The moisture content at the phase wherein the state is transitioning from plastic to liquid state. ATTERBERG LIMIT

The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit.

The moisture content at which the soil changes from a plastic state to a liquid state is known as the Liquid Limit (LL).

Here are the steps to determine the Liquid Limit:

1. Prepare the soil sample by air-drying it and breaking it down to pass through a 425-micron sieve.

2. Take about 120 grams of the soil sample and mix it with distilled water in a mixing dish until it becomes a uniform, plastic paste.

3. Place a portion of the soil paste into the cup of the liquid limit device. Spread the soil in the cup, making sure the grooving tool can cut a groove of standard dimensions in the soil.

4. Using the grooving tool, cut a groove in the soil sample.

5. Rotate the crank at a rate of two revolutions per second, allowing the cup to fall under the influence of gravity.

6. Count the number of blows until the two halves of the soil cake come into contact at the bottom of the groove along a distance of about 12 mm.

7. Repeat the test with different water contents to establish a range of moisture contents and corresponding numbers of blows.

8. Plot the moisture content against the logarithm of the number of blows on semi-log graph paper.

9. The liquid limit is the moisture content corresponding to 25 blows as read from the graph.

Remember, the liquid limit is an important water content limit of soil. It is used in soil classification to distinguish between different fine-grained soils for engineering purposes.