Abstract
This study quantified CO2 in various concrete binders and aggregates using back titration, thermogravimetric analysis (TG-DTA), and the combustion-infrared absorption method, and examined the consistency among these methods along with error factors related to material characteristics. Back titration is considered the most appropriate method for both binders and aggregates because that directly measures CO2, though sulfides pose a potential issue. In contrast, the TG-DTA method may underestimate or overestimate CO2 due to the oxidation of sulfides in blast furnace slag, combustion of unburned carbon in fly ash, and dehydration of clay minerals in aggregates, which coincide with the temperature range for decomposition of calcium carbonate. The combustion-infrared absorption method may also produce inaccurate CO2 values, as elemental or organic carbon within the aggregate particles can lead to overestimation or underestimation. In blended cement, sulfur compounds may interfere with infrared absorption, further skewing the CO2 measurement. From these findings, back titration was identified as the most reliable method for CO2 quantification in concrete materials. Understanding the specific characteristics of each sample and selecting the appropriate method is crucial for accurate CO2 analysis in concrete materials and concrete structures.
