Novel use of calcium sulfoaluminate (CSA) cement for treating problematic soils.

• Sustainable way of ground treatment was investigated using CSA cement. • CSA cement showed significant and rapid strength improvement for expansive soils. • Key phases of stabilization mechanism of CSA cement for expansive soils are unveiled. • Stabilization follows cationic exchange and flocculation and agglomeration. • Subsequently, cementitious hydration form space filling ettringite needles. Expansive soils are a common problem to overlying geotechnical structures risking for distress and damage caused by moisture induced ground movements. Calcium-based stabilization is readily adopted to improve and enhance the problematic expansive subgrade increasing strength and the volume change behaviour. For ground improvement, the use of lime and Ordinary Portland Cement (OPC) to treat expansive soil has been in common practice; however, Calcium Sulfoaluminate (CSA) cement can be an effective alternative due to the reduced environmental impact. To date, limited literature surrounds the understanding of CSA cement in expansive soil, but largely focussed its applications on concrete infrastructure. This paper investigates the stabilization mechanism of CSA treated expansive soils by identifying the major hydration products and microstructural characteristics with respect to CSA cement dosage and curing rate. The study reveals CSA cement stabilization directly affects mechanical properties and microstructural characteristics due to three key phases of cationic exchange, flocculation and agglomeration between the clay sheets and cementitious hydration. The addition of CSA cement in the ground stabilization serves to shift towards a sustainable approach in reducing the carbon impact of traditional stabilization techniques. [ABSTRACT FROM AUTHOR]