Abstract
This paper studied the influence of fiber volume fraction ( V f ), fiber orientation, and type of reinforcement bar (rebar) on the uniaxial tensile behavior of rebar-reinforced strain-hardening ultra-high performance concrete (UHPC). It was observed that the tensile strength increased with the increase in V f . When V f was kept constant at 1%, rebar-reinforced UHPC with fibers aligned with the load direction registered the highest strength and that with fibers oriented perpendicular to the load direction recorded the lowest strength. The strength of the composite with random fibers laid in between. Moreover, the strength, as well as the ductility, increased when the normal strength grade 60 rebars embedded in UHPC were replaced with high strength grade 100 rebars with all other conditions remaining unchanged. In addition, this paper discusses the potential of sudden failure of rebar-reinforced strain hardening UHPC and it is suggested that the composite attains a minimum strain of 1% at the peak stress to enable the members to have sufficient ductility.
Highlights
This research focuses on the uniaxial tensile behavior of rebar-reinforced ultra-high performance concrete
In comparison to reinforced concrete (RC) where the tensile load across the crack is only transferred by the rebar, reinforced ultra-high performance concrete (UHPC) allows the transfer of the tensile load across the crack by the combined effort of fiber-reinforcement and rebar
A total total of of sixteen sixteen different different series series based based on on volume volume fraction fraction and and orientation orientation of of fiber fiber and and type type of of rebar were tested under uniaxial tension
Summary
This research focuses on the uniaxial tensile behavior of rebar-reinforced ultra-high performance concrete (reinforced UHPC). In an un-cracked state, reinforced UHPC under tensile loading can be assumed to behave elastically with perfect bond (Figure 1a). This is similar to conventional reinforced concrete (RC) under uniaxial tension. In comparison to RC where the tensile load across the crack is only transferred by the rebar, reinforced UHPC allows the transfer of the tensile load across the crack by the combined effort of fiber-reinforcement and rebar This crack-bridging effect of the fibers increases the composite stiffness beyond the tension stiffening effect of rebar reinforced concrete [2]. It is worth noting here that this phenomenon of multiple cracking differentiates strain-hardening cementitious composites (e.g., UHPC containing at least 1.5 vol.% steel fibers of aspect ratio 65 [3]) in its composite tensile behavior from conventional fiber reinforced concrete (FRC)
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