REVIEW ON STRENGTHENING LOESS WITH CURING AGENTS

Special soil genesis, grain-size distribution and mineral composition render loess soils poor engineering properties, such as high compressibility and strong collapsibility. This bad characteristic leads to frequent disasters in loess area, and loess needs to be strengthened in order to meet the needs of construction. Compared with traditional strengthening methods, the use of curing agent to reinforce loess soils has advantages of time-saving, labor-saving, low cost and good effect. For this reason, this method has received extensive attention. In this paper, a variety of curing agents which were found to be capable of improving the engineering properties of loess soils effectively are summarized, including nanomaterials, inorganic hardeners, organic polymer materials, biological enzymes and mineralized bacteria. The composition, reinforcement mechanism and reinforcement effect of each curing agent are detailed. Because of small size and large specific surface area, nanomaterials would wrap soil particles to form aggregates of small sizes, which would fill inter-particle or inter-aggregate pores, thus the soil density and uniformity are increased. Inorganic hardeners play the role of cementing and filling in the soil. Organic polymer materials destroy the weak bound water film on the surface of soil particles by ion exchange, the attraction between particles is then improved and the soil density is increased. In addition, organic polymer materials are cements and fillings in the soil structure. Biological enzymes improve the activity of organic macromolecules in the soil through catalysis, resulting inorganic films of cementing and water-blocking functions. Calcium carbonate, the metabolite of mineralized bacteria, would fill soil pores and connect soil particles. On the basis of an insight understanding of the existing researches, we believe that the study of strengthening loess should be paid more attention to:(1)timeliness of the reinforcement effect of curing agents; (2)the application of curing agents in loess engineering, including the construction technology taking account of the difference in engineering conditions; (3)the interaction between environmental factors and strengthening loess with curing agents.