Standard Method of Test for Determining the Plastic Limit and Plasticity Index of Soils

Standard Method of Test for Determining the Plastic Limit and Plasticity Index of Soils

Standard Method of Test for Determining the Plastic Limit and Plasticity Index of Soils

AASHTO

AASHTO Designation: T 90-16

 

Technical Section: 1a, Soil and Unbound Recycled

Material

 

  Release: Group 3 (OCTOBER)

 

7.            CALCULATIONS

 

 7.1          The plastic limit of the soil is the moisture content determined in Section 6.7, expressed as a percentage of the oven-dry mass, and determined in accordance with T 265. Report the plastic limit to the nearest whole number.

7.2          If applicable, calculate the plasticity index of a soil as the difference between its liquid limit and its plastic limit, as follows:

 

Plasticity index= liquid limit – plastic limit

 

 7.3          Report the result as calculated in Section 7.2, as the plasticity index, except under the following condition:

 

 7.3.1         When the liquid limit or plastic limit cannot be determined, report the plastic index as NP (non plastic)

 

7.3.2         When the liquid limit is equal to, or greater than, the liquid limit, report the plasticity index as NP.

Calculation attach with graph in below figure

 

 

 

8.            PRECISION STATEMENT

 

8.1          This precision statement applies to soil with a plastic limit range between 15 and 32, tested using the hand rolling method.

 

8.2          Repeatability (Single Operator) --- Two result obtained by the same operator on the same sample in the same laboratory using the same apparatus should be considered suspect if they differ by more than 10 percent of their mean.

 

 

8.3          Reproducibility (Multilaboratory) --- Two result obtained by the different laboratories should be considered suspect if they differ from each other by more than 18 percent of their mean.