Experimental study on the engineering characteristics of modified silt in the Yellow River alluvial plain

The silt in the alluvial plain of the Yellow River is characterized by uniform particle size, high porosity, and large material compressibility, which poses a challenge for filling roadbeds in this area. The study investigated the impact of lignin and construction waste fine aggregate on the physical and mechanical properties of the modified silt. The construction waste modified silt with a fine aggregate content of 30% construction waste has good compressive strength, shear strength, and degree of consolidation. The lignin modified silt with 0.5% lignin concentration has higher compressive strength, cohesiveness, internal friction angle, and compression modulus. The fuzzy comprehensive evaluation identified the optimum proportioning of 1% lignin and 40% construction waste fine aggregate for the composite modified silt and the engineering characteristics and modification mechanism of the optimum modified silt were analyzed. The California bearing ratio (CBR) test results indicated that the value of optimum composite modified silt silt increases by 118.48% compared to the plain silt, and it meets the requirements for subgrade fill as specified in the guidelines. The scanning electron microscope (SEM) test results showed that the addition of lignin and fine aggregate improved the grain composition and enhanced the silt compactness. The study demonstrates that incorporating lignin and fine aggregate in silt material can enhance its engineering properties, thereby meeting the minimal standards of filling highway subgrades. These findings can serve as a valuable reference for enhancing the quality of silt in the region.