Limit of validity of the moisture diffusivity for the study of moisture transfer inside terracotta

• Published in: Materials and structures 2002, Vol.35 (245), p.42-49
• Main Authors: DIAW, M, PERRIN, B, MONLOUIS-RONNAIRE, J.-P
• Format: Article
• Language: English
• Subjects: Applied sciences; Buildings. Public works; Ceramic. Refractories. Terra cotta; Computation methods. Tables. Charts; Exact sciences and technology; Materials; Strength of materials (elasticity, plasticity, buckling, etc.); Structural analysis. Stresses
• ISSN: 1359-5997; 1871-6873
• DOI: 10.1617/13650

In order to establish the limits of the concept of water diffusivity, DW, an attempt was made to validate the Boltzmann's method used to identify it. It was shown that, for a medium strictly satisfying the equation of diffusion, the method gives quite good results, nevertheless with some inaccuracies for the extreme values of water contents. For studied material, a terracotta, identification becomes more difficult because of the dispersion of the wetting phenomenon observed for different specimens of the same material. It was shown that the mean behaviour of one sample is close to the probable behaviour of all the samples. Otherwise, the values of DW determined for wetting cannot be used to describe a drying process. Its practical interest is then considerably reduced. In order to test the influence of the gas phase pressure on the behaviour of the material, all the parameters necessary to describe, numerically, wetting and drying processes without resorting to DW were determined. An overpressure of the gas phase inside the material due to drying was seen. If the gas pressure effects are, numerically, switched off, no influence on water content profiles for this material was found. 10 refs.