Abstract
Remaining moisture in concrete with some drying time begins to change its distribution after the drying surface is sealed up. This paper describes an investigation into such a moisture redistribution in order to discuss the effect of moisture in concrete on the failures of the finishing layers applied directly on concrete substrate. In the experiment both pore humidity and moisture content in concrete standing for a slab on deck plate were measured before and after the drying surface was sealed with a vapor-tight surface layer. After being sealed the pore humidity in concrete began to change its distribution, and finally the portion under the surface layer became highly humid in spite of a long period of drying. This moisture redistribution may cause the failures of the finishing layers. From the measurement of the moisture content, however, such a moisture redistribution could hardly be recognized. The difference between the redistributions of pore humidity and moisture content is due to the hysteresis of the sorption isotherm of concrete. A numerical estimation of the moisture behavior in concrete with consideration of the hysteresis was also presented. The estimation presented was proved to be very useful for the discussion of the moisture load against the finishing layers.
