What does a liquid limit test measure?

The liquid limit test specifically measures the water content at which a soil transitions from a plastic state to a liquid state. This transition is crucial for understanding the behavior of cohesive soils, particularly clay. In practical terms, it indicates the amount of moisture in soil required for it to behave more like a liquid than a solid or plastic material.

Understanding the liquid limit is essential for assessing soil properties such as plasticity and workability, which directly influence engineering decisions regarding soil stability, foundation design, and potential for expansion or contraction with moisture changes. The results of this test are used to classify soils under unified soil classification systems, helping engineers and inspectors determine appropriate construction methods and material handling strategies.

The other choices focus on different soil properties that the liquid limit test does not assess, further defining why this particular measure is critical in soil classification and behavior evaluation.