High water content and the presence of clay in soils makes construction works difficult. But lime provides a swift solution to this type of problem, as well as being economical. Lime has three effects on soil stabilization and can be used on unstable soils to dry, modify and stabilize.
Soil stabilization is the process that natural clay soils are subjected to so as to improve their qualities: that is to increase resilience, lower plasticity, aid construction works and increase their stability by lowering the number of problems on structures and surfaces.
The stabilization of clay with lime is not a new invention because this construction technique was used on the pyramids that were built in Tíbet, and it was also frequently used in China and India, although it was not until 1950 that lime treated clay became common, when it began to be used for road and motorway construction, landing-strips etc.
When the geotechnical properties of the ground are unsuitable, carrying out this type of construction works is practically impossible, and so a treatment of the soil in question is almost obligatory.
If this is the case, lime helps to chemically modify unstable soils into usable materials. As mentioned above the use of lime as a binder in construction is a very old practice, but recent improvements related to the purity of the materials employed and the machinery used to apply it, has made it much more common for stabilizing soils.
Lime for the stabilization of soils has many advantages, both economic as well as environmental. For example, the fact that stabilizing soils for construction works with lime, allows the materials present in the zone of the works to be taken advantage of, avoiding the management costs related to this material, which if it were not stabilized with lime would have to be substituted by a suitable alternative material. Thus, stabilizing soils with lime makes works more sustainable, both environmentally as well as economically, because in just a few minutes lime modifies a plastic soil with little load-bearing capacity into a rigid, easily compacted surface with excellent load-bearing capabilities where machinery can operate without any difficulty.
Effects of lime on soil stabilization
There are three effects that the use of lime can have on soil stabilization. Specifically, lime can be used on unstable soils to dry, modify and stabilize.
1- Soil drying: Quicklime (calcium oxide) is very effective in drying any wet soil. After being mixed with the clay soil the quicklime absorbs the water through an exothermic reaction, dramatically lowering the level of humidity in the soil through hydration and evaporation. The level of humidity remaining varies depending on the amount of lime that is added and the environmental conditions, but generally ranges between 2%-5%. This process occurs immediately after adding the lime.
2- Modification of the soil: When lime is added to the soil, the distribution of the loads on the surface of the clay particles are modified, bringing about an ionic interchange between the Sodium (Na) in the soil and the Calcium (Ca) in the lime. This process also occurs immediately after the addition of the lime. The result is that the soil loses its water retaining properties.
3- Soil stabilization: In this case the effect is produced more or less gradually over the medium-term. When clay soils (that contain silica and alumina) come into contact with lime they can form calcium silicate and alumina hydrates. This reaction is called “pozzolanic” and brings about an increase in the simple compaction of the soil, as well as a higher level of stability under freezing conditions.
Which soils can be stabilized with lime?
Before undertaking any work on a soil, it is essential to know the exact characteristics of its constituent materials beforehand, as well as the problems typically associated with these materials.
So that the stabilization of soil with lime is successful, soils must be plastic (that is with a Plasticity Index equal to or greater than 10), but there are also other limitations concerning the types of soil that can be treated with this method of stabilization:
Therefore, the stabilization of soils requires an in-depth study beforehand, not only to define the characteristics and homogeneity of the soil, but also to determine the quantity of lime necessary, which is calculated in laboratory tests.
Calcinor in the stabilization of soils
Calcinor supplies a wide-range of products aimed at the stabilization of clay soils through the application of lime. They are all part of the STABYCAL® range, a product suitable for the three effects mentioned above.
|Modified property||Quicklime / STABYCAL®||Calcium Hydroxide / STABYCAL S®|
The technical department at Calcinor can also provide a complete assessment when carrying out soil stabilization. Contact us by clicking here.