As is the case with composite materials, clay-based materials continue to play a very important role in various fields of modern industry, particularly in civil engineering, the cosmetics industry and the pharmaceutical industry. The development of these materials is most often declined through the mixture of a sifted clay powder and some often polymeric additives with distilled water thus allowing the formation of pasty solutions that evolve to a more or less orderly form; the speed or the control of this evolution remaining dependent on the physicochemical properties of these solutions or the conditions of their elaboration. Also and in a logic of quality control, the tests are often conducted at different levels to ensure that the operating conditions previously agreed are taken into account; these frequently relate to mechanical and / or thermal properties of the finished product or to properties related to the transport of these products in the fresh state in a confined environment. In this context and whatever the purpose sought, the characterization of the rheological behavior of aqueous solutions based on clay nowadays has a certain importance in terms of prediction and / or monitoring for the manufacture of these materials.

Our work is part of this approach and comes in two complementary parts; A purely experimental first part where we describe, using the rheostress I rotary rheometer (controlled by Rheowin software), the effects due to the formulation of aqueous solutions of a gray clay taken from the Moroccan atlas on their rheological behavior. And a purely theoretical second part where we propose a pressure drop-flow relationship when it is assumed that these aqueous solutions are transported in flexible pipes.

For the first part, we show in particular that the variation of the clay powder concentration makes it possible to identify several forms of rheofluidifying behavior with or without threshold. Particular interest is given to the case where the mass of the liquid phase is twice as large as that of the solid phase insofar as the rheological models listed on the rheowin software do not allow to approach the experimental readings with a good regression. The use of an error optimization method based on the calculation of standard deviations enabled us to verify for this particular case that the rheological behavior is very close to that observed by Robertson and Stiff in 1976 for the case of sludge drilling.

In the second part of this work, we propose, for the control of the transport of these solutions in flexible pipes, a set of approximate relations making it possible to connect the transported flow with the pressure drop imposed. In this context we insist on the particular case where the fluid is described by the Robertson Stiff model on the one hand and the transmural pressure is connected to the duct section by a constitutive equation similar to that proposed by Rumberger and Nerem in 1977 on the other hand. The method used is based on an asymptotic treatment of integrated conservation equations on a section in the case where the number of Womersley is assumed to be very small in front of the unit and where the terms of parietal friction are determined from a corrected form of the expression of Poiseuille.