Stabilization of organic soils using lime dust

The engineering properties of four organic soil, a peaty organic soil, a peat, and lime dust were determined in the lab. The properties determined included grain size distribution, Atterberg limits, water content, organic content, specific gravity, acidity, bulk density, compaction characteristics, permeability, shear strength parameters, volumetric shrinkage, and consolidation behavior. Lime dust-soil mixtures containing 10%, 20%, 30%, 40%, and 50%, lime dust by weight were tested for compaction characteristics and permeability. Optimum mixes of soil and lime dust were tested for acidity, Atterberg limits, shear strength parameters, and consolidation behavior. The results indicate that the bulk of the particles of the organic soils are in the sand-silt size range and that lime dust can be classified as a silty sand (SM) according to the Unified Soil Classification System. The results also show that natural water content and volumetric shrinkage increase whereas specific gravity, bulk density, and maximum dry density decrease with increasing amounts of organic content. The optimum moisture content was found to be zero for soils with organic content exceeding 30%. For lime dust-soil mixtures, the maximum dry density increases with increasing amounts of lime dust. In this case, the optimum mix was chosen as the one whose maximum dry density was above the density of water (62.4 pcf; 1 Mg/m(3)). Soils with organic contents below 50% meet this criterion with the addition of 30% lime dust. For soils with more than 50% organic content, 60% lime dust is needed to achieve the desired density. Lime dust has little effect on the permeability of organic soils. However, shear strength at 1000 Ibs. normal force increases up to 66% with the addition of optimum amounts of lime dust. For the optimum mixes, the plasticity and compression indices generally decrease, whereas the pH values increase. The results of the study show that lime dust can be used to improve all desirable properties of organic soils, rendering them suitable for specialized construction.