摘要
MgO solidification carbonation technique is a low-carbon and efficient green modification method, but it is not clear on how to analyze the carbonation degree and carbon absorption capacity of carbonated soil. The quantitative analysis system of carbon absorption capacity of MgO solidification carbonation soil was established by quantitatively measuring the CO2 absorption and unidirectional carbonation depth of MgO solidification carbonation soil under the conditions of different MgO contents and carbonation time. The macro and micro mechanism of carbonation process from the perspective of carbon absorption was explored, and the reasons for slowing down of carbonation reaction in the carbonation process were analyzed. The test results show that increasing the MgO content promoted the specimen to absorb more CO2, and the specimen was fully penetrated in a shorter time. The degree of carbonation reaction can be determined by the decreasing trend of water content. The lower the MgO content was, the longer the carbonation time was required for the fully penetrated specimen. The fitting results showed it only took 2 h to fully penetrate when the MgO content was 9.48 %, but it was difficult to fully penetrate when the MgO content was less than 3 %. With the progress of carbonation reaction, increasing MgO content can improve the carbonation rate decreased, and the carbonation proportion and carbonation density simultaneously, up to 126 kg/(h∙m3), 0.79, 197 kg/m3. It was estimated that the waste soil in the shield section of Jiangyin Jingjiang Yangtze River tunnel can absorb up to 760,000 tons of CO2, which was equivalent to the carbon emission from the production of 950,000 tons of quicklime.In the deepening period of carbonation reaction, MgO/Mg(OH)2 was wrapped and cannot participate in the reaction, resulting in the soil cannot be completely carbonated.
•The carbonation acceleration device is used to realize the quantitative measurement of CO2 absorption considering water evaporation loss.•The macro and micro mechanism and three-phase model diagram of carbonation reaction are improved and proposed.•A triple-index evaluation system was established to quantify the CO2 absorption ability of MgO modified soil.•Mechanisms behind slowed carbonation were systematically explained.