Efficacy of Sucrose and Skimmed Milk in Enhancing Sandy Soil Strength Using the SCU-CP Method

The Soybean Crude Urease Calcite Precipitation (SCU-CP) method is a bio-mediated soil improvement approach that promotes calcium carbonate precipitation through enzymatic urea hydrolysis. Although this method has shown potential for sustainable soil stabilization, its efficiency is often limited by the non-uniform distribution of calcite, which affects interparticle bonding and the overall improvement in soil strength. This study aims to enhance the performance of the SCU-CP method through the use of natural organic additives, specifically sucrose and skim milk, to improve the homogeneity of calcite precipitation and increase the strength of the treated sandy soil. Experimental investigations were conducted using soybean extract concentrations of 20, 60, and 100 g/L, combined with sucrose and skim milk additions of 2.0, 4.0, and 6.0 g/L. Experimental tests, including precipitation, hydrolysis, viscosity, water holding capacity, and unconfined compressive strength (UCS), were conducted to examine the influence of these additives on the grouting characteristics and soil performance. The results showed that the addition of sucrose and skim milk increased the solution viscosity and water retention, which facilitated a more uniform distribution of calcite crystals within the soil matrix. This improvement in calcite uniformity strengthened the interparticle bonding and resulted in a substantial increase in the UCS. The optimum performance was obtained using 6.0 g/L skim milk, resulting in an approximately 90% increase (21.3 kPa) in UCS compared with untreated sand, whereas 6.0 g/L sucrose produced a 49% improvement (18.4 kPa). Overall, the use of natural organic additives improved the microstructural integrity and grouting behavior of the SCU-CP method. These findings provide a reference for improving enzyme-induced soil stabilization techniques and indicate the need for further research on organic content, calcium chloride optimization, and multicycle treatment to support potential field-scale applications.