4. Basic information on Resitest-400M
From a long time ago, an inspection instrument which has the four point
electrodes had been used to measure and assess in soil strata. When the
Wenner
sensor
with
four
electrodes
was
used
to
measure
the
corrosion of the concrete, several problems had been found. To solve
these problems, papers have been released in the early of 1980's. The
Colebrand Ltd. in England has developed the Resistivity logger on the
basis of "measurement of the Electrical Resistivity of Reinforced Concrete
Structures for the assessment of Corrosion Risk by S.G. Millard, J.A. Harrison &
A. J. Edwards) The CNS Ltd. in England also has developed the Resistivity
meter on the basis of "Resistivity Measurements in Concrete" by A.J. Ewins,
and Proceq SA in Switzerland has developed the Resi as a new Resistivity
meter lately.
The Resitest-400M was designed to make accurate measurements with
easy operation by solving the problems and inconveniences of the
existing equipments.
Even though the measurement of corrosion of the concrete using the
Resitest-400M is very effective, there are a few difficulties that must be
overcome to obtain reliable results, owing to the character of the concrete.
Because the concrete is an electrically non-homogeneous material, it is
likely to be affected by the ambient temperature and the moisture
content of the concrete. Measuring the same point by the Resitest-400M, the
accuracy of the result should be within
±
1%.
However, it must be remembered that the resistivity of the concrete
can vary as the moisture content changes. Values of less than 1
㏀
.cm for
water-saturated concrete can increase to over 100
㏀
.cm for the same
concrete when oven-dried.
Resitest 400M-June-2011-mkc-6/28
