Sorry, you do not have permission to ask a question, You must log in to ask a question. Join now! Do you need to remove the ads? Lime-Soil stabilization is the process of adding lime to the soil to improve its properties like density, bearing capacity etc. Various factors affecting lime-soil stabilization are soil type, lime type, lime content used, compaction, curing period and additives which are briefly discussed below.
The principle involved in lime-soil stabilization is the exchange of ions between lime and soil when added. When clayey soil is treated with lime, Cation exchange takes place between them which increases plastic limit and reduces plasticity index which finally results in increase in stability of soil.
If clay contains gravel in it, then lime acts as binding material for clayey gravel. Lime-Soil stabilized mix are useful to construct sub-base and base course for pavement. Lime treated soil is more suitable for warm regions where temperature is very high and for colder regions it is not suitable.
Join Join TheConstructor to ask questions, answer questions, write articles, and connect with other people. Have an account? Log in Now. The application of lime can significantly improve the engineering properties of soil. There are essentially two forms of improvement: soil modification and soil stabilization.
The use of lime can modify almost all fine-grained soils to some extent, but the most dramatic improvement occurs in clay soils of moderate to high plasticity.
Modification occurs primarily due to the exchange of calcium cations supplied by the hydrated lime for the normally present cation adsorbed on the surface of the clay mineral. Modification is also caused by the hydrated lime reacting with the clay mineral surface in a high-pH environment: the clay surface mineralogy is altered as it reacts with the calcium ions to form cementitious products.
The results are plasticity and swelling reduction, reduced moisture-holding capacity and improved stability. Soil stabilization occurs when the proper amount of lime is added to a reactive soil. Stabilization differs from modification in that a significant increase in strength is developed over the longer term through an on-going pozzolanic reaction.
Lime stabilization uses pozzolans, which are naturally present in clay soils, to generate cementitious bonds that permanently strengthen a soil. Pozzolans such as silica and alumina react with calcium, supplied by the lime, and water to form calcium-silicate-hydrates C-S-H and calcium-aluminate-hydrates C-A-H. The term lime can be used somewhat inconsistently. For soil stabilization purposes, the term lime must mean either quicklime or hydrated lime. Farmers sometimes refer to agricultural lime, finely ground calcium carbonate CaCO 3 , as lime.
While this form of calcium helps farmers improve their soil by amending their fields, using it would not gain any strength in the soil under the feet of a construction worker. It is worth noting that quicklime can come in two types, high calcium and dolomitic. High calcium is almost completely calcium oxide CaO , whereas dolomitic quicklime contains a portion of magnesium oxide along with calcium oxide.
While some industrial applications such as steel need the magnesium component for certain processes, for construction purposes high calcium and dolomitic are virtually indistinguishable. Hydrated lime is quicklime that has been further processed.
It has been carefully hydrated with the proper amount of water and agitation to produce a very fine, high-purity product. Hydrated lime can still supply the calcium that is essential to stabilize certain soils by forming cementitious bonds.
However, since the material has already been hydrated, it does minimize much of its drying capacity that is desired on wet job sites. Also, hydrated lime is only available in certain areas and there are additional costs for the added processing.
Lime kiln dust LKD , is derived during the quicklime manufacturing process as a co-product. It is made up of the finely sized particles that are captured in the baghouse at a lime plant. These particles are high calcium or dolomitic lime plus pozzolans from the fuel used to fire the lime kiln.
Because it contains both lime and pozzolans, LKD is a hybrid between lime and cement. As previously mentioned, lime works very well with fine-grained soils.
Cement, on the other hand, works very well with coarser gained soil. LKD bridges the gap between the two. Soil cement stabilization is a construction technique used to increase the strength of subgrade soil by mixing it with cement and water. The water hydrates the cement, generating reactions that create a matrix between the soil particles and gives the soil strength.
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