Fresh concrete: A Herschel-Bulkley material

Some preliminary results of an experimental program on the rheological behavior of fresh 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 fresh concrete behavior is better described by the Herschel-Bulkley model: tau = tau'(n) + a (gamma) over dot (b); tau and (gamma) over dot are the shear stress and the strain gradient applied to the specimen, respectively. tau'(o), a and b are three material parameters describing the concrete behavior. Among other advantages, this new description avoids the problem negative yield stress encountered with the Bingham model.