Magnetic resonance imaging studies of spontaneous capillary water imbibition in aerated gypsum

Kyung-Min Song (1) , Jonathan Mitchell (1) , Hamouda Jaffel (2) , Lynn F Gladden (1)

1 Department of Chemical Engineering and Biotechnology
2 SGR - Saint-Gobain Recherche

In this paper we investigate both capillary water imbibition and the sorptivity of aerated gypsum plaster, and how these sorption characteristics are related to the pore structure of the material. These characteristics are examined by monitoring mass change using the conventional gravimetric method and by obtaining water content profiles using nondestructive magnetic resonance imaging (MRI) techniques during capillary imbibition of water. Here, three different gypsum samples are investigated: one non-aerated reference gypsum sample and two aerated gypsum samples produced with different volumetric air fractions. The capillary water absorption into the reference sample follows t 1/2 kinetics (Fickian diffusion), where t is the time of ingress. However, in the aerated gypsum samples there are deviations from t 1/2 kinetics. The MRI results show unambiguously that two wetting fronts advance through the aerated structure ; an observation that cannot be made from the gravimetric data alone. The water content profiles of the aerated gypsum samples are therefore analysed by treating them as the sum of two separate absorption processes using Sharp Front (SF) analysis. The capillary water absorption properties of this material are well described as a parallel combination of fast absorption into fine matrix pores and slow absorption into a modified structure of matrix pores inter-connected to air voids introduced into the slurry by aeration. PACS 47.56.+r. flows through porous media PACS 47.55.nb. capillary and thermocapillary flows

Mots clés: Physical Sciences

Kyung-Min Song, Jonathan Mitchell, Hamouda Jaffel, Lynn F Gladden. Magnetic resonance imaging studies of spontaneous capillary water imbibition in aerated gypsum. Journal of Physics D: Applied Physics, 2011, 44 (11), pp.115403. ⟨10.1088/0022-3727/44/11/115403⟩. ⟨hal-00602612⟩