Characterization and optimization of hardened properties of self-consolidating concrete incorporating recycled steel, industrial steel, polypropylene and hybrid fibers

Abstract

Abstract This paper presents an experimental/analytical investigation to examine the feasibility of hybrid fibers in self-consolidating concrete containing different fiber types (industrial steel fiber, recycled steel fibers, and Polypropylene fiber), contents (0.5%, 0.75%, 1%, 1.5% in Vol.), and combinations (as single and blended fibers). Fresh and hardened properties of the fiber reinforced self-consolidating concrete were assessed, considering total fiber volume fraction of 1.5%. The fresh state properties were assessed in terms of flow slump diameter and T500. Moreover, the hardened state properties of specimens were characterized by using the ultrasonic pulse velocity, the compressive strength, the splitting tensile strength, the flexural strength, and the impact resistance. Then, a statistical method based two-parameter Weibull and an optimization procedure were executed on the collected experimental results. The results showed an enhancement of mechanical properties and impact resistance in self-consolidating concrete by the addition of fiber, which was significantly governed by fiber type, content, and combination. Moreover, the optimization procedure revealed that the best performance in terms of maximum mechanical properties and impact resistance, as well as the minimum cost, was achieved in the mixture reinforced with 1.5% recycled steel fiber (Rst1.5) as mono-fiber and the mixture reinforced with 1% industrial steel fiber and 0.5% recycled steel fiber (St1Rst0.5) as hybrid fiber. In addition, the statistical study showed that the two-parameter Weibull could be adopted to analyze the distribution of the first crack (FC) and ultimate crack (UC) impact resistance.