Effect of carbonation and foam content on CO2 foamed concrete behavior

Coal and electricity integration plays an important role in ensuring national energy security, but it still faces the challenge of carbon emission reduction. The development of in-situ CO2 sequestration and utilization technology for pithead power plants is an effective way to achieve low-carbon and efficient utilization of coal power. The preparation of foam concrete for mining using CO2 is a type of carbon capture, utilization, and storage technology featuring in-situ CO2 sequestration and utilization in pithead power plants and mine filling and sequestration. The purpose of this study is to evaluate the basic performance and carbon sequestration potential of Portland cement-based CO2 foam concrete (PC-CFC) as a mining material. In this study, PC-CFC was prepared through physical foaming and the carbonation pretreatment cement process. The influence of carbonation pretreatment time and CO2 foam content on density, strength, and carbon sequestration of PC-CFC was investigated. The experimental results showed that carbonation pretreatment could enhance the stability of CO2 foam in Portland cement and improve the CO2 foaming performance. With the extension of carbonation pretreatment time, the extend of dry density reduction decreases from 16.6% to 0.8%. A 60 min–90 min of carbonation pretreatment can achieve the best treatment performance. Carbonation pretreatment and CO2 foam can promote the degree of cement hydration, optimize the PC-CFC pore structure, and improve the compressive strength of PC-CFC. However, the PC-CFC material strength owing to the extended carbonation treatment time, which leads to well-developed vesicle distribution, has an overall decreasing trend. In addition, the 7 day (d) compressive strength of PC-CFC can reach more than 60% of the 28 d compressive strength, which has evident early strength characteristics. Extending the carbonation pretreatment time and CO2 foam content increased the PC-CFC carbon sequestration that ranged from 61.0 kg/ton to 85.7 kg/ton. The dry density of the PC-CFC material was significantly and positively correlated to the 28 d compressive strength and negatively correlated to the amount of carbon sequestration. In the case in which the best carbon sequestration effects is achieved, a single filling of the working face end can store ∼3929.31 kg of CO2; in the most economical condition, it can store ∼3642.79 kg of CO2. The conducted research provides new ideas for the low-carbon and green development of coal and electricity integration.