Cement choice makes or breaks construction on toxic soils, study shows

Abstract Sulfide-rich soils (also called potential acid sulfate soil), with their sulfur content, and potential to generate acidity, pose challenges for construction due to low bearing capacity, shear strength, and their acidification potential. This study compares the effectiveness of Portland cement and Multicem binders in stabilizing these soils by analyzing unconfined compressive strength (UCS), porosity, pH changes, and strain behavior. Four soil samples with varying state of oxidation, pH, sulfur content, and water content were treated with binders at different dosages and analyzed after 28 days of curing. The results demonstrate that binder type and dosage, initial pH, and soil composition together significantly influence stabilization performance. Portland cement achieved higher UCS values across all samples, particularly in soils with low pH, due to its high alkalinity and facilitation of hydration reactions. In contrast, Multicem achieved acceptable UCS in soils with moderate initial pH, as its slower hydration limited its effectiveness in highly acidic conditions. Porosity reduction in stabilized samples correlated with increased binder content. Strain behavior exhibited an inverse relationship with UCS. Higher UCS samples showed reduced strain, indicating increased stiffness. However, in oxidized and highly acidic sulfate soils, such as Sunderbyn, UCS gains were limited, suggesting that extreme pH conditions inhibit binder effectiveness. The study offers practical guidance for optimizing binder selection and application strategies, especially for the treatment of acid sulfate-rich soils in geotechnical engineering. Future research should prioritize the assessment of durability, stability and performance under varied environmental stresses to ensure sustainable solutions.