Reexamination of Lime Stabilization Mechanisms of Expansive Clay

For the purpose of understanding the mechanism that results from treating expansive soil with lime, a series of tests were conducted on selected Nanyang expansive clay. X-ray diffraction tests indicated that the major clay minerals of Nanyang expansive clay are a mixture of illite and smectite with some kaolinite and chlorite. The scanning electron microscope images obtained at different curing times were used to interpret the change in the microstructure and the formation of new products from the lime treated samples. The atomic absorption method was adopted to test the concentration of Ca2+ and K+ in the pore water and exchange complex of lime treated Nanyang expansive clay. The results indicate that (1) cation exchange, ions crowding, formation of Ca(OH)2·nH2O, agglomeration, and breaking of clay particles in a high pH environment are the dominant reactions in the early stage of treating expansive clay with lime; and (2) the pozzolanic reaction and carbonation occurred at a late stage after lime treatment (90 days in this study).