Abstract: To promote the low carbonation of construction materials, this study proposed a design approach for biochar-enhanced CO₂ foamed concrete, systematically investigating its mechanical, thermal, and carbon-reduction performances, as well as elucidating the influence and role of biochar on carbonation curing. Results demonstrate that the porous structure and high specific surface area of biochar significantly improve CO₂ transfer and interfacial reactivity, thereby accelerating carbonation reactions and enhancing both carbonation depth and CO₂ sequestration efficiency. Furthermore, 5% (mass fraction) biochar incorporation increases the compressive strength of foamed concrete by up to 15%, while simultaneously reducing thermal conductivity, thereby improving thermal insulation performance. In addition, through a "negative-carbon material+carbon reduction substitution+active carbon sequestration" tri-fold carbon mitigation strategy, at a 10% (mass fraction) biochar replacement level, the unit carbon footprint of the foamed concrete decreases by approximately 60.6%. This study elucidates the mechanisms by which biochar enhances the performance and carbon sequestration of CO₂ foamed concrete, providing both theoretical and experimental support for the development of green, low-carbon construction materials.

Key words: foamed concrete, biochar, carbonation curing, compressive strength, carbon sequestration