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, p erformed with a plane-to-plane rheometer, it appears that the relation ship between torque and rotation speed is not exactly linear. The fres h 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, resp ectively. tau'(o), a and b are three material parameters describing th e concrete behavior. Among other advantages, this new description avoi ds the problem negative yield stress encountered with the Bingham mode l.