Scaled model test into the spatial variability and carbon storage potential of carbon sequestration foamed concrete as a subgrade filler

Abstract

To minimize the differential settlement between the existing and widened embankments, while promoting the CO₂ emissions reduction and the abandoned soil reuse during the construction process, a novel carbon sequestration foamed concrete (CFC), which replaced ordinary Portland cement with magnesium oxide (MgO) and replaced air foam with carbon dioxide (CO₂) foam, was proposed. A scaled model test of CFC was designed to simulate the actual working conditions of subgrade filling engineering, with the application performance evaluated by the temperature monitoring and thermal cone penetration test (T-CPT). Samples were subsequently drilled from the CFC model for analysis. A series of tests, including unconfined compressive strength, phase identification, and microstructure were conducted to assess its spatial variability and low carbon potential. The results revealed that the internal temperature of the CFC scaled model reached nearly 50 ℃ within 20 h. The strength, penetration resistance, and CO₂ sequestration capacity of the CFC gradually decreased with increasing depth while the density exhibited a gradual increase. Significant formation of carbonates was observed in the scaled model samples, serving as the primary source of strength. The research findings can contribute to the large-scale field application and widespread adoption of CFC technology.