Министерство высшего и среднего специального образования республики узбекистан ўзбекистон республикаси

Samples and measurement results 
For the tests, with the light-optical moisture sensors following screed and mortar samples were 
used: 
1) calcium sulfate floor screed CAF-C25-F5 Maxit with 1.92 g / cm³ (dry) 
2) cement mortar CEM I 42.5 R with w / c = 0.4 and 0.7; Natural sand with s / z = 3/1 
The dry sand according to DIN standard EN196-1 has a grain size of about 0.15 to 1.5 mm (d50 
= 0.7 mm). About a specially adapted for these investigations multimeter DT830 the readings were 
read regularly manually. The power supply for the light emitting diode has been realized in the 
multimeter as an integrated component. All sensors tensions were measured sequentially. For the 
recording of measured values are about 5 sec. needed. The lab was air conditioned with a constant 
temperature of 21 
o
C and a relative moisture of about 55%.In Figure 2 the complete measurement 
setup can be seen for a screed-examination. Here it was important to measure the moisture content at 
different levels of a calcium sulfate screed. Two light-optical sensors have been installed. An L1 
sensor was in the upper part (h = 4.5 cm), and a second L2 sensor in the lower region of the screed (h 
= 0.5 cm) was applied. The total height of the screed was h = 5.0 
cm. During the measurement by means of light-optical moisture 
sensors, the ambient temperature and moisture were measured at 
the same time. The moisture sensors are shown covered with 
calcium sulfate screed. Understandably, only the upper part of 
Fixbasket for the sensors and the electrical lines are seen. For the 
studies were conducted in two different cement mortar (w / c = 
0.5; 0.7), the same preparations performed with the metal basket, 
as the CaSO4 screed, but with only one sensor each mortar 
sample. The total height of the mortar was 8.0 cm. Each sensor 
was located at a height of h = 4.0 cm. The mortar and screed 
samples were checked gravimetrically during setting and 
hardening. For all samples, the external water delivery was made 
only on one side on the surface of the material layers. 
In Figure 3, the photo-diode voltage can be seen as a function of time for the setting and 
hardening of CaSO
4
screed. The diagrams show a different curve during hardening. Using the 
calibration curve then the moisture penetration of the screed was determined. Both measurement 
curves fall after a sensor-related balance-setting time (a few hours) due to the water consumption by 
the setting reaction (s. Gl.2) from. 
CaSO
4
+ 2H
2
O → CaSO
4
∙ 2H
2
O
(2) 
The investigations show that the light-optical moisture sensors the moisture content can 
significantly differentiate into different depths. This is a noticeable advantage of the LOF sensors over 
other measuring methods, such as the 
electric or ultrasonic measurements. The 
sensors can be applied in the screed 
targeted at the measuring location. Thus, 
it was demonstrated that in different 
depths of the screed, as expected, the 
moisture content differences in the 
timing takes (water transport in the 
screed). One can clearly see how the 
surface of the sample, the water 
evaporates faster than the water content 
in deeper areasdecreases. Both occupy 
independent measuring methods that 
CaSO
4
- screed sample "by dried" after 
about 15 days. 
Fig. 3: Photo diode voltage as a function of time in CaSO
4
 screed 
In studies in the cement mortar, the influence of w / c was - value placed on the timing of the 
local moisture content at the center of considerations. In Fig. 4 the change in the normalized 
photodiode voltage during the setting and hardening of the fresh mortar samples with different w / c 
 
Fig. 2: fix the sensors in metal 
basket at different depths 

---

189 
ratios is shown. The sensors are located approximately at an average height of 8 cm high cement 
mortar layer. The studies show that 
in the setting and hardening phase 
LOF sensors after about 10 hours at 
w / c = 0.4 and approximately 40 h 
at w / c = 0.7, a drastic drop in the 
measurement signal and for the local 
moisture content (free mobile water) 
identification.
Fig. 4: Temporal change of the 
normalized 
photodiode 
voltage 
during the setting and hardening of 
cement mortar samples 
This use of water is related to the setting reaction (CSH-phase binding). Fig. 5 now provides the 
relative voltage waveforms in the cement mortar samples after 28 days again saturated with water 
during the drying of the solidified microstructure. The decrease in the local moisture content (in the 
middle sample height) must be held 
immediately after the start of 
measurement. After less than 12 
hours, about half of the mobile water 
is already escaped into the rigid, 
solidified pores rock in follow fast 
capillary transport of the samples. 
Due to the larger pore volume and 
thus higher water content in the 
structure, the relative decrease of the 
local water content in theexponential 
curve is slightly slower than in the 
sample with w / c = 0.4 in the 
sample with the w / c ratio of 0.70. 
Fig. 5: Normalized photodiode voltage of cement mortar sample after renewed water saturation