Effect of Lime, Cement, and Lime-Cement Stabilisation on Low to Medium Plasticity Clayey Soil

The volumetric changes of clayey subgrade soils can be very significant due to their sensitivity to moisture variation and for some, strength is also affected. The latter may cause instability of the pavement and early deterioration or failure. Chemical stabilisation of such soils with lime or cement has proven to be more economically and environmentally sustainable than other methods. They are cheaper than removal and replacement in addition to avoiding dumping useful natural resources in landfills. Combined two-stage lime and cement (lime-cement) stabilisation of clayey soils, with all plasticity levels, have been used successfully for many years, however, there are no existing guidelines or specifications for the optimum design mixtures and construction process. To address this, a comprehensive laboratory testing program has been developed to establish the optimum lime-cement combinations for different soils. Reported herein are the experimental program and testing results for a medium plasticity clayey soil stabilised with lime, cement and lime-cement. For the soil tested herein, the results have shown that lime stabilisation using minimum lime demand helps to increase compressive strength, bearing capacity and hydraulic conductivity of the soil, while decreasing its plasticity. Additionally, it has been found that low cement contents produce enough strength for the subgrade soil. Further, modifying soil's workability with lime before stabilising it with cement has proved very effective in producing favourable improvements in physical and mechanical properties of the testing soil.