Abstract: The lignin， an industrial by-product， is utilized to improve the silt. A series of laboratory tests on moisture content， particle size distribution， compaction， unconfined compression strength and electrical resistivity are carried out to study the mechanical and physical properties of natural silt and lignin-improved silt. The pH value and electrical characteristics of improved soil are also investigated. Scanning electron microscopy (SEM) is used to analyze the variations of soils microstructure， and the stabilization mechanism of lignin-treated silt is preliminarily discussed. The results indicate that lignin can effectively improve the particle size distribution and reduce the plastic index of soil. As to improved silt， maximum dry density increases， the optimum moisture content decreases， while the change of dry density with moisture content is enhanced. The lignin-treated silt has greater strength performance than the natural silt in terms of unconfined compression strength and all the improved soils have a pH value lower than 10. Curing time and moisture content have a significant impact on unconfined compression strength， but little effect on pH value. The pores of soils are filled and particles are connected with cementing material， then a more stable soil structure was formed. It is shown that adding lignin can successfully improve the basic engineering properties of silt.

Key words: lignin, silt, physical properties, strength characteristic, electrical resistivity