Assessment Method of Carbonation Degree and Activity of a Wide Range of Calcium/magnesium Containing Solids

This work provides a systematic analysis and comparison of the assessment methods for determining the carbonation degree of materials containing calcium or magnesium. The analysis is conducted from three key perspectives, namely the consumption of carbonation reactive components, the production of carbonation product and the dry mass change resulted from carbonation reaction. The carbonation degree of steel slag, tricalcium silicate and carbide slag were assessed at liquid-to-solid ratios of 0 and 0.15 using quantitative X-ray diffraction, thermogravimetry and weighing at temperature of 25 °C, relative humidity of 60% and carbon dioxide concentration of 40%. The utilization of scanning electron microscope was employed to reveal the significant impact of liquid water on the carbonation degree. The results indicate that the carbonation degrees obtained by X-ray diffraction and thermogravimetry are quite similar, whereas the values obtained through weighing method drift away a little, particularly when liquid water is present. Nevertheless, all the methods investigated in this study exhibit great consistency and reliability, including the dry mass change method given its acceptable deviation from others and its convenience in testing. Furthermore, a novel method on assessing the carbonation activity is proposed based on the 24-h carbonation degree at the liquid-to-solid ratio of 0.15, which enables to efficiently distinguish the carbonation potential of different materials. In the end, carbonation activity inventory is established in which a wide range of calcium/magnesium contained materials are categorized into five groups, suggesting its suitability for evaluating the carbonation activity of various solid wastes and cement-based materials.