Methylene Blue Index for Clay

Experiment Name: Methylene Blue Index

Aim of the Experiment: Measurement of the adsorption of methylene blue dye by clay

Referred Standards: ASTM C837 - 09 (Reapproved 2014) - Standard Test Method for Methylene Blue Index of Clay.

Summary of Test Method:

·         2 gram of oven dried clay sample to be mixed in 300 ml of distilled water taken in 600 ml beaker.

·         If required pH of the slurry to be maintained between 2.5 to 3.8 by addition of Sulphuric acid and slurry to be stirred for 10 to 15 minutes.

·         Methylene blue solution to be prepared by dissolving 1 g of methylene blue in distilled water to produce 200 ml of solution.

·         5 ml of methylene blue solution from burette to be added to slurry and stirred for 2 minutes.

·         A drop of the slurry to be taken and placedon the edge of the filter paper and appearance of the drop to be observed.The end point is indicated by the formation of a light blue haloaround the drop.

·         Addition of the methylene blue solutionto the slurry to be continued in 1.0-mL increments with 1 to 2 min of stirringafter each addition, then testing, until the end point is reached.

Significance and Use:

·         Tests run on many clays generally indicate that astraight-line relationship exists between the methylene blueindex (MBI) and fundamental clay propertiessuch as cationexchange capacity, dry bond strength, and casting rate.

·         When the colloidal portion of the clay is kaolinite, there is adirect correlation of adsorption with specific surface (as determined bynitrogen adsorption).

·         When the colloidal portion containssignificant amounts of illite or montmorillonite, the same closecorrelation does not exist.

Observations and Calculations:

·         Volume of methylene blue solution required to form blue halo ring (ml) = 10

·         Methylene Blue Index (MBI) = [(E*V)/W]*100= [(0.01*10)/2]*100 = 5

Where, MBI = methylene blue index for the clay in meq/100 g clay,

E = milli-equivalents of methylene blue per ml

V = methylene blue solution required forthe titration (in ml)

W = weight of dry material (in grams).

Results:

·         The methylene blue index for the clay is found to be 5.

Discussion:

·         The MBI value we get here in the experiment is 5, which indicates towards the excellent expected performance of aggregate in pavement.

·          But we have not followed the complete procedure due to unavailability of pH meter, which was necessary to know about the pH of slurry and to maintain the acidic range of the slurry.

·         That is why we cannot be sure about the reliability of the test results.