A simple gravimetric method for determining the moisture diffusivity of building materials

A simple gravimetric method for determination of moisture diffusivity which is able to give a moisture diffusivity vs. moisture relation point-wise is presented in this paper. The method can be employed in determining moisture diffusivity of anisotropic materials also in the case if one spatial dimension of the specimen is significantly smaller than the other two, which is the case of the most of lining materials, for instance. Practical application of the method is demonstrated for two fiber containing plate building materials produced in the Czech Republic, Dekalux and Dekalit P. Experimental results show that while for lighter Dekalit P, an order of magnitude difference in the moisture diffusivities κ for the two basic orientations, i.e. along and through the plate, is observed, for the heavier Dekalux the differences in κ are within the error bar of the experimental method. The method is tested by its application to rod samples, and a comparison with two commonly used methods is done with both mentioned lining materials and also with an extruded porcelain mixture which can be considered as a well homogeneous material. The results of this comparison show a reasonable agreement, taking into account the approximate character of the method.