AASHTO T 90-15 pdf free download

AASHTO T 90-15 pdf free download.Determining the Plastic Limit and Plasticity Index of Soils.
4. CALIBRATIONS, STANDARDIZATIONS, AND CHECKS
4.1. Unless otherwise specified, follow the requirements and intervals for equipment calibrations, standardizations, and checks in R 18.
4.2. Follow the procedures for performing equipment calibrations, standardizations, and checks found in R 61.
5. SAMPLE
I/on/v the plastic limit is to be determined—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 (No. 40) sieve, obtained in accordance with R 58 or T 146. Place the air-dried soil in a mixing dish and thoroughly mix with distilled or demineralized water until the mass becomes plastic enough to be easily shaped into a ball (Notes 2 and 3). Take a portion of this ball with a mass of about 10 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, use distilled or demineralized water for referee or disputed tests.
Note 3—The objective is to add enough moisture to a plastic soil sample so that the 3-mm thread described in Section 6 does not crumble on the first roll. For a nonplastic soil, this will not be possible.
5.2. If the plasilcitv index (both liquid and plastic li,iiiO is to be determined—Take a test sample with a mass of about 10 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 as described in Section 6, add more water and remix (Note 3).
6. PROCEDURE
6.1. Determine and record the mass of the moisture content container.
6.2. Select a 1.5- to 2.0-g portion from the 8-g mass of soil prepared in accordance with Section 5. Form the selected portion into an ellipsoidal mass.
6.3. 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.
6.3.1. hand Rolling Method—Roll the mass between the palm or fingers and the ground-glass plate or unglazed paper with just sufficient pressure to roll the mass into a thread of uniform diameter throughout its length. Deform the thread further on each stroke until its diameter reaches 3 mm. Take no more than 2 mm to roll the soil mass to the 3-mm diameter.
Note 4 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.
6.3.2. 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 the plate comes in contact with the side rails within 2 mm. During this rolling process, do not allow the soil thread to contact the side rails.
Note 5—In most cases, more than one soil mass (thread) can be rolled simultaneously in the plastic limit rolling device.AASHTO T 90-15 pdf download.