Carbon sequestration potential and mechanisms of shotcrete for tunnel support in underground metal mine under cement hydration

Growing concerns about greenhouse gas emissions from underground mining have heightened scrutiny, making it crucial to implement carbon reduction strategies at every stage, with shotcrete used in tunnel support offering a promising opportunity to reduce emissions.This paper investigates the carbon absorption capacity, mechanical strength, and underlying mechanisms of shotcrete when exposed to varying carbon dioxide (CO2) concentrations during the mine support process. The findings reveal that higher CO2 concentrations during the initial stages of carbonation curing enhance early strength but may impede strength development over time. Specifically, shotcrete samples exposed to 2% CO2 for 14 days exhibited a carbonation rate approximately four times higher than those exposed to 0.03% CO2. A significant carbonation layer formed in the shotcrete, sequestering CO2 as solid carbonates. In practical terms, shotcrete in an underground return air tunnel absorbed 1.1 kg of CO2 per square meter over 14 days, equivalent to treating 33 m3 of contaminated air. Thus, using shotcrete for CO2 curing in return air tunnels can significantly reduce carbon emissions, contributing to greener and more sustainable mining practices..