Effect of mixture flowability on strength and fiber distribution of Ultra High-Performance Fiber Reinforced Concrete

Abstract

The uniformity of distribution and the orientation factor of steel fibers are crucial parameters that determine the strength and uniformity of properties of Ultra High-Performance Fiber Reinforced Concrete (UHPFRC). The paper considers the influence of flowability and the method of casting the concrete mixture on the strength and fracture energy in bending of UHPFRC. The flowability was determined by the spread diameter of the mixture from the Hägermann cone, which was 270, 300, and 350 mm. It was found that the compressive strength of UHPFRC increases from 142 to 155 MPa with an increase in the mixture spread diameter. The strength and fracture energy in bending of UHPFRC near the ends of the mold are on average 14.5 and 17.7% less than in the central part. A relationship has been established between the flexural strength of UHPFRC and the fracture energy as a function of the relative area of the fiber in the cross-section. The optimal flowability range of UHPFRC (270…290 mm) was established analytically and experimentally, in which there is no critical decrease in strength properties and the ability of the mixture to self-leveling is maintained. Negative effects were established when changing flowability, outside the specified range.