Low-carbon and sustainability considerations of soil waste stabilisation

The aim of this study is to propose a sustainable framework for soil stabilisation by integrating strength, durability, and stabiliser type (i.e. cement and soil stabiliser). A new index, I_cse (i.e. (UCS₁₀₀/UCS₂₈)/(CO₂×D)) was developed to reflect the relationship between unconfined compressive strength (UCS), carbon dioxide emission in the production stage, and dosage to represent the efficiency of strength development in soil stabilisation. Experiments were conducted on two soil wastes (i.e. Wenzhou and Guangzhou soils) and Kaolin. The results showed that UCS alone was insufficient for sustainable consideration, as stabilised soils may exhibit good early strength but poor durability under wet–dry or freeze–thaw cycles, highlighting the need to use I_cse to indicate long-term performance. For cement-treated soils, I_cse ranged from 6 to 11 at 10% to about 5 at 20% for all three soils. In contrast, stabiliser-treated soils showed several times higher I_cse values compared with cement-treated soils. A 1-year field experiment was also conducted to evaluate the long-term performance under natural exposure, demonstrating the stabiliser’s continued strength development. However, I_cse in this study was based on a simplified carbon assessment model that considered only production-stage carbon dioxide emissions and future work can be extended to analyse the full life cycle and cost assessment.