Porositè des sols argileux en fonction de l'hydratation. lnfluence du type d'argile et des ciments sur leur stabilitè structurale

By mercury and nitrogen porosimetry measurements on soil samples equilibrated at different water potential, the role of the type of clay minerals and cements on microstructure modifica¬tions has been evidenced. On a smectite soil (Vertisol) the changes of microstructure resulted mainly with respect to swelling behaviour of morphological units. In contrast, in Mediterranean Terra Rossa, the iron cements play the main role by hindering the dispersion of illitic microdomains, forming a rather rigid framework. In a Regosol lacking cements and containing, as dominant clay mineral, kaolinite which is characteri¬zed by low surface activity, the most typical feature seems to be a marked tendency to disperse with the increase of water content.