This paper reports the results of an experimental investigation on the behaviour of High Strength Concrete (HSC) reinforced with different types of steel fibre (copper-coated micro steel fibres, deformed macro steel fibre and hybrid steel fibre). A total of 40 cylindrical specimens with 100 mm diameter and 200 mm height were cast and tested for compressive and split tensile strengths. Three groups of steel fibre reinforced HSC specimens were prepared. The first group included 2, 3, and 4% by volume of coppercoated micro (CM) steel fibre; the second group included 1, 2 and 3% by volume of deformed macro (DM) steel fibre; and the third group included 1.5% (1% CM + 0.5% DM), 2.5% (1.5% CM + 1% DM), and 3.5% (2% CM + 1.5% DM) by volume of hybrid (H) steel fibre. Plain HSC specimens without steel fibre were also prepared. The experimental results showed higher improvements in the compressive and split tensile strengths of the HSC with the inclusion of 3, 2, and 2.5% by volume of CM, DM and H steel fibres, respectively, compared to the plain HSC.

High strength concrete has higher strength but lower ductility. Inclusion of single type of fibers into concrete has been proven to improve the behavior of concrete to a limited extent. However, recently it was found that the behavior of concrete can be improved more with the addition of hybrid fiber i.e., a combination of different types of fiber. This paper presents the results of an experimental investigation on the behavior of Hybrid Steel Fibre Reinforced High Strength Concrete (HSFR-HSC). A total of eight cylinder specimens with 150 mm in diameter and 300 mm in height were cast and tested under uniaxial compression. Three different combinations of HSFR-HSC specimens and reference specimens without steel fibers were prepared. The first combination of HSFR-HSC included 1.5% Micro Steel (MS) fibers and 1% Deformed Steel (DS) fibers. The second combination included 1.5% MS fibers and 1.5% Hooked-end Steel (HS) fibers. The third combination included 1% DS fibers and 1.5% HS fibers. The experimental results showed that the addition of hybrid steel fibers improved the strength and ductility of high strength concrete compared to the reference specimens. The results also showed that the specimens reinforced with different hybrid steel fibers failed in a ductile manner, while the reference specimens failed in a brittle manner.

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The strength and ductility of high strength concrete columns improve with the addition of steel fiber. This paper reports the behavior of circular High Strength Concrete (HSC) columns reinforced with Hybrid Steel Fibers (HSF) under different loading conditions. In this study, HSF consisted of a combination of macro steel fibers and micro steel fibers. A total of eight circular specimens of 205 mm diameter and 800 mm height were cast and tested. All specimens were reinforced with same amount of steel reinforcements. The specimens were divided into two groups of four specimens. Group RC (reference group) contained no steel fibers. Group HSF (hybrid steel fibers) contained 2.5% by volume of HSF. From each group one specimen was tested under concentric loading, one under 25 mm eccentric loading, one under 50 mm eccentric loading, and one under four-point loading. The results showed that the specimens reinforced with HSF achieved higher strength and ductility compared to RC specimens under different loading conditions. It was also observed that the presence of HSF delayed the spalling of the concrete cover.