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5 Correct Handling in fresh concrete
SONO-WZ works with state-of-the-art TRIME TDR-method (Time-Domain-Reflectometry) based on radar
technology. Plastic and liquid concretes with slump values >30mm can be easily measured with SONO-WZ. An
automatic averaging with 4 to 5 single measurements ensures a procedure with representative material mix on
the probes surface. Following the structured working method with SONO-WZ, precise and reliable results are
displayed within few minutes.
By using and detecting the electrical attenuation of the radar pulse it is possible to determine the cement content
and allows therefore higher security for testing of a concrete type which must be controlled continually.
Note:
Concretes which do not conform to standards (e.g. tend to bleed), may lead to considerable fluctuations of
the measuring values.
5.1 Measurement field of the SONO-WZ probe
The effective penetration depth of the SONO-WZ probe electrical
measuring field is about 50mm around the probe surface.
It is to consider that with all dielectric measurement methods like TDR,
microwave or capacitive, the electrical field distribution is not linear but
exponentially. This means that the intensity of the electromagnetic field
is the highest at the probes surface and decreases with more distance.
In consequence this means that bigger gravels which lies tightly at the
probes surface can influence the measurement field significantly.
To achieve a best possible result it is advisable to make several single
measurements at different places inside the fresh concrete. With smaller
grain sizes up to 4 single measurements, with bigger grain sizes more than
4 single measurements are necessary. The higher the number of single
measurement cycles, the higher the average measurement accuracy1
Attention
Around the probe head of SONO-WZ there should be no metal parts during the measurement procedure,
because metal can influence the electrical field. Best and easiest way is to use a plastic bucket filled with fresh
concrete. To avoid air gaps the concrete should be compressed by several stamps of the bucket on the ground.
The probes surface must be clean and free of concrete crusts and if necessary the probes surface must be
cleaned with a wire brush.
The probe head of the SONO-WZ must be completely immersed inside the fresh concrete during the
measurement.