New possibilities for measuring the humidity of concrete using cable humidity sensors

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Fig. 1: Diagram of the humidity sensors: 1 – sensor outer shell; 2 –polymer shell of the sensor; 3 – sealing; – porous shell; 4 – water molecules; 5 – electrical capacitance meter

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Fig. 2: Comparison of the areas of sensor technology capture of conventional humidity sensors and cable humidity sensors: 1 – standard point humidity sensor; 2 – cable humidity sensor

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Fig. 3: CHS generating the average humidity signal determined (along the cable length)

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Fig. 4: Difference of concrete moisture received from the CHS and conventional sensors : 1 – point sensor; 2 – volume sensor, scanned per concrete volume; 3 – cable humidity sensor; 4 – scanned concrete volume sensor

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Fig. 5: The humidity sensors of the cable must have been fixed to the reinforcement before concrete placement

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Fig. 6: Dynamics of the changes in the electrical capacitance and resistance of the three different structures of the CHS during concrete curing

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Fig. 7: Registration of the passage of the moisture front in a concrete element

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Fig. 8: Change of the CHS signal during curing of a concrete component and its subsequent wetting and drying

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Fig. 9: Multi-zone cable humidity sensor for concrete

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Fig. 10: Six-zone cable humidity sensor with indicator unit for critical excess of humidity in the control zones

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Fig. 11: Moisture measurement of concrete floor slabs in accordance with ASTM F2170 and using CHS

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Fig. 12: Leakage detection in concrete tanks with the aid of CHS

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Fig. 13: Monitoring of cold joints: 1 – cable humidity sensor;
2 – water stop

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Fig. 14: Demonstrating stand for monitoring the water moisture regime of concrete structures difficult to access a) in general; b) expansion joint; c) vertical expansion joint; d) „cold“ joint with water stop (3)

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Fig. 15: Possible areas of application ...

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Fig. 16: ... for cable humidity sensors in concrete

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Yuri Sakunenko
Honorary Inventor of Moscow, Ph.D., GEO Engimatic LLC, Skolkovo Fund, CTO HySens SIA

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A fundamentally new type of cable humidity sensors (also called CHS in this article) has been developed, patented and tested by Engimatic. This sensor allows the measurement of the average value of humidity inside concrete structures. It provides the possibility of online monitoring of moisture in building structures throughout the service life.

The practical significance of controlling the water content in concrete cannot be emphasized highly enough. It is sufficient to recall that it is the addition of water to the dry concrete mixture that gives rise to the actual hardening process of concrete. The kinetics of hydration and „maturing“ of concrete are directly related to changes in the moisture content. This allows the manufacturer to determine the optimum moment for stripping the formwork and to save 10 to 20% of the total costs of concreting at the same time, according to various estimates [1].

The two main natural causes for the...