Determination of readiness for laying based on material moisture, corresponding relative humidity, and water release

Abstract

The moisture content of the subfloor has to be determined before installation to avoid damage to the floor covering. Only if readiness for layering is reached, can an installation without damage be expected in all cases. In general, three approaches exist to measure residual water content: determination of moisture content, determination of water release, or determination of the corresponding relative humidity. All three approaches are tested under laboratory conditions at eight screed types including two samples thicknesses in each case. Moisture content and water release are measured by sample weighing, the corresponding relative humidity is measured by embedded sensors. All three approaches are compared and correlated. The evaluations show only a weak correlation and, in several cases, contradicting results. Samples are considered ready for layering and not ready for layering at the same time, depending on the chosen approach. Due to these contradicting results, a general threshold for a risk of damage cannot be derived based on these measurements. Furthermore, the experiment demonstrates that the measurement of corresponding relative humidity is independent of the screed type or screed composition considered. This makes humidity measurement a potentially very promising approach for the installation of material moisture monitoring systems.

A single‐sided 1H NMR study of the self‐drying properties of a ternary self‐levelling underlayment

“…Furthermore, with respect to the RH after 15 minutes, the limit of 75 % RH is also reached after around 12 hours. These results do not correspond well to past results on screeds [5], where a water transport of only about 1.25 g/m²/h was found that corresponded with a relative humidity of 85 % and thus, laying readiness. The results shown here indicate that the measurements of water release provide interesting information on the drying behaviour of a material.…”

“…For the CRH method, chemically bound water does not contribute to the result, as no water vapour pressure is exerted. Last, to fully evaluate the laying readiness, the water release from the surface might be considered [5]. For regular cementitious screeds, a release of up to 30 g/m²/d (1.25 g/m 2 /h) was found to coincide with a relative humidity within the material of 85 % that marks the limit between unbound water in capillaries and the cement gel structure [5].…”

About the Dominance of Mesopores in Physisorption in Amorphous Materials

“…295 K). On the following morning, the samples were stored in a ventilated climate chamber at an ambient relative humidity of % RH and an ambient temperature of K. Further details are discussed in [ 31 , 67 ].…”