Standard Test Method for Rapid Determination of the Methylene Blue Value for Fine Aggregate or Mineral Filler Using a Colorimeter
5.1 This test method is used to determine rapidly the amount of methylene blue adsorbed by a specimen of fine aggregate or mineral filler. The result is reported as a methylene blue value in units of mg of methylene blue adsorbed per g of fine aggregate or mineral filler. The methylene blue value is a function of the amount and characteristics of clay minerals present in the test specimen. High methylene blue values indicate increased potential for diminished fine aggregate or mineral filler performance in a cementitious mixture due to the presence of clays.
Note 1: Results from this test method are not expected to be correlated with those obtained using AASHTO T 330 or EN 933-9. These three test methods are likely to give very different numerical values even though the units are the same. The AASHTO T 330 test is performed only on the fraction of an aggregate passing the 75 μm sieve, the EN 933-9 test is performed only on the fraction finer than 2 mm, and this test is performed on the fraction finer than the 4.75 mm sieve. Therefore, when testing the same fine aggregate source, the AASHTO test method would give the highest methylene blue value because any clay present in the specimen would be concentrated in the fraction finer than the 75 μm sieve. The AASHTO and EN test methods do not take into account the amount of material passing the 75 μm sieve or 2 mm sieve, respectively. For example, a fine aggregate with high methylene blue value measured by the AASHTO method but low percentage passing the 75 μm sieve may have less effect on concrete performance than a fine aggregate with low methylene blue value measured by the AASHTO method but a high percentage passing the 75 μm sieve. In contrast, this test method expresses methylene blue value based on the entire fine aggregate or mineral filler specimen. Additionally, the AASHTO and EN test methods use titration to determine the amount of methylene blue of known concentration that is adsorbed by a specimen and require the operator to visually determine the end point of the test. In contrast, this test method uses a colorimeter to detect the change in concentration of methylene blue solution before and after being mixed with the fine aggregate or mineral filler specimen.
Note 2: Recommendations for maximum methylene blue values for specific applications are not provided in this test method. Maximum methylene blue values should be established based on successful performance of fine aggregate or mineral filler in the applications under consideration.
1.1 This test method provides a rapid test to determine the amount of methylene blue adsorbed by a specimen of fine aggregate or mineral filler and can be used both in the laboratory and in the field.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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