Factors affecting Soil cement – The various factors, which affect soil cement, are:
- Type of Soil
- Quality of cement
- Quantity of water
- Mixing, compaction and curing
The suitable materials must be pulverisable. They, in general, comprise granular materials with sufficient fines. Such material requires less cement. In materials, which contain deficiency in fines require more cement but they are also fall under suitable materials.
The cement requirement depends upon the gradation of the soil. A well graded soil requires about 5 % cement, whereas a poorly graded, uniform soil may require about 9 % cement. Non-plastic silts require about 10 % cement, whereas plastic clays may need about 13 % cement. The actual quantity required shall have to be ascertained by carrying out laboratory tests.
Water requirement should be sufficient for cement hydration and good workability. Generally the amount of water ascertained by compaction requirement is adequate for cement hydration as well. Potable water is most desirable.
In the soil cement, the ingredients are mixed thoroughly in order to make it more stable. Otherwise non-homogeneous weak product results. After it is compacted well as in the case of soil, addition of admixtures such as lime, calcium chloride, fly ash, sodium carbonate, sodium sulfate reduces the cement requirement.
In lime stabilization the soil is stabilized by adding lime. By this method clayey soil is stabilized well. When lime is added to soil, it reacts with the soil and cations are exchanged in the diffused double layer. As a result plasticity is reduced significantly and the resulting material becomes more friable than the original clay. Consequently the material is therefore more suitable as sub grade. The amount of lime required for stabilization varies between 2 to 10 %. For a rough guide the following amount of lime may be used.
For clayey gravel having less than 50 % of silt-clay fraction 2 to 5 % of lime may be required. If the silt-clay fraction in soil exceeds more than 50 %, 5 to 10 % of lime may be used. For heavy clay the amount of lime required is about l0 %. The lime stabilization is not suitable for stabilization of sands.