Low-Carbon Material Performance in Stabilization of Saudi Marginal Soils Exposed to CO₂ Curing

The local marginal soils in Saudi Arabia’s arid environment show low shear strength and load-bearing capacity, which pose challenges to geotechnical applications. These deficiencies are primarily attributed to the weak particle bonding of silty sand, leading to persistent risks for infrastructure performance. This research evaluates a low-carbon ground improvement route that repurposes ground granulated blast furnace slag (GGBS) and activates it through CO₂ curing, benchmarked against conventional ambient curing. The unconfined compressive strength and California Bearing Ratio tests were conducted as geotechnical performance indicators of locally sourced SM soil treated with varying dosages of GGBS under normal and CO₂ curing. Furthermore, the surface morphology behavior of untreated soil and GGBS mixed soil was examined by using scanning electron microscopy to further support the mechanical strength. The results indicate that GGBS stabilization combined with CO₂ curing significantly enhances early-age compressive strength compared to normal curing. SEM observations reveal refined pore structure and improved particle bonding in CO₂-cured specimens, which explain the observed strength improvement. This approach represents a technically viable, cost-effective, and environmentally responsible stabilization strategy for marginal soils in infrastructure applications. In addition, the use of industrial by-products and reduced reliance on conventional binders aligns with Saudi Vision 2030 objectives for lower-carbon infrastructure and sustainability.