Abstract:
Growing concerns about greenhouse gas emissions from underground mining have intensified the need for carbon reduction strategies at every stage. Shotcrete used in tunnel support presents a promising opportunity for carbon emission reduction. This study investigates the carbon absorption capacity, mechanical strength, and underlying mechanisms of shotcrete when exposed to varying CO
2 concentrations during the mine support process. Findings reveal that higher CO
2 concentrations during the initial stages of carbonation curing enhance early strength but may impede long-term strength development. Shotcrete samples exposed to 2vol% CO
2 for 14 days exhibited a carbonation degree approximately three times higher than those exposed to 0.03vol% CO
2. A carbonation layer formed in the shotcrete, sequestering CO
2 as solid carbonates. In practical terms, shotcrete in an underground return-air tunnel absorbed 1.1 kg·m
2 of CO
2 over 14 days, equivalent to treating 33 m
3 of contaminated air. Thus, using shotcrete for CO
2 curing in return-air tunnels can significantly reduce carbon emissions, contributing to greener and more sustainable mining practices.