Preparation and carbon sequestration properties of supercritical CO2 foamed concrete

Abstract

Realizing green and low-carbon development will be a new requirement facing the coal industry. In order to address this problem, this paper proposed a method of preparing foam concrete using a supercritical CO2 phase change foaming technology, and a Portland cement-based supercritical CO2 foamed concrete with both high pore structure and carbon sequestration capacity was prepared. The effects of supercritical CO2 on the dry density, pore structure and carbon sequestration capacity of the material and its mechanism were investigated. The experimental results revealed that the supercritical CO2 phase change foamed concrete preparation process is a temperature-pressure dynamic coordination process considering Portland cement properties and its reaction properties with CO2 mineralization. The mechanism of Portland cement-based foamed concrete prepared by the supercritical CO2 phase change foaming technology may be divided into four stages: CO2-cement slurry coexistence, CO2-cement slurry co-solution, supercritical CO2-cement slurry co-solution, and unpressurized foaming. Increasing the experimental pressure can increase the CO2 concentration in the supercritical CO2-concrete system and reduce the dry density of supercritical CO2-foamed concrete, which varies from 787.14 to 993.52 kg/m3 with a range of 8.28% to 19.20%. The development of porosity of supercritical CO2 foamed concrete was affected by the diffusion-dissolution behavior of CO2 in the supercritical CO2-concrete system, and its porosity was 47.87%−89.79%. Increasing the experimental pressure and optimizing the holding time are the development direction for preparing supercritical CO2 foamed concrete with high porosity. The supercritical CO2 foamed concrete has uniform, regular and independent circular pores with approximately the same pore diameter of 0.2 mm. Increasing the experimental pressure can promote the degree of CO2 mineralization reaction and effectively optimize the structure and distribution density of the pores. Each tonne of supercritical CO2 foamed concrete has a carbon sequestration capacity of 6.32%−10.36% in the skeleton and 0.98−2.27 kg in the pore, which has obvious carbon sequestration potential, but the preparation process and parameters still need to be further improved. The results show that the supercritical CO2 foamed concrete is expected to be developed into a functional material with near-zero-carbon for mining, which is of great significance for realizing the carbon reduction at the source of coal power integration base.

Keywords

• green and low-carbon
• supercritical carbon dioxide
• mineralization and storage
• foam concrete
• mine materials