11
© 2012 by Proceq SA
4.1
Planning and preparation
In Canin
+
, the measurement data is stored in files called “Objects”. In order to make the evaluation
simpler it is recommended before beginning work to map out the site and assign various sections to
particular “Objects”. This will facilitate the evaluation in ProVista at a later stage.
In order to minimize the effort needed for the investigation, the site can be divided into sections that
are subjected to similar amounts of wear, by means of a visual inspection. (e.g. Multi-story car park:
Entrance area, traffic lane, parking areas, areas with and without cracks or obvious areas where
puddles form.) Following this inspection, representative sub-sections should be chosen, in which the
potential field measurements are carried out with the Canin
+
system.
4.2
Selecting the correct grid
One method is to use a relatively large grid for a first estimate, e.g. 0.50 x 0.50 m
2
up to a max of 1.0
x 1.0 m
2
using the coarse grid. (See 5.4).
Suspect areas can be further investigated using a finer grid (e.g. 0.15 x 0.15 m
2
), to identify as closely
as possible the extent of the surface that will require corrective maintenance.
Vertical elements usually require a smaller grid (e.g. 0.15 x 0.15 m
2
). The same applies to slender
elements, for which the grid will be defined by the geometry, (e.g. steps, beams and joints etc.).
For large horizontal surfaces (parking decks, bridge decks etc.) a grid of 0.25 x 0.25 m
2
to 0.5 x
0.5m
2
is typically sufficient.
4.3
Choosing the appropriate electrode
Depending on the surface under test, it is necessary to choose which type of electrode will be
employed. For small areas or areas that are difficult to access, the small and light Rod Electrode will
typically be used. For more accessible horizontal, vertical or overhead surfaces, it is much faster to
use the 1-Wheel Electrode. For large horizontal surfaces the 4-Wheel Electrode is recommended for
the reason of the significantly faster automatic measurement in a pre-defined grid.
4.4
Connect to the reinforcement
The ground cable must be connected to the reinforcement of the surface to be measured. This is
usually done by chiseling or drilling to the reinforcement. In some cases it may be possible to use
existing building elements that are connected to the reinforcement (e.g. water pipes, earth points).
The connection to the reinforcement should be made with the least possible resistance. To this end
it may be beneficial to grind the reinforcement with (e.g using an angle grinder) and to connect the
cable with welding tongs.
The connection should be tested for continuity. This requires at least one other point of the reinforce-
ment to be exposed and to check the resistance between the two with an Ohmmeter. The connec-
tions should be situated as far as possible in opposing corner areas of the surface under test. The
measured resistance should not be more than 1
Ω
above the resistance of the cable used.
4.5
Functional check of the instrument
Before real tests begin, a functional check is recommended (see section 11).
Additionally the probes should provide a stable value close to zero (typically E = ± 20 mV) when they
are held in the air and the Canin
+
instrument is connected to earth.
It is also a good idea to make comparison measurements on areas that are clearly damaged against
areas that are clearly intact. (e.g. at the base of a column with obvious corrosion compared with
columns at a height of approximately 1.50 m without any visual damage.) Here also stable values
should be obtained, whereby the measured values in the damaged area should be significantly more
negative than the values from the undamaged area.
