Plastic 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)
1. SCOPE
1.1. The plastic limit of a soil is the
lowest moisture content at which the soil remains plastic. The plastic index of
a soil is the range in moisture content, expressed as a percentage of the mass
of the oven-dried soil, within which the material is in a plastic state. The
plasticity index is calculated as the numerical difference between the liquid
limit and plastic limit of the soil.
1.2.
The following applies to all specified limits in this standard: For the
purpose of determining conformance with these specification, an observed value
or a calculated value shall be rounded off" to the nearest unit" in
the last right-hand place of figure used in expressing the limiting value, in
accordance with ASTM E29.
1.3. Two procedures for rolling out soil
samples are provided in this method: the Hand Rolling Method and the plastic
Limit Device Method. The Hand Rolling Method shall be used as the referee
procedure.
1.4. The test method is often conducted in
conjunction with T89, which is used to determine the liquid limit of soils.
2. REFERENCED DOCUMENTS
2.1. AASHTO Standards
M 231, Weighing Devices Used in the
Testing of Materials
R 18, Establishing and Implementing a
Quality Management System for Construction Materials Testing Laboratories
R 58, Dry Preparation for Disturbed Soil
and Soil-Aggregate Samples for Test
R 61, Establishing Requirements for
Equipment Calibration, Standardizations, and Checks
R 74, Wet Preparation of Disturbed Soil
Samples for Test
T 89, Determining the Liquid Limit of Soils
T 265, Laboratory Determination of
Moisture Content of Soils
2.2. ASTM Standard:
E29, Standard Practice for Using
Significant Digits in Test Data to Determine Conformance with Specifications
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