Effect of Lime on Swelling Soils

Introduction: Lime is commonly used to stabilize soil in construction projects. It can be added in different forms such as quicklime, hydrated lime, or lime slurry. Lime can improve the soil properties by modifying the clay minerals and reducing the water content. In this context, let's discuss the effect of lime on swelling soils.

Statement Analysis: The given statements are:

1. On addition of lime to swelling soils, their liquid limit increases
2. On addition of lime to swelling soils, their plastic limit increases
3. On addition of lime to swelling soils, their shrinkage limit increases
4. On addition of lime to swelling soils, their swelling potential decreases

Let's analyze each statement in detail.

1. Liquid Limit Increases: The liquid limit of a soil is the moisture content at which the soil changes from plastic state to liquid state. When lime is added to a swelling soil, it reacts with the clay minerals and forms new compounds. These compounds have a higher water holding capacity, which increases the liquid limit of the soil.

2. Plastic Limit Increases: The plastic limit of a soil is the moisture content at which the soil changes from semisolid state to plastic state. When lime is added to a swelling soil, it reduces the plasticity index of the soil. This means that the soil requires more water to attain plasticity, which increases the plastic limit of the soil.

3. Shrinkage Limit Increases: The shrinkage limit of a soil is the moisture content at which the soil undergoes maximum shrinkage. When lime is added to a swelling soil, it reduces the water holding capacity of the soil. This means that the soil requires more water to attain maximum shrinkage, which increases the shrinkage limit of the soil.

4. Swelling Potential Decreases: The swelling potential of a soil is the ability of the soil to swell when exposed to water. When lime is added to a swelling soil, it reduces the water holding capacity of the soil. This means that the soil can absorb less water and hence its swelling potential decreases.

Conclusion: From the above analysis, it is clear that statements 2, 3, and 4 are correct. Statement 1 is incorrect as the addition of lime to swelling soils increases the liquid limit. Therefore, option 'C' is the correct answer.