MMP20 SONO-DIS (option D)
Page 34
Hauser
The exact positive or negative G-Set value which has to be factored in for the rock type
(location) and entered into SONO-DIS can be checked or determined in two ways:
A) By comparing the SONO-WZ measurements with several correct values for the target water
content of the concrete.
With concrete mixes that are blended with dry aggregates.
B) By comparing the SONO-WZ measurements with several correct kiln-dried values or by
determining the water content after kiln-drying.
The kiln-dry water content is calculated as follows:
Kiln-dried value = effective water + core water + additives that behave like water.
SONO-WZ also measures additives that behave like water during the measurement process. This
must also be taken into consideration when evaluating and determining the w/c water content.
Applicable value for the core water for the calculation when kiln-drying:
If a very absorbent lime grit absorbs 2% water, for example, this would be 34 liters of core water
with one cubic meter aggregate fraction, presuming a bulk density of the aggregates of 1700kg/m
3
.
Core water = moisture * raw density of rock /100 = 2% × 1700 / 100 = 34 liters per cubic meter
Water absorption (WA
24
)
Applicable value for the G-Set in SONO-DIS:
As the SONO-WZ cannot measure 100% of the core water, in this example a G-Set value of
approx. -23 liter/m
3
could be suitable (= 2/3 of total core water of 34 liters) if the effective water
content or effective water is to be measured with SONO-WZ.
The G-Set value calculated or assumed once for the rock type or location should be determined or
checked by performing comparison measurements either with reliable mixes with dry aggregates or
with several reliable kiln-dried values.
Kiln-drying as a reference value
The configurable
G-Set
parameter in SONO-DIS can be used to adapt the calibration of SONO-WZ
to the concrete formulation with the rock type by performing kiln-dried comparison measurements.
Please note that it is not easy to kiln-dry fresh concrete correctly. Fresh concrete must be kiln-dried
relatively quickly to prevent the cement from gradually setting during the kiln-drying process. If the
kiln-drying process is too slow there is the danger of the free water in the fresh concrete binding in
the cement. This would falsify the measurement result when the sample is weighed because the
water in the kiln would be chemically or crystalline bound and the calculated kiln-dry water content
would be too low as a result.
