Eignung zerstörungsfreier Messtechnik für die Bestimmung der Belegreife von Estrichen

Abstract

Suitability of non-destructive measuring technology for the determination of the readiness for covering of screedsThe determination of the readiness for covering of screeds in the construction industry is usually carried out by using destructive methods, which require sampling and only provide punctual data. As non-destructive testing methods, various hand tools exist, which are based on electrical and capacitive methods and are easy to handle. In this study, a capacitive spherical probe, a 4-electrode probe in Wenner configuration and microwave probes were tested. With the exception of the 4-electrode probe, the hand instruments do not have sufficient sensitivity in ranges of low humidity < 1 M%, and therefore do not appear to be suitable for anhydrite-bound screeds with a readiness of covering at 0.5 M%. On the other hand, for cement-bound screeds, it is possible to record changes in the range of the readiness of covering. The readiness of covering is usually stated and determined in reference to the relative moisture content. For the purpose of really assessing the risk of damage, we suggest to rather use the "water loss" in g/m 2 /d. Our results show in direct comparisons that value of approximately 8-10 g/m 2 /d is a reliable indicator for the readiness for covering of all tested screed types.Bild 12 Darstellung des gravimetrisch bestimmten Feuchtegehalts über die berechnete Wasserabgabe von zementgebundenen Estrichproben ("CT")Depiction of the gravimetrically determined moisture content as a function of the water loss of cement-based screed samples ("CT")Bild 13 Darstellung des gravimetrisch bestimmten Feuchtegehalts über die berechnete Wasserabgabe von anhydritgebundenen Estrichproben ("CA") Depiction of the gravimetrically determined moisture content as a function of the water loss of anhydrit-based screed samples ("CA")