A NEW RHEOMETER FOR SOFT-TO-FLUID FRESH CONCRETE

This article describes the development of apparatus designed to charac terize the rheological behavior of fresh concrete both in the lab and on site, in the range of consistency from soft to fluid. The principle s that governed the design of the rheometer ave first recalled. It is a torsional rheometer, in which a sample shaped like a hollow cylinder is sheared between two horizontal planes. The conduct of the tests is then described, followed by their processing, which yields, in partic ular; two physical quantities to characterize a concrete, the shear yi eld stress (tau(O), in Pa) and the plastic viscosity (mu in Pa.s). The se parameters may be measured with or without vibration, giving differ ent values in each case. Later; the results of experiments are describ ed. They deal with the detection, with only one sample, of the phe nom enon of loss of workability, and with the pumpability of the concrete on site, respectively. The article concludes with a look at the prospe cts for industrial use of the BT RHEOM rheometer.