂ from acid digestion is captured by a barium hydroxide solution to precipitate barium carbonate. Titration is used to quantify the remaining barium hydroxide, yielding a back-estimation of the total CO₂ content. Mixtures of fixed compositions, portland cement, and a carbonated cementitious commercial product were employed to validate the proposed DTM method. DTM results were compared to thermogravimetric analysis (TGA) of the same samples. The outcomes of this work demonstrate that DTM can provide results consistent with TGA for samples containing a singular carbonate phase and yield more consistent quantification of mineralized CO₂ for samples containing multiple phases.