A B S T R A C T R I~ S O M I~Some preliminary results of an experimental program on the rheological behavior of flesh concrete are presented. In the rheological tests, performed with a plane-to-plane rheometer, it appears that the relationship between torque and rotation speed is not exactly linear. The flesh concrete behavior is better described by the Herschel-Bulkley model: ~ = z' 0 + a ~b; ~ and ~ are the shear stress and the strain gradient applied to the specimen, respectively, z'0, a and b are three material parameters describing the concrete behavior. Among other advantages, this new description avoids the problem of negative yield stress encountered with the Bingham model. Quelques r&ultats pr(liminaires d'un programme exp(-

The ease of placement of concrete depends upon at least two physical properties, the yield stress and plastic viscosity. Currently the most common field test is the slump test, and it is related only to the yield stress. Therefore, a simple field test method intended to provide an evaluation of the two Bingham rheological parameters, yield stress and plastic viscosity, was developed. To determine the plastic viscosity the time necessary for the upper surface of the concrete in the standard slump cone to slump 100 mm was measured. The apparatus and test procedure are described. Semi-empirical models are proposed for the yield stress and for the plastic viscosity as function of the final slump and slumping time. The application of the modified slump test for the evaluation of the viscosity is limited to concretes with a slump of 120 to 260 mm. If the validity of this test is confirmed in the future, it could be used as a field quality control test.

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