Control of dispersivity of soil using lime and c ement

Dispersion of a sodic soil occurs when it is wetted and the clay particles are forced apart. Thus dispersive soils erode under small seepage velocity leading to problems of stability of earth and earth retaining structures. The extent of dispersion depends on mineralogy and clay chemistry as well as the dissolved salts of the pore fluid. Soil dispersivity is mainly due to the presence of exchangeable sodium present in the structure. The attractive forces are less than the repulsive forces under saturated conditions and this will help the particle to segregate and to move in suspension. The use of lime and cement to bind the soil clay particles and reduce the dispersivity and improve the strength of soil has been studied. The relative performace of them depends on the type of soil and the pore fluid chemistry. It has been shown that 3 percent lime or 3 percent cement can improve the strength of the soil. The rate of improvement of strength is rapid for the first three days and gradual with further curing up to 14 days. The Young's modulus of the soil also increases with the addition of lime and with curing. There is good correspondence between the unconfined compressive strength and Young's modulus for stabilized soils. For the soil under study it was shown that lime is a better additive than cement.