Key Parameters for the Strength Control of Lime Stabilized Soils

The addition of lime is an attractive technique when the project requires improvement of the local soil. The treatment of soils with lime finds an application, for instance, in the construction of pavement base layers, in slope protection of earth dams, and as a support layer for shallow foundations. However, there are no dosage methodologies based on rational criteria as exist in the case of the concrete, where the water/cement ratio plays a fundamental role in the assessment of the target strength, and in the case of soil–cement technology, where the voids/cement ratio is shown to be a good parameter for the estimation of unconfined compression strength. This study, therefore, aims to quantify the influence of the amount of lime, the porosity, and the moisture content on the strength of a lime-treated sandy lean clay soil, as well as to evaluate the use of a water/lime ratio and a voids/lime ratio to assess its unconfined compression strength. A number of unconfined compression tests and measurements of matric suction were carried out. The results show that the unconfined compression strength increased linearly with the increase in the lime content as well as with the reduction in porosity of the compacted mixture. The change in moisture content has not presented an obvious effect on the unconfined compression strength of mixtures compacted at the same dry density. It was shown that, for the soil–lime mixture in an unsaturated state (which is usual for compacted fills), the water/lime ratio is not a good parameter for the assessment of unconfined compression strength. In contrast, the voids/lime ratio, defined as the ratio between the porosity of the compacted mixture and the volumetric lime content, is demonstrated to be the most appropriate parameter to assess the unconfined compression strength of the soi-lime mixture studied.