19
To set a new value, press
MAIN MENU, F2
(SETUP),
F4
(SET TARGETS),
F1
.
The LWD value then is flashing, Press
F3
to
INCREASE
or
F4
to
DECREASE
the value.
3.4 Site Selection
In general, all measurement should be made as soon as possible after the
site has been compacted. This is particularly true for fills and embankments
since evaporation may dry out the surface material and lower the average
moisture measurement. Any rain prior to the measurements may increase
these values unless sufficient time has elapsed to allow surface drying.
These conditions may be alleviated by removing surface materials to a
depth necessary to eliminate non-homogeneous materials.
For asphaltic concrete emplacements, the testing should ideally be made
while the material is being compacted so that additional rolling can be
accomplished before the material cools below acceptable compaction
temperatures.
The selection of a site to be measured is left to the judgement of the
operator or may be defined by prescribed procedures or specifications.
A random sampling method is recommended.
An optionally selected site should not be chosen on obvious conditions
which may either reject or pass the results It should be representative of the
total area to be tested.
3.5 Site Preparation
Any site to be measured should be clear of all loose debris before
attempting to seat the gauge. After removing the loose material from soils,
the area should be leveled using Scraper Plate to provide a flat surface.
Any large surface void areas should be filled with native fines even though
a direct transmission measurement will be made.
If hard surfaced areas are involved which make the direct transmission
method impractical or impossible, then a backscatter measurement will
have to be made. In addition, the surface voids must be carefully leveled
with mineral filler and lightly compacted with the Scraper Plate to minimize
surface errors.
The Scraper Plate is used as a guide for the Drill Rod to facilitate making a
vertical hole. Place the Scraper Plate over the desired site and while holding
it in place with one foot, drive the rod to a depth at least 50 mm (2 inches)
deeper than the measurement depth. The Drill Rod is marked in 50mm (2-
inch) increments to aid in judging the depth. Safety Glasses must be worn to
prevent eye damage while striking the rod with the hammer.
If the rod cannot be easily removed from the hole, place the Extraction Tool
around the rod and engage the flat surfaces at the bottom of the head.
Using the tool, rotate and pull on the rod to remove it. If the rod is still
difficult to remove, lightly tap on the bottom surface of the Extraction Tool
and drive it vertically out of the hole.
