Decrease in Shrinkage Limit
- Lime treatment of soil helps to decrease the shrinkage limit. Shrinkage limit is defined as the minimum water content at which a reduction in volume of soil mass ceases. It represents the lower limit of moisture content at which the soil starts to shrink on drying.
- Lime has the ability to stabilize the soil by reducing its plasticity. It reacts with the clay minerals present in the soil, causing the formation of calcium silicates and calcium aluminates. These compounds help to bind the soil particles together and reduce the shrinkage potential of the soil. As a result, the shrinkage limit of the soil decreases.

Increase in Plastic Limit
- Lime treatment also leads to an increase in the plastic limit of the soil. The plastic limit is the water content at which the soil becomes plastic and starts to deform under a certain amount of pressure.
- Lime acts as a binder and increases the plasticity of the soil. It helps in the flocculation of clay particles, which reduces the water content required to achieve a plastic state. Therefore, the plastic limit of the soil increases after lime treatment.

Decrease in Liquid Limit
- Contrary to what is stated in the question, lime treatment does not decrease the liquid limit of the soil. The liquid limit is the water content at which the soil changes from a liquid to a plastic state.
- Lime treatment does not have a direct effect on the liquid limit of the soil. However, it indirectly affects the liquid limit by reducing the plasticity index of the soil. The plasticity index is the difference between the liquid limit and the plastic limit. As lime treatment increases the plastic limit, the plasticity index also increases, but the liquid limit remains unchanged.

Flocculation of Clay Particles
- Lime treatment causes the flocculation of clay particles. Flocculation refers to the aggregation of clay particles into larger clumps or aggregates.
- Lime reacts with the clay minerals and forms flocculating agents, which promote the formation of stable clay aggregates. These aggregates help to improve the stability and strength of the soil. Flocculation also reduces the plasticity and shrinkage potential of the soil. Therefore, lime treatment is effective in promoting the flocculation of clay particles.

In conclusion, the correct statements are 2, 3, and 4. Lime treatment of soil leads to an increase in the plastic limit, a decrease in the liquid limit, and the flocculation of clay particles. However, the shrinkage limit of the soil decreases, not increases, after lime treatment.