The Effect of Fiber Geometry and Concentration on the Flow Properties of UHPC

The economic relevance of fiber-reinforced concrete has increased steadily throughout the years. Fiber reinforcement improves the mechanical properties of concrete structures, but at the same time has the disadvantage of worsening the workability of fresh concrete. In order to better understand the influence of the fibers on the fresh concrete properties, rheological measurements were carried out on suspensions with fibers of typical rod-shape and atypical ring-shape with volume fractions up to 3.3% and 4.8% respectively. The study is carried out on UHPC as a matrix fluid as well as on a silicone oil as a substitute fluid with comparable flow properties. Investigation on a substitute fluid has the advantage of excluding interferences caused by thixotropy and interaction with granular components.