Modelling the moisture redistribution in concrete floors with screed and flooring material with varying properties

Flooring materials and adhesives can be degraded by high pH moisture from e.g. concrete. One way to avoid this degradation, is to dry the concrete and the screed to a sufficient moisture state prior to application of the flooring material. One way to evaluate the moisture state in the materials sensitive to high pH moisture is to calculate the redistribution of moisture in the flooring system from application and onwards. The calculations require substantial knowledge in both moisture related material properties and mass transport calculations in porous materials. The availability of more user-friendly calculations tools stresses the need for a common methodology for both performance and documentation of the calculations. Several input parameters are needed for the calculation, such as boundary conditions, initial moisture distribution and material properties. The most important material properties are the water vapor sorption isotherms (desorption, absorption and scanning) and moisture transport coefficients. This study is investigating the sensitivity of the moisture redistribution calculations to different input parameters, and assumptions needed for the calculation. It is also clarifying what relative humidity intervals that are relevant for different materials in the system and identifying a required accuracy in the different material properties. A first part of round-robin studies with selected cases has been performed to evaluate difference between calculations tools and users