Properties of fresh and hardened high strength steel fibers reinforced self-compacted concrete

Abstract

Properties of fresh and hardened high strength steel fibrous self-compacted concrete were studied in this investigation. One reference high strength self-compacted concrete mixture is used, with five percent (by weight of cement) silica fume and eight percent of the cement replaced by limestone powder. Three steel fibers percentages by volume of concrete are used (0.4, 0.8, and 1.2). The used steel fibers were a shelled Harex type with irregular cross-section, equivalent diameter of 0.93 mm, and 32 mm long. Super plasticizer was used to improve the workability and flow ability of the mixes. The test results showed that the presence of steel fibers decrease the flow ability, and increase the time of spreading, segregation, and passing ability of the fresh concrete. For the three fibers percentages used, the properties of fresh concrete were within the recommended specifications for the self-compacted concrete. The test results showed that the self-compacted concrete exhibited an early strength development rate more than that for plain normal concrete due to the presence of the fine materials. As for normal concrete, the test results showed also that the increase in the splitting strength is more than the increase in the compressive strength due to the presence of the steel fibers and this attributed to the different failure mechnism of the two tests. The brittle mode of failure of the high strength unreinforced specimens changed to a ductile one due to the presence of the steel fibres.