AASHTO T 21M pdf free download
AASHTO T 21M pdf free download.Organic Impurities in Fine Aggregates for Concrete.
3. SIGNIFICANCE AND USE
3.1. This test method is of significance in making a preliminary determination of the acceptability of fine aggregates with respect to the requirements of M 6.
3.2. The principal value of this test method is to furnish a warning that organic impurities may be present. When a sample subjected to this test produces a color darker than the standard color, it is advisable to perform the test for the effect of organic impurities on the strength of mortar in accordance with T 71.
4. APPARATUS
4.1. Glass Bottles—Colorless glass graduated bottles, approximately 240- to 470-mL (8- to 16-oz) nominal capacity, equipped with watertight stoppers or caps, not soluble in the specified reagents. In no case shall the maximum outside dimension of the bottles, measured along the line of sight used for the color comparison, be greater than 60 mm (2.5 in.) or less than 40 mm (1.5 in.). The graduations on the bottles shall be in milliliters or ounces (U.S. fluid), except that unmarked bottles may be calibrated and scribed with graduations by the user. In such case, graduation marks are required at only three points as follows:
4.1.1. Standard (‘olo,’ Solution Level—75 mL, (2’/2 oz) (U.S. fluid);
4.1.2. Fine Aggregate Level—130 mL, (4V2 oz) (U.S. fluid); and
4.1.3. NaOH Solution Level—200 mL, (7 oz) (U.S. fluid).
4.2. Glass (‘olor Standard:
4.2.1. Glass color standard shall be used as described in Table 1 of ASTM D1544.
Note 1—A suitable instrument consists of five glass color standards mounted in a plastic holder. Oniy the glass identified as Gardner Color Standard No. 11, corresponding to organic plate No. 3, is to be used as the glass color standard in Section 9.1.1.
5. REAGENT AND STANDARD COLOR SOLUTION
5.1. Regulatory information for the reagent and color solution can be found in 29 CFR 19 10.1200.
5.2. Reageiit Sodium Hydroxide Solution (3 percent) —Dissolve 3 parts by mass of sodium hydroxide (NaOH) in 97 parts of water.
5.3. Standard color So/ution—Dissolve reagent grade potassium dichromate (K2Cr2O7) in concentrated sulfuric acid (sp gr 1.84) at the rate of 0.250 g/100 mL of acid. The solution must be freshly made for the color comparison, using gentle heat if necessary to effect solution. Preparation of the reference standard color solution is unnecessary when the Glass Color Standard Procedure is used to determine the color value.
TEST SAMPLE
7.1. Obtain a test sample of fine aggregate of about 450 g (approximately 1 Ib) in accordance with
R 76. Sample drying prior to testing, if necessary, shall be done by air drying only.
PROCEDURE
Fill a glass bottle to the 130-mL (approximately 4V2-fluid oz) level with the sample of the fine aggregate to be tested.
8.2. Add a 3-percent NaOH solution in water until the volume of the fine aggregate and liquid, indicated after shaking, is 200 mL (approximately 7 fluid oz).
8.3. Stopper the bottle, shake vigorously, and then allow to stand for 24 h.
DETERMINATION OF COLOR VALUE
Glass C’olor &andard Procedure—At the end of the 24-h standing period, visually compare the color standards to the color of the supematant liquid above the test specimen. Report the organic plate number corresponding to the Gardner Color Standard number that is nearest the color of the supernatant liquid. When using this procedure, it is not necessary to prepare the standard color solution.AASHTO T 21M pdf download.
