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Follow the procedures outlined below to prepare asphalt samples
for gauge calibration.
Preparing Blank Samples
Before preparing calibration samples, prepare a blank sample of
aggregate to estimate the asphalt sample size or to adjust the
calibration for changes in aggregate size or moisture content.
1. Obtain enough sample of the aggregate(s) being used in the
asphalt mixture for a minimum of three samples. For each
calibration sample, obtain a minimum of 9 kg (20 lbs) of
aggregate. Refer to AASHTO Standard Method T2.
2. Obtain a sample of the liquid asphalt (bitumen) being used
in the mixture. For each calibration sample, obtain at least
1.4 kg (3 lbs). Refer to AASHTO Method T168.
3. Blend the aggregate(s) in the proper proportions (or obtain
blended aggregate samples). The aggregate should be
maintained at the proposed plant temperature or placed in
an oven and baked for 3 hours at 121C (250F) to remove
any moisture.
4. Select an empty sample pan and obtain the weight (tare
weight) using a balance or electronic scales.
5. Fill the sample pan about half-full with dry, hot aggregate
(see Figure 3).
6. Settle the aggregate by dropping the pan about one inch
onto a hard surface several times.
7. Smooth the aggregate mixture into the corners of the pan.
8. Fill the rest of the pan with aggregate, overfilling slightly.
9. Scrape off the surface with the straightedge.
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