Hygroscopic moisture in concrete

The work has been concentrated on developing a method of calculating the drying of moisture in hydrating concrete. A great number of theories have been available but could not be used because the necessary material properties regarding moisture were missing. By extensive laboratory investigations the most essential material properties in respect to moisture have been determined.--The sorption isotherms for concrete of different composition and age have been evaluated as well as the progress of hydration of some cements. Flow measurements and several drying experiments have given the effect on the diffusivity of different factors in the composition. Especially the water-cement ratio and the air content have been found most important.--Using these material properties a computerized calculation model has been developed for the drying of concrete. At a comparison to a number of control experiments in a full scale a good correspondence has been found.--Hygrometric methods of moisture measurements are shown to have several advantages. The state of moisture is expressed in a far better way, small samples can be used and the accuracy is much better than when measuring the moisture content. (author abstract)