Real-time measurement and reaction rate analysis of CO2 absorption in cementitious materials by gas pressure monitoring using a batch reactor

CO 2 -absorbing concrete is being actively researched toward carbon neutrality. Real-time measurement of CO 2 absorption is essential to accurately assess the progress of the carbonation reaction, elucidate the carbonation mechanism through reaction rate analysis, and optimize the carbonation conditions. In this study, a batch reactor was developed for real-time measurement of CO 2 absorption in cementitious materials. A reaction tube and a CO 2 container were placed in a constant-temperature oven and connected using a valve to initiate the carbonation reaction. The amount and rate of CO 2 absorption were measured by monitoring the gas pressure with a time resolution of minutes, after correcting for the influence of water evaporation on pressure. The γ-2CaO·SiO 2 powder absorbed 103 g CO2 /kg solid of CO 2 , achieving 21 % of its theoretical capacity within 5 min. A comparison between the CO 2 absorption values determined by gas pressure monitoring and destructive analysis of carbonated samples revealed that the ratio remained stable for different materials and carbonation conditions, with an average of 1.00 and a standard deviation of 0.07. Additionally, 93 % of the data points were in the range of 0.90–1.10, demonstrating high reliability of the proposed method. Therefore, this method is a rapid, simple, and reliable means of evaluating CO 2 absorption for various materials and carbonation conditions. Furthermore, this method can be combined with sample analysis to better understand the carbonation mechanism in CO 2 -absorbing concrete and determine optimal carbonation conditions. • A real-time CO 2 absorption measurement method using a batch reactor was developed. • CO 2 absorption was quantified every minute by gas pressure change, corrected for H 2 O evaporation. • γ-C 2 S absorbed 103 g CO2 /kg solid within 5 min, demonstrating rapid carbonation. • Measured values by this method showed excellent agreement with reliable destructive analysis. • This method enables rapid and reliable CO 2 absorption assessment under various conditions.