Equilibrium Moisture Content of High Strength Concrete Used in Hollow Core Slabs

The aim of this study was to measure equilibrium moisture content of hollow core slabs on both hygroscopic and capillary ranges. Because of the fabrication method of hollow core slabs, concrete grades and compacting methods used in the production differ from those used with reinforced concrete structures and elements. Test samples were taken from two slabs delivered by different manufacturers. Both slabs had similar geometry and were made of C50/60 grade concrete. Hygroscopic moisture equilibrium values were determined in climate chambers. Thin test specimens were used to perform tests within a reasonable time. Hygroscopic moisture equilibrium was measured at high relative humidities (RH), from 85 to 97 % RH. These measurements could be connected to the measurements of the retention curve done by a pressure plate. Measurements done in climate chambers and by pressure plate provided coherent results within the accuracies of these two methods. The results of two concrete slabs representing two different manufacturers differed significantly from each other, indicating the deviation of hygrothermal material properties even if the studied slabs were almost identical in many respects. Measured data is especially useful in modelling as well as analysing moisture damages.