Solidification characteristics and carbon reduction efficacy of a novel magnesium oxide-based steel pipe carbonation composite pile

To address the significant carbon footprint challenge of existing ground treatment methods, a novel magnesium oxide-based steel pipe carbonation composite pile (MSCP) technology was proposed. Field tests, microstructural characterization, and carbon footprint assessments were conducted to evaluate its solidification characteristics and carbon reduction efficacy. Results indicate a significant positive correlation between the maximum temperature increment (Δ T max ) of the MSCP outer pile and its 14-d unconfined compressive strength ( q u ), providing a real-time strength control method based on critical and safe Δ T max . Higher gas injection flow rates are found to significantly enhance carbonation uniformity and sufficiency. Microscopic observations reveal that the hydrated magnesium carbonates (HMCs) reshape the soil microstructure through densification, filling, interlocking, and cementation. The carbon emissions of MSCP single-pile are reduced by approximately 30% compared to traditional solutions, primarily stemming from the use of low-carbon binders and the utilization of industrial CO 2 tail gas. MSCP technology not only offers a new ground treatment method for soft ground with controllable performance, but also opens up a new pathway for carbon sequestration and emission reduction in geotechnical engineering.