Surface energies of hardenned cement paste depending on relative humidity

Abstract

In the lower region of relative humidity, one assumption of the Munich Model regarding the volumetric changes in hardened cement paste (hep) is that adsorbed water molecules decrease surface energy. Recent work with inverse gas chromatography (IGC) on hep provides the first experimental evidence to support this assumption. Under conditions of varying relative humidity, the equipment used (iGC SMS— POROTEC) allowed a series of pulse experiments with non-polar (alkenes) and polar probe molecules at temperatures in the region of 30°C. From the retention times, specific interaction energies and a dispersive surface energy of the solid can be derived. The results are in agreement with the findings of many other experiments conducted under different relative humidities. Furthermore they may help to understand strongly nonliner moisture related phenomena like shrinkage, swelling, change in the pore size, strength, and diffusion in hardened cement paste.