IMAGE-BASED EVALUATION OF CO2 UPTAKE IN MORTAR UNDER ACCELERATED CARBONATION

การประเมินการดูดซับคาร์บอนไดออกไซด์ของมอร์ตาร์โดยใช้การวิเคราะห์ภาพ

Abstract

The carbonation process in cement-based materials has received increasing attention due to its potential for capturing carbon dioxide and supporting the development of carbon-negative concrete in the future. Traditional evaluation methods, which typically rely on spraying phenolphthalein solution and measuring the depth of the color change, often encounter inaccuracies—particularly when CO₂ absorption occurs unevenly across the specimen surface. This study aims to apply an image-based analysis technique to evaluate the carbon dioxide uptake of mortar under accelerated carbonation conditions, thereby enhancing the accuracy of quantitative assessment. Mortar specimens were prepared with water-to-cement ratios (w/c) of 0.35, 0.50, and 0.65, and the effects of replacing 20% by weight of cement with metakaolin and calcined clay were also examined. The specimens were cured in a sealed chamber containing 40% CO₂ by volume for 7, 14, and 28 days. After curing, carbonation degrees were quantified using the image-based analysis technique. The results indicated that mortars with higher water-to-cement ratios exhibited substantially greater CO₂ uptake. Additionally, cement replacement with calcined clay provided carbonation performance comparable to the control mortar, whereas metakaolin resulted in reduced CO₂ uptake. A comparison between the depth-measurement method and image-based analysis revealed consistent trends, with the image-based approach capable of evaluating both uniform and non-uniform carbonation patterns. Overall, the findings confirm that image-based analysis is an effective and reliable technique for assessing the CO₂ uptake of mortar.