<p>Sequestering CO₂ via soil improvement offers a promising pathway to carbon reduction. This study explored the use of amorphous calcium carbonate (ACC) cement for both decarbonization and ground improvement. Derived from waste carbide sludge and CO₂, ACC-cement was used as a binder for soil treatment through microbially induced carbonate precipitation (MICP) and crystal transformation processes. The mechanical properties and CO₂ sequestration capacity of ACC-treated materials mainly depend on the urease activity, initial ACC-cement content, and treatment cycles. Further experiments were carried out to optimize both the strength gain and CO₂ storage capacity. Results showed that the ACC-cement can be transformed into a strong binder to soil particles through calcite crystal growth. The gain in compressive strength of the treated soil is mainly controlled by the calcite content, and the urease activity of ACC-cement affects the ACC transformation and calcite formation. An optimal ACC-cement content exists to achieve the highest compressive strength of a given soil. These findings highlight the ACC-cement’s dual role in soil improvement and carbon sequestration, shedding light on optimizing treatment parameters across diverse soils.</p>