Organic Impurities in Fine Aggregates for Concrete Standard Specification for AASHTO DESIGNATION: T 21-91 (1996)! 1. SCOPE @© 11 Aste method covers the pro: cedure for an approximate determination of the presence of injurious organic com- pounds in fine aggregates that are to be used in cement mortar or concrete 1.2 This standard may involve haz- ardous materials, operations, and equip- ment. This standard does not purport to address all of the safety problems associated with its use. Iti the responsi bility of whoever uses this standard to ‘consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. © 2» nzrmencen vocumesrs 21 AASHTO Standard: M6 Fine Aggregate for Portland Cement Concrete T2_ Sampling Aggregates TTL Effect of Organic Im- purities in Fine Ag- ‘gregate on Strength of Mortar T 248 Reducing Field Sam- ples of Aggregates to Testing Size 22. ASTM Standards: D 1544 Test for Color of Transparent Liquids (Gardner Color Scale) Tie rr agree wit ASTM. C 4092, except fer siting of ext betwen Seton 9.2 tnd $2 (ASTM DESIGNATION: C 40-92) 3. SIGNIFICANCE AND USE 3A This test method is of si cance in making a preliminary determi- nation of the acceptability of fine aggre- gates with respect to the requirements of M6. 32. The principal value of this test method is to furnish a warning that or- ganic impurities may be present. When 1 sample subjected fo this test produces a color darker than the standard color solution (see Section 5.2), it is advisable to perform the test for the effect of o- ganic impurities on the strength of mortar in accordance with T 71 4, APPARATUS 4.1 Glass Bottles—Twelve of 16-07 (US. fluid) (approximately 350 or 470 mL) nominal capacity colorless glass graduated bottles of approximately oval cross section, equipped with watertight stoppers or caps, not soluble in the speci- fied reagents. In no case shall the maxi- ‘mum outside thickness of the bottles, ‘measured along the line of sight used for the color comparison, be greater than 2" in. (60 mm) or less than 1.5 in, (40 mm). The graduations on the botdes shall be in ounces (USS. fluid), or milili- tres, except that unmarked bottles may bbe calibrated and scribed with gradua- tions by the user. In such case, graduation ‘marks are required at only three points as follows: 41.1 Reference Color Solution Level—2'/, 02 (US. fluid) (75 mL), 41.2 Fine Aggregate Level—<'/; 02 (US. fluid) (130 mL), and 41.3 NaOH Solution Level—T 02 (US. fluid) (200 mL). 8, REAGENT AND REFERENCE STANDARD COLOR SOLUTION 5.1 Reagent Sodium Hydroxide So- lution (3 percent}—Dissolve 3 parts by ‘weight of sodium hydroxide (NaOH) in 97 parts of water. 52. Reference Standard Color Solu- sion—Dissolve reagent grade potassium dichromate (K;Cr0;) 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 com- parison using gentle heat if necessary to effect solution. Preparation of the refer- cence standard color solution is unneces- sary when the altemative procedure used to determine the color value, 6. SAMPLING 6.1 The sample shall be selected in general accordance with T 2, 7. TEST SAMPLE 7A Obtain a test sample of fine ag- _gregate weighing about 1 pound (approx- imately 450 grams) in accordance with ‘T 248. Sample drying prior to testing, if necessary, shall be done by air dry: ing only. PROCEDURE, 8.1 Fill a glass botle to the 4! fluid 02 (approximately 130-mL) 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 B4 METHODS OF SAMPLING AND TESTING Ta aggregate and liquid, indicated after shaking, is 7 fluid oz (approximately 200 mL). 83 Stopper the bottle, shake vigor- ‘ously, and then allow to’stand for 24 hours. 9. DETERMINATION OF COLOR VALUE 9.1 Standard Procedure—At the end of the 24-hour standing period, fill a glass bottle to the 2',-fluid oz (approxi- mately 75-mL) level with the fresh refer~ fence standard color solution, prepared rot longer than 2 hours previously, as prescribed in Section 5.2. Then compare the color of the supernatant liquid above the test sample with that ofthe reference standard color solution and record whether it is lighter, darker, or of equal color to that of the reference standard. Make the color comparison by holding the two bottles close together and looking through them. 92 Alternative Procedure—To de- fine more precisely the color of the liquid of the test sample, five glass standard ‘colors may be used as described in Table 1 of ASTM D 1544, using the follow- ing colors: Gardner Color Standaré No, Organi Plate No. 5 1 8 2 " 3 (standard) 1“ 4 16 5 ‘The comparison procedure described in Section 9.1 shall be used, except that the organic plate number which is nearest the color of the supernatant liquid above the test specimen shall be reported. NOTE 1—A svitble instrument consists fof the glass color standards mounted in a plastic holder. The instrument is provided ‘with all five organic plate number colors. 10, INTERPRETATION OF RESULTS 10.1 If the color of the supematant liquid is darker than that of the reference standard color solution, the fine aggre- gate under test shall be considered to possibly contain injurious organic com- pounds, and further tests should be made before approving the fine aggregate for use in concrete. 11. PRECISION AND BIAS U1. Since this test produces no nu- ‘merical values, determination of the pre- cision and bias is not necessary.