This study focused on a widely available UHPC product containing 2% steel fiber (by volume). One of the main goals of the research is to develop design recommendations for reinforcing bar embedded in UHPC, thus providing guidance for designers using reinforced UHPC in innovative applications. The epoxy coated bar had lower bond strength than uncoated bar the reduction was minimized when there is a sufficient embedment length that the bar yields before bond failure.Bars that yield before bond failure have less ultimate bond strength than high strength bars that do not yield before bond failure the reduction in bond strength is amplified as the ultimate bond strength increases.For bars with larger diameter, the bond strength decreases.Other UHPC mechanical properties, particularly those relevant to the post-cracking tensile behavior of UHPC, may be more appropriate for evaluating the bond strength of reinforcing bar in UHPC. The effect of UHPC properties on bond strength cannot be effectively represented by the compressive strength f’ c, or the square root of its compressive strength f’ c 1/2.An increase on the compressive strength of the UHPC results in an increased bond strength.Models that use bar spacing and bar cover to predict bond stress may need to be reevaluated in consideration of the added crack propagation resistance provided by fiber reinforcement in UHPC.The bond strength becomes a function of the mechanical properties of the UHPC. The adjacent bar will not help stop the propagation of the diagonal cracks. When the bar clear spacing is bigger than l stan(θ), the induced diagonal cracks from the pullout force will not intersect with the adjacent bar.Tight spacing between bars limits the ability of the fiber reinforcement to locally enhance the mechanical resistance of the UHPC. The decrease in bond stress for contact lap splice specimens is probably due to decreased contact area between the reinforcing bar and UHPC materials.L stan(θ), the bond strength decreases as compared to those having lesser spacing. Non-contact lap splice specimens, where the bar spacing is less than l stan(θ) †, exhibit higher bond strength than contact lap splice specimens when the bar clear spacing is bigger than.Bond strength increases as the side cover increases.The relationship between the bond strength and the bonded length for reinforcing bar embedded in UHPC is nearly linear, indicating that UHPC exhibits enhanced performance as compared to conventional high strength concrete.Increasing the embedment length of the bar increases bond strength.The following conclusions are based on the research presented in this report for deformed reinforcing steel embedded in UHPC. At the end, the proposed future research on this topic is included. Design details for using deformed reinforcing steel in UHPC are then recommended. The summary of the findings are presented in this chapter. The main factors affecting bond performance, including the structural characteristics like the embedment length, concrete side cover, bar spacing, bar size, and bar type, and materials properties such as UHPC compressive strength and bar yield strength are investigated. The specific UHPC material used in this study had a steel fiber content of two percent by volume and an average compressive strength of 13.5 ksi (93 MPa) at one day, 17.0 ksi (117 MPa) at three days, 19.4 ksi (133 MPa) at seven days, and 21.3 ksi (147 MPa) at 14 days. 5 and No.8 bars and ASTM A1035 Grade 120 No.4, No.5, and No.7 bars, were tested. Deformed reinforcing steel, including ASTM A615 Grade 60 uncoated No. The research discussed herein focused on assessing the bond strength of deformed reinforcing steel in UHPC. Bond Behavior of Reinforcing Steel in Ultra-High Performance Concrete
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