The carbon uptake and mechanical property of cemented paste backfill carbonation curing for low concentration of CO2

Large volumes of carbon dioxide are released during mining and ore resource development, and cemented paste backfill (CPB) materials are placed in the mined-out stopes where can be discharged from polluted air containing CO2. The construction of green mines and the goal of achieving carbon neutrality have become an inevitable choice for the mining industry to achieve the harmonious development of rational exploitation of resources and environmental protection. Against this background, to minimize the carbon emissions from the mining industry and promote the efficient utilization of CPB, this study investigated the carbon-uptake characteristics and mechanical property of CPB in underground mined-out stopes with 1.5 % concentration CO2. The results show that the carbonation curing (CC) increased the carbonation rate by nearly 4 times compared to natural curing, while the samples exhibited total carbonation within 28 days. This indicates that CO2 uptake could occur within the CPB. The CO2 was absorbed as calcium carbonate minerals, and each ton of CPB can ideally absorb about 78.4 kg CO2 and treat 2600 m3 of dirty air in the mined-out stopes. The increase in early uniaxial compressive strength (UCS) during CC required a higher cement concentrate, and the CC would retard the development of later compressive strength. Microstructure analysis indicated that the CC refined the pore structure and reduced the porosity of the CPB. It also affected the crystal growth and distribution of hydration and carbonation products, further influencing the difference in strength. In summary, CPB technology can potentially be useful during carbon uptake and may assist in mitigating carbon emissions from the mining industry and promoting environment friendly development.