Study on Strengthening and Waterproofing Mechanism of Calcium Lignosulfonate in Silty Soil Sites

Silty sites are affected by natural and human factors, have a low soil strength and strong water sensitivity, and are prone to cracks, soil peeling, and other failures that urgently need to be repaired. Calcium lignosulfonate (CLS) from paper plant waste fluids is a natural bio-based polymer. In this paper, against the background of the reinforcement and protection project of the Qingtai Site in Xingyang, Henan Province, silty soil was modified by adding CLS, and the material ratio with the best restoration effect was determined by carrying out a series of mechanical and waterproof tests. The mechanism of action of the modified materials was analyzed through microscopic tests such as SEM and XRD. The test results showed that a 1.0% mass fraction of CLS in the silty soil was the optimal ratio of the modified material. The mechanical properties of the modified soil first increase and then decrease with the increase of CLS content, and the waterproof properties increase with the increase of CLS content. The lignosulfonate polymer generated by the displacement reaction between CLS and the soil particles was cemented with the soil particles, meaning that the mechanical and waterproof properties of the modified soil were improved. And the content of the main elements and the mineral composition in the modified soil did not change. The research results provide a reference for the restoration and protection of silty sites.