Effects of Lime on Permeability and Compressibility of Two Tropical Residual Soils

An investigation of the effect of hydrated lime on the permeability and compressibility of two Brazilian soils: a brown saprolitic soil, Soil 1, and a red lateritic soil, Soil 2, is presented. Details of the test methods and materials are given. The results obtained show that the coefficient of permeability of Soil 1 increased about fivefold when 2% lime was added and then decreased on further addition of lime. This is attributed to the creation of chemical bonds and aggregation. As for Soil 2, the coefficient of permeability decreased as lime was added. This is also attributed to the same mechanism except that the bonds are weaker than those developed in Soil 1. The resistance of the soil to compression improved substantially, on the addition of 4% lime. The soils exhibit less improvement on further addition of lime. Lime was also found to be effective in decreasing the potential for collapse of the two soils when compacted to densities lower than their maximum dry densities.