FIELD MANUAL For HOT MIX ASPHALT (HMA) - Mississippi ...

5.6.1.3 Thoroughly break up the mixture and cool to ambient temperature, using
care not to fracture the mineral particles, so that the particles of the fine-aggregate
portion are not larger than 1/4-inch in diameter. The mixture is easiest to break apart
after a brief cooling period while it is still warm. A portable electric fan may be
used to speed the cooling process.
5.6.1.4 Calibrate metal bowls by weighing under water using the bowl option. The
volume of the metal bowls may not be measured using the pycnometer method.
5.6.1.5 Place the entire amount of each sample in appropriate container and weigh
to the nearest 0.1 gram. Add water at 77±2ºF to cover the sample by 1-1/4 to 2
inches. A few drops of a dilute (10%) liquid detergent (such as Joy or equivalent),
to act as a wetting agent, may be added to the water to facilitate the release of
entrapped air.
5.6.1.6 Remove entrapped air by subjecting the contents of the container to a partial
vacuum which will result in 30 mm Hg or less absolute pressure for 15±2 minutes.
Check the residual pressure in the container using a gage or closed end manometer
with an accuracy of ± 3 mm, attached independently to the container. The container
and contents shall be shaken vigorously at intervals of about two (2) minutes in
order to assist the removal of air bubbles. A mechanical shaker may be used if test
results are available from the Contractor that demonstrate that results approximately
equal to hand shaking can be obtained (±0.008). If the mixture is exposed to air after
the vacuum is released, the test results are invalid and the vacuum procedure must be
conducted again.
5.6.1.7 Volume Determination
5.6.1.7.1 Flask - Fill flask with water taking care to avoid adding air bubbles during
this process (causes a low value of G mm ). Adjust the temperature of the added water
such that the temperature of the water in the flask is 77±2ºF. Check the temperature
of the water in the flask and weigh 10±1 minutes after the completion of the vacuum.
Calculate the G mm to three decimal places as follows:
Without Dry Back Correction:
G mm =
A
A+
D − E
With Dry Back Correction:
G mm =
A
A1+
D − E
Rev. February 5, 2007 30