The sample we like to test should be ground to make powder that will pass standard test 75 µm. Dear reader we like to recall that Methylene blue is organic dyeing agent, used to determine clay minerals; here for concrete aggregates. We have already introduced this dyestuff.
Of this powdered simple, 1 gm is taken and dispersed in water and then titration is done with Methylene blue. The information we have missed are:
a. Volume of water is 30 ml to disperse sample
b. In titration process each 0.5 ml Methylene blue is added as solution
c. The solution of methylene blue is prepared by dissolving 0.1gm Methylene blue into 200 ml of de-ionized and distilled water.
For each addition, the color is examined under sunlight, at the end of titration a circular band of pale blue is observed. The amount of Methylene blue is recorded to produce such color and our test is completed.
Now we have to interpret MBV (Methylene blue value) which is express as
Where, V= Titrated volume of Methylene blue added to suspension and
M=Mass of tested portion of powder
Now what does titration means?
Titration means there have no clay particles to absorb Methylene blue and blue color is appeared. This test method is used in France as standard test but has limited experience.
Now some limits about this test-
According to Department of Environment (Northern Ireland)-
For basalt 1 .0 %
gritstone aggregate 0.7 %
The advantage of this test is it requires simple and usual chemical apparatus. Disadvantage is there should have a rock grinder to make powder of aggregate sample as discussed above.