Rheological Properties and Stability of Ultra‒High Performance Concrete Containing Coarse Aggregate

In order to improve the rheology and stability of ultra‒high performance concrete containing coarse aggregate (CA-UHPC), the effects of silica fume, coarse aggregate, and steel fiber contents on the rheological properties of CA-UHPC were investigated, and the relationship among the rheological parameters, fiber, and coarse aggregate distribution was established. The results show that CA-UHPC usually exhibits a shear-thinning behavior. The modified Bingham model has more accurate fitting results of rheological parameters, and the fluidity required for the rheological properties test can be controlled at 450‒690 mm. Increasing the silica fume content increases the yield stress, decreases the viscosity, and weakens the shear-thinning behavior. Increasing the coarse aggregate content firstly decreases and then increases the yield stress and viscosity, and intensifies the shear-thinning behavior. And increasing the steel fiber content increases the yield stress and viscosity, and intensifies the shear-thinning behavior. The number of steel fiber decreases from the top to the bottom of samples, while the proportion of coarse aggregate increases. The uniform dispersion degree of coarse aggregate increases with the increase of coarse aggregate content, but steel fibers deteriorate the uniform dispersion degree of coarse aggregate. The uniform distribution degree of steel fiber and coarse aggregate firstly increases and then decreases with the increase of steel fibers content.