AASHTO T90-00 pdf free download

AASHTO T90-00 pdf free download.Determining the Plastic Limit and Plasticity Index of Soils.
4. SAMPLE
4.1. If the plastic limit only is required, take a quantity of soil with a mass of about 20 g from the thoroughly mixed portion of the material passing the 0.425-mm sieve, obtained in accordance with T 87 or T 146. Place the air-dried soil in a mixing dish and thoroughly mix with distilled or dernineralized water until the mass becomes plastic enough to be easily shaped into a ball. Take a portion of this ball with a mass of about 8 g for the test sample.
Note 2—Tap water may be used for routine testing if comparative tests indicate no differences in results between using tap water and distilled or demineralized water. However, referee or disputed tests shall be performed using distilled or deniineralized water.
4.2. If both the liquid and plastic limits are required, take a test sample with a mass of about 8 g from the thoroughly wet and mixed portion of the soil prepared in accordance with T 89. Take the sample at any stage of the mixing process at which the mass becomes plastic enough to be easily shaped into a ball without sticking to the fingers excessively when squeezed. If the sample is taken before completion of the liquid limit test, set it aside and allow to season in air until the liquid limit test has been completed. If the sample taken during the liquid limit test is too dry to permit rolling to a 3-mm thread, add more water and remix.
5. PROCEDURE
5.1. Select a 1.5- to 2.0-g portion from the mass of soil taken in accordance with Section 4. Form the selected portion into an ellipsoidal mass.
5.2. Use one of the following methods to roll the soil mass into a 3-mm diameter thread at a rate of 80 to 90 strokes per minute, counting a stroke as one complete motion of the hand forward and back to the starting position again.
5.2.1. Haiicl Rolling Method—Roll the mass between the palm or fingers and the ground-glass plate (or a piece of paper laying on a smooth horizontal surface) with just sufficient pressure to roll the mass into a thread of uniform diameter throughout its length. The thread shall be further deformed on each stroke so that its diameter reaches 3 mm. taking no more than two minutes. The amount of hand or finger pressure required will vary greatly, according to the soil. Fragile soils of low plasticity are best rolled under the outer edge of the palm or at the base of the thumb.
5.2.2. Alternate Procedure, Plastic Limit Device Method—Place the soil mass on the bottom plate. Place the top plate in contact with the soil mass. Simultaneously apply a slight downward force and back and forth motion to the top plate so that the plate comes in contact with the side rails within two minutes. During this rolling process, do not allow the soil thread to contact the side rails.
Note 3—In most cases, more than one soil mass (thread) can be rolled simultaneously in the plastic limit rolling device.AASHTO T90-00 pdf download.