2.2. Plasticity and Structure of Soil (Plastic Limit)

Question 1

The plastic limit is defined as the moisture content in percent, at which the soil crumbles, when rolled into threads of 3.18 mm (1/8 in.) in diameter.

Answer 1

Rolling into Thread Method (ASTM D-4318)

Question 2

Similar to Liquid Limit test only the weight of the cone is 2.35 N (240 grams) instead of 0.78 N (80 grams), three times heavier.

Answer 2

Fall-Cone Method

Question 3

Testing Organic Matter in Soil: The liquid limit comparison before and after oven-drying can be used as a qualitative measure of organic matter content in soil.

Answer 3

Comparison of Liquid Limits

Question 4

Testing Organic Matter in Soil: The plastic limit test is performed on material prepared for the liquid limit test to assess soil consistency.

Answer 4

Plastic Limit Test

Question 5

Testing Organic Matter in Soil: The multipoint liquid limit method is generally more precise than the one-point method for determining soil liquid limits.

Answer 5

Multipoint Liquid Limit Method

Question 6

Testing Organic Matter in Soil: The one-point method’s correlation may not be valid for certain soils, such as organic soils or soils from a marine environment; the multipoint method is recommended in these cases.

Answer 6

Limitations of One-Point Method