Site Preparation
Asphalt Surface Preparation
It is possible, but usually not necessary, to take direct
transmission readings on asphalt. Drilling a hole in asphalt can
be difficult and may require the use of a proper drill (not the
drill rod) if the asphalt has cooled and hardened. Under normal
conditions, a backscatter reading provides an accurate
measurement of asphalt density Prepare the site as follows.
1. Find a smooth location on the asphalt. You may want to fill
the voids on open mixes with sand or cement. Take care to
leave the asphalt exposed. The gauge base must rest on the
asphalt, not the fill material!
2. Ensure that the gauge does not “rock.” It must remain steady.
If rocking occurs, find a more suitable test site. If taking a
measurement around a core, the gauge may be moved up to a
few inches to any side of the hole.
NOTE:
These directions also apply to taking a backscatter
measurement on soil.
Soil and Base Course Preparation
1. Locate a level site free from any large holes, cracks, or debris
(soil surface conditions are critical to accurate
measurements).
2. Smooth the surface by moving the scraper plate in a back-
and-forth motion. Filler such as fine sand may be used to
fill in the surface voids.
3. For direct transmission measurements, put the drill rod
through the extraction tool and then through one of the
guides on the plate (see Figure 5).
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