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Operating manual – Material moisture measuring device T510
EN
Building moisture measurement
The electric conductivity of a dry, mineral construction material
(e.g. cementitious screed) is very low. When the
building material absorbs water, the conductivity of the material
can quickly increase or the resistance decrease.
What needs to be considered for the assessment of the measure-
ment results is that the results are affected by the material com-
position of the measured goods:
• The presence of soluble salts can distort the measurement
result substantially.
The more salt is present, the higher will be the displayed
measurement value.
• Yet another variable for the evaluation of the results is the
connection of the electrodes with the construction material.
In case of mineral, porous building materials, slight electrode
contact can cause a comparatively high contact resistance.
This can falsify the result of the measurement.
The accuracy of the measurement results is thus lower for min-
eral construction materials than for wood.
Building moisture measurements allow only qualitative conclu-
sions about the moisture (dry, damp, wet).
Quantitative conclusions about the moisture content of the min-
eral material to be measured can only be drawn by applying the
Darr procedure or the CM method.
Notes regarding the building moisture measurement
• Make sure you have set the correct type of measurement
(build).
• For measuring, the temperature of the building material
ought to be in the range of 20 °C.
• Observe disruptive influences due to electrically conducting
salts in the material:
Building-related moisture issues often occur in liaison with
water-soluble salts. Salts further the conductivity of con-
struction materials. During the measurement, the building
material has a lower resistance value. Which means that a
too high measured value is displayed.
• Observe disruptive influences due to electrically conducting
substances:
If a construction material contains electrically conducting
substances, it also has a lower resistance value, which then
simulates high moisture values. Which means that a too high
measured value is displayed.
From visual inspection it is usually not apparent, whether
there are any electrically conducting substances inside the
construction material. Some of the main error sources here
are in particular reinforcements, metal laminations and con-
ducting insulation such as slag in timber beam ceiling con-
structions. Especially in case of insulation materials with
metal lamination, measured values are often misinterpreted
during the resistance measurement.
Measured value assessment building moisture measure-
ment
For the measured value assessment of building material, the
measurement results of the resistance measuring method can
only be used as reference for a rough orientation.
Conclusions with respect to absolute humidity in mass % (M%)
can only be drawn for measurements, performed with the exact
same marginal conditions and compositions of the building mate-
rial as indicated for the test set-up in the chart below.
This graph was created in collaboration with the Institute of Build-
ing Materials Research of the RWTH Aachen (IBAC) and illustrates
the correlation between the measured value and the
mass-related moisture content of the examined building materi-
als. The presentation of the metrological results in this form now
permits a proper comparison of the measured value and the
actual moisture content. The list is limited to the most commonly
used mineral building materials. The measured values relate to a
reference temperature of 23 °C.
Plaster
The determination of the moisture content of plaster calls for sep-
arate examination. As can be seen from the following chart, the
volume-based moisture content of plaster changes little at air
humidity values between 0 and 0,8 (80-5). However, when
exceeding the level of 0,8 (80%), the moisture content skyrock-
ets.
Key
1
Moisture content (M%)
2
Measured value (digits)
3
C 30/37 concrete (conversion not possible)
4
Cementitious screed (conversion: CM% = M% -1.5 to 2)
5
Cementitious floating screed (conversion not possible)
6
Anhydrite floating screed (conversion: M% = CM%)
10
20
30
40
50
60
70
80
90
100
110
0
0
1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6