Shear behavior of ultra-high-strength steel fiber-reinforced self-compacting concrete beams

Ultra-high-strength concrete (UHSC) is characterized with its high compressive strength, yet it shows very brittle failure compared to normal-strength concrete due to a limited post-crack behavior. The inclusion of steel fibers would enhance the post-crack response of this high class of concrete. Since UHSC is produced with very low water to cementitious materials ratio, the inclusion of steel fibers would reduce the concrete workability. The development of self-compacting concrete (SCC) opened the avenue for resolving the workability issue. In this study, the shear response of ultra-high-strength fiber-reinforced self-compacting concrete beams (UHS-FR-SCC) has been investigated. The impact of varying the steel fiber volume; V-f = 0.4%, 0.8% and 1.2%, on the shear response has been investigated. The shear response of the UHS-FR-SCC beams has been compared with that of similar beams made of normal strength concrete (NSC). The addition of steel fibers significantly increased the shear capacity of the concrete beams. The shear strength gain increased with an increase in the amount of steel fibers. The use of steel fibers had a more pronounced effect on the incremental shear strength gain of the NSC beams than the UHSC beams. Test results indicated that the inclusion of steel fibers with proper volume fraction can be used as a substitution of the internal steel stirrups. The obtained results could be used as input data to examine the validity of current models for shear strength prediction of UHS-FR-SCC beams.