Effect of natural pozzolana on microstructural behavior and hydraulic conductivity of lime-stabilized clayey soil

Considerable changes in mechanical and hydraulic conductivity of soil are produced due to the micro- and macrostructural modification after lime treatment, which influences the water flow and the transport of contaminants in soil. According to the positive results obtained from the stabilization of the clayey soils with the combination of lime and natural pozzolana, it should be determining the influence of both lime and natural pozzolana to the hydraulic conductivity of soil. In order to achieve this goal, the present paper studies the influence of lime, natural pozzolana and their combination on the microstructure modification and hydraulic conductivity variation of a compacted clayey soil classified as a fat clay (CH) according to the unified soil classification system. Natural pozzolana and lime are added to the studied soil at percentages of 0-20% and 0-6%, respectively. Test results show that the use of natural pozzolana increases the maximum dry density and hydraulic conductivity of treated and untreated clay soil with lime and produces a denser soil structure with more flocculated particles. A negative correlation was observed between dry density and hydraulic conductivity; the addition of lime to the clay soil and clay-natural pozzolana leads to a diminution in dry density that causes a considerable increase in hydraulic conductivity when lime content is lower than 4%. On the other hand, adding lime content higher than that decreases hydraulic conductivity. In addition, it can be noted that the hydraulic conductivity of lime-treated clay and clay-natural pozzolana is related to the variation of both macro- and mesopores.