Abstract: Based on Bingham model, the rheological properties of fresh concrete with varied coarse aggregate gradation of three sizes were tested using an ICAR rheometer.The effects of coarse aggregate gradation on slump flow, yield stress and plastic viscosity of concrete were investigated and then the coarse aggregate gradation were optimized.Results indicate that the gradation of coarse aggregate has significant effects on flowability and rheological parameters of fresh concrete.On the other hand, the optimum composition of three sizes aggregate could be determined by controlling the rheological parameters of concrete.Therefore, it is a better way to optimize the concrete mixture design by limiting the range of rheological parameters.

Key words: optimization of gradation;contours;rheological behavior;concrete