MMP20 SONO-DIS (option D)
Hauser
Page 25
Measurement procedure for concretes with flow class F5, F6
Very liquid concretes tend to segregate, and are also not easy
to measure. There is the risk of larger parts accumulating on
the base of the bucket. Furthermore, there is also the danger
that fine particles can gather around the surface of the
SONO-WZ probe once the probe is inserted, with the result
that the values measured for the water content would be too
high. Therefore we recommend the following procedure for
concretes with a flow class of F5 to F6:
1)
Only fill ¾ of the 12 liter bucket with concrete.
2)
Fully insert the probe head with the
covered (plastic) W/C
shovel
vertically into the concrete at the side of the bucket.
The shovel ensures that the larger gravel pieces do not "drift
away" from the probe head towards the side, which could
cause deviations in the measurement.
3)
Slowly push the tip of the probe - with the black ceramic
surface at the front - in a diagonal direction towards the
opposite side of the bottom of the bucket so that the handle
rests on the edge of the bucket (see the red arrows). This
ensures a representative concrete mix is present around the
surface of the probe.
Repeat this procedure a number of times, inserting the
probe at a different point each time. Delete any individual
measurements that are too far from the displayed average
value.
Note:
Kiln-dried sampling and kiln-dry testing of concretes
with a flow class of F5 and F6 can also deliver inaccurate
results. If the concrete for the kiln drying process is taken
from the surface of the bucket or the base of the bucket, there
can be a difference of up to 40 liters in the water content in
the case of concretes that tend to bleed!
After 4-5 measurements:
If the standard deviation after 4-5 measurements is not acceptable (i.e. >0.5) or if
the measured values fluctuate too much, additional individual measurements must
be taken. Here we recommend mixing the fresh concrete in the bucket again.
Ideally, use professional mixing tools, such as the stirrer illustrated below, as this
ensures that any fresh concrete which may have segregated slightly as a result of
the measurements is blended again in a uniform and optimum manner.
However, take care not to mix the concrete for too long as water can escape from
the concrete. Afterwards, additional measurements can be taken as explained in
Point 3.
