Method for testing methylene blue value of fine aggregate

Abstract

The invention discloses a method for testing a methylene blue value of fine aggregate. The method comprises the following steps: preparing a standard methylene blue solution with the concentration of 1g / L; determining a characteristic peak of the methylene blue solution; establishing a standard curve of the concentration and absorbance of the methylene blue solution; weighing a to-be-detected sample, mixing the to-be-detected sample with the methylene blue solution, standing to obtain a mixed solution after mixing, and diluting a supernatant liquid of the mixed solution to obtain a to-be-detected solution; and calculating the methylene blue concentration of the to-be-detected solution through the standard curve, finally calculating the mass of the methylene blue adsorbed by the fine aggregate, and determining the methylene blue value of the fine aggregate. According to the method, on the basis of a spectrophotometric method, the methylene blue adsorption condition of the fine aggregate is represented by the absorbance measured by a spectrophotometer so that the influence of human factors on a test result is effectively reduced, and the repeatability of the test is ensured; and according to the test method, the tested test data is more accurate and credible, the operability is high, the distinction degree of different fine aggregates is more remarkable, and rapid, accurate and quantitative evaluation can be achieved.

Description

technical field [0001] The invention relates to the field of road engineering testing, in particular to a method for testing the methylene blue value of fine aggregates. Background technique [0002] In the "Highway Engineering Aggregate Test Regulations" (JTG E42-2005), the fine aggregate methylene blue test is used to determine whether there is swelling clay mineral in the fine aggregate and determine its content. The specific operation steps can be summarized as follows: "preparing 10g / L methylene blue solution"; "stirring for 5 minutes to make fine aggregate suspension"; "adding 5mL methylene blue solution and stirring for 1min"; "color halo test (if any If the color halo disappears, proceed to the next step; if it does not appear, return to the previous step)"; "Keep stirring the suspension, and conduct a color halo test every 1 minute"; "If the color halo disappears within 4 minutes, then add 5mL sub methylene blue solution; if the color halo disappears in 5 minutes, ...

AI Technical Summary

Problems solved by technology

[0003] The analysis of the fine aggregate methylene blue test process has the following main defects: 1. The test operation process is cumbersome. In order to ensure that the suspended drops taken in the color halo test are representative, the fine aggregate should be as uniform as possible. Therefore, it is necessary to keep stirring during the test until the end of the test; 2. The accuracy of the test results is low, and it is greatly affected by human influence. The main performance is that methylene blue solution is added to the suspension every time during the test. 5mL, and take a stable light blue halo of about 1mm around the sediment as the titration end point; 3. The test process takes a long time, the fine aggregate suspension is prepared for 5 minutes, the methylene blue solution is added for at least 1 min, and the halo test is at least 1 min. 5 minutes, and the total time is at least 11 minutes. If there are more expansive clay minerals in the fine aggregate sample, it will take longer; 4. There is a lot of waste liquid produced during the test, and the volume of the prepared fine aggregate suspension is greater than 500mL. After adding methylene blue solution therein, it all becomes waste liquid to be treated and needs to be specially treated (methylene blue can form double salts with most inorganic salts; the aqueous solution is alkaline; low toxicity, avoid skin and eye contact)

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