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In general, fibre reinforced concrete (FRC) contains a single type of fibre. The utilize of several
fibre types in FRC in an appropriate combination and proportion can improve both the properties of
concrete and the synergy of their performance. Such a fibres mixture is usually called as hybrid fibres.
Good interaction between various types of fibres can surpass the action of single fibre in FRC. The fibres
should be selected so as to counteract the development of cracks and ensure continuity of stress transfer
in the full strain range. The first type of fibres should be shorter to bridge microcracks and control
their growth. The remaining fibres types should have increased length and strength to smoothly arrest
the propagation of macrocracks. In recent years, a lot of investigations have been carried out to assess
the flexure-shear strength of concrete beams containing mainly steel fibres. On the other hand, there is
little research on the flexure-shear strength of hybrid fibre-reinforced high-performance concrete (HPC)
beams. The addition of fibres to the HPC is particularly attractive as its brittleness may be limited.
Despite the increase in the HPC cost, the application of hybrid fibres can be justified to provide a
structural alternative to the stirrups in reinforced concrete beams. This study is aimed at investigating
the possibility of replacing conventional shear reinforcement with hybrid fibre reinforcement in high
performance concrete under flexural loading. Therefore, nineteen HPC beam specimens reinforced with
tensile longitudinal steel deformed rebars were constructed and tested. Glass fibres, polypropylene fibres
and steel fibres were used as reinforcing discrete hybrid fibres of varying fibre volume fractions 0%,
0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25% and 2.5%, as well as with two different proportions
1:1:1 and 0.25:1.25:1.5. An investigation was performed on the influence of the addition of hybrid
fibres on the cracking response, load-carrying capacity, and ductility of the HPC beams. The addition
of fibres increased the first-cracking load, ultimate shear strength, ductility, and mitigated the crack
width of the steel rebars-reinforced HPC beams. The results of this study show that it is possible to
replace stirrups with hybrid fibres.
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