RHEOLOGICAL TESTING AND MODELING OF FRESH HIGH-PERFORMANCE CONCRETE

The theological behaviour of fresh high performance concrete was inves tigated by use of a coaxial cylinder viscometer (BML Viscometer). Afte r a series of experiments it was observed that the equipment used was not very suitable for concrete mixes with slump values of less than ap proximately 10 cm. Also, for almost all mixes with a slump of less tha n 20 cm, plug flow occurred. By use of nonlinear regression analysis, however, a method for the determination of the two Bingham constants i s proposed, even when plug flow occurs. Using these Bingham constants, the predicted slump values obtained from a chart established by compu ter simulation showed good correlation with those observed experimenta lly. A model for the prediction of plastic viscosity based on Farris' theory is also proposed. With two adjustable parameters the model gave a good description of the various concrete mixes tested.