Watch for suspicious readings
If a reading seems unusual or suspicious, check for possible measurement
errors (dirty surface, wet surface, low battery voltage) and retake the reading.
Best results are obtained when moisture levels for a series of readings are kept
relatively constant. If the moisture level for a reading is more than a percentage
point higher or lower than the previous readings, the reading should be treated as
suspicious
Don’t touch the PQI while it is making a measurement
Touching any part of the PQI while it is performing a measurement can distort
the reading.
Choose measurement spots with a relatively smooth surface area (avoid
rough, segregated areas)
The PQI measures percentage of air voids in the area beneath the probe,
including the voids on the surface of the mat, while the AASHTO T-166 specific
gravity determination method ignores these voids. In order to better track what
the AASHTO T-166 method is measuring, PQI readings should be taken on
areas where there are relatively few surface voids. This is especially important
when the PQI is used on mixes containing larger aggregate.
Measurements should be made on the same day as paving
While the PQI has corrections algorithm for surface moisture, embedded
moisture which can occur after periods of rain, can adversely effect the PQI
readings. If you need to take PQI readings at exact coring locations and the cores
cannot be extracted until the day following paving, mark the spots and take the
PQI readings on the day of paving.
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Summary of Contents for PQI 301
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