Review of chemical stabilizing agents for improving the physical and mechanical properties of loess

Due to the special soil-forming environment and process, grain-size distribution, and mineral composition, loess has some poor engineering properties, such as high compressibility, strong water sensitivity, and severe collapsibility. These poor properties lead to frequent occurrence of geological disasters and engineering problems in loess area, so loess is often strengthened in engineering projects. Compared with the traditional methods, the use of stabilizing agents has the advantages of saving time, reducing cost, and increasing efficiency. Therefore, more and more attention has been paid to the research on soil stabilizing agents. In this review, the non-traditional stabilizing agents which can effectively improve the physical and mechanical properties of loess are summarized, including nanomaterials, industrial waste residues, water-hardening inorganic materials, polymer, ion stabilizing agents, and so on. The composition, mechanism, effect, and application of each stabilizing agent are introduced. The mechanisms of strengthening mainly include filling, cementation, ion exchange, and wrapping. One or several of these mechanisms work together when loess is strengthened with any stabilizing agent. Based on this review, it is recognized that it is still meaningful to find eco-friendly and cost-effective loess stabilizing agents, and the focuses are now still on interpretation of the mechanism of each stabilizing agent, as well as determination of the physical and mechanical properties of strengthened loess. Attention should be paid to the degradation in the mechanical properties of strengthened loess and the technical innovation in application, as well as to solving the problems related to practical application of these stabilizing agents.