What are the three primary numbers obtained from Atterburg limits testing?

The three primary numbers obtained from Atterberg limits testing are indeed the liquid limit, plastic limit, and plasticity index. The liquid limit is the water content at which soil changes from a plastic state to a liquid state, providing insight into the soil's behavior under various moisture conditions. The plastic limit is the water content at which soil transitions from a semi-solid to a plastic state, indicating the point at which the soil starts to exhibit plasticity.

The plasticity index, which is derived from the difference between the liquid limit and the plastic limit, represents the range of moisture content over which the soil behaves plastically. This property is crucial for understanding the workability, stability, and potential for shrink-swell behavior of the soil, key factors in geotechnical engineering and construction.

While the other options mention various soil properties and limits, they do not align with the specific parameters defined by the Atterberg limits testing. These parameters are fundamental for characterizing fine-grained soils, particularly those with significant clay content, which influence construction practices and soil management.