STATE OF OHIO
DEPARTMENT OF TRANSPORTATION
SUPPLEMENT 1052
DETERMINATION OF METHYLENE BLUE ADSORPTION VALUE
OF MINERAL AGGREGATE FILLERS AND FINES
April 18, 2008
1052.1
Scope
This supplement covers the procedure for measuring the amount of potentially harmful fine
material (including clay and organic material) present in an aggregate.
1052.2
Equipment
Perform this test in a Level 3 laboratory, containing the following additional equipment:
a.
b.
c.
d.
e.
f.
g.
h.
i.
1052.3
a.
b.
1052.4
amber colored burette, mounted on a titration stand, with sufficient capacity to
completely perform the test
3 suitable glass beakers or flasks
magnetic mixer with stir bar
balance, sensitive to 0.01 gram, of sufficient capacity to perform the test
250 mm glass rod with an 8 mm diameter
laboratory timer or stop watch
75 μm (No. 200) sieve and pan
1000 ml volumetric flask
Whatman No. 2 filter paper
Reagents
Methylene Blue, reagent grade, dated and stored for no more than 4 months in a
brown bottle wrapped with foil in a dark cabinet, at lab temperature
distilled or deionized water at lab temperature
Procedure
Perform this test shall be performed on a sample of material passing the No. 200 (75 μm)
sieve, taken from the washed gradation of a 2000 g sample of the individual or combined
materials (as required). Dry the washed sample to a constant weight and mix thoroughly. Three
separate samples of 10 g (± 0.05 g) each are taken. Combine each of these samples with 30 g of
distilled water in a beaker by stirring with the magnetic stirrer until thoroughly wet and
dispersed.
1
Dissolve one gram of Methylene Blue in enough distilled water to make up a 200 ml
solution, with each 1 ml of solution containing 5 mg of Methylene Blue. Titrate the Methylene
Blue solution stepwise in 0.5 ml aliquots from the burette into the beakers containing the fine
aggregate solution, while continually stirring the fine aggregate solution, keeping the fine
aggregate in suspension. After each addition of the Methylene Blue solution, continue stirring
for 1 minute. After this, remove a small drop of the aggregate suspension and place on the filter
paper with the glass rod. Repeat successive additions of the Methylene Blue solution until the
end point is reached.
Initially, a well defined circle of Methylene Blue-stained dust is formed and is surrounded
with an outer ring or corona of clear water. The end point is reached when a permanent light
blue coloration or “halo” is observed in this ring of clear water. When the initial end point is
reached, continue stirring for five minutes and repeat the test to ascertain the permanent
endpoint. Continue small additions of Methylene Blue solution until the 5 minute permanent
end point is reached. The number of milligrams of Methylene Blue is calculated by multiplying
the number of milliliters of Methylene Blue (MB) by 5 mg/ml (ml MB × 5 mg/ml = mg MB).
The Methylene Blue Value (MBV) is reported as milligrams of Methylene Blue solution per
gram of fine aggregate (e.g. MBV = 55 mg/10g or 5.5 mg/g). Report multiple tests separately.
1052.5
Notes
a.
Certain clays will give poor results with this test. If so, soak the No. 200 (75 μm)
sieve material in the distilled water at 90 ̊C for three hours while stirring. Allow to
cool to lab temperature before proceeding with titration.
b.
With experience, the person performing the test can reach the end point quicker by
skipping early aliquots.
2