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Quicklime reduces the water content in land by means of three actions: the addition of dry material, the consumption of water necessary to hydrate the lime and the evaporation of water due to the heat generated by the hydration reaction. On a very sunny day with a wind airing the land over a number of hours, humidity can be reduced by up to 6 points. In addition, it can be used to defrost a blot of land. The end result is that land that was unusable due to its level of water saturation is made manageable, allowing work to continue on site (machinery access, stacking of material on site, etc.).
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The lime used for soil stabilisation produces complex ionic changes, neutralisation and flocculation, which result in the clay particles taking on a granular structure, reducing the index of plasticity and eliminating swelling. The land goes from an initial laminar structure (the plastic state of sticky and easily deformable soil) to the formation of agglomerates (a solid state in which the material is rigid and friable). At the same time as these effects are taking place, the load-carrying capacity of the land begins to increase.
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The incorporation of a strong chemical base like lime during the stabilisation process gives rise to an increase in the pH of the land until it reaches a value of 12.4: at this point, all the silicates and aluminates present in the land increase their solubility, reacting with the calcium by means of ionic exchange to form hydrated calcium silicates and hydrated calcium aluminates (pozzolanic reactions), giving rise to cementitious material in between the particles that form the land. The end result is an increase in the load-carrying capacity of the land and in mechanical resistance, as well as an increase in land non-permeability and frost resistance: major increases in CBR, an increase in resistance to cutting, traction and unconfined compression, and improved stability, reducing expansion and contraction. This reaction usually lasts for a period of time from several months to 2 years. |
