Experimental and Analytical Investigation of Bond Behavior of Deformed Steel Bar and Ultra-High Performance Concrete

Abstract

Ultra-high performance concrete (UHPC) has been demonstrated to be a realistic alternative to less maintenance and significantly longer service life due to its better mechanical properties and low permeability. The bond performance of the deformed steel bar embedded in UHPC is critically important for the safety of the UHPC structures. This paper conducted an experimental investigation on the bond behavior of deformed steel bars and UHPC. The impacts of loading method, UHPC strength, steel fiber type and content, rebar diameter, and cover thickness were studied. The testing results revealed that the specimens failed in three modes: pull-out, splitting + pull-out, and cone failure. The main factors affecting the bond strength are UHPC compressive strength, cover thickness, and fiber characteristics. The peak slip of rebar-UHPC increases with cover thickness and rebar diameter. Finally, an analytical model of the bond stress-slip relationship between the UHPC and deformed steel bar is obtained, which is in suitable agreement with the test results.

Review of Bond-Slip Behavior between Rebar and UHPC: Analysis of the Proposed Models

“…The pin effect is particularly important in fiber-reinforced materials and can improve their mechanical properties. Since the effect is influenced by multiple factors, researchers typically consider it a variable when studying bond behavior, such as fiber type and size [11,18,19], fiber volume content [13,[17][18][19][20][21]27,33,34], and fiber orientation and distribution in the material [23,27,29]. However, in studies of bond behavior, most researchers only take the fiber volume content into account as a variable affecting the effect.…”

“…As shown in Figure 4b, Liang et al, studied the influence of 0 to 3% steel fiber volume content on the ultimate bond strength. When the steel fiber volume content increased from 1% to 3%, the bond strength increased by 23% [67]. Yoo et al, studied the influence of 1% to 4% steel fiber volume content on bond strength.…”

“…When the steel fiber volume content increased from 1% to 3%, the bond strength increased by 14%; when the steel fiber volume content increased from 3% to 4%, the bond strength value decreased to 68.28 MPa [48]. Some researchers concluded that the contribution of steel fibers to bond strength was not due to the difference in UHPFRC compressive strength caused by different steel fiber volume contents but depends on the number of fibers participating in the bridging at the crack [27,67]. With the increase in steel fiber volume content, steel fibers will exhibit aggregation, causing uneven distribution and reducing the effective fiber number [45,68].…”

“…Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) is a fiber-added ultra-high-performance material. Some researchers studied the variations in bond stress by changing the fiber type [18,19] and fiber content [20,21], and found that the fiber type did not have a significant impact on bond stress. The bond stress increased with the increase in fiber content, but the enhancement effect would be weakened at higher fiber content, and even negative effects may occur [20,21].…”

Numerical Simulation of Lap-Spliced Ultra-High-Performance Concrete Beam Based on Bond–Slip

“…The bond performance between steel bar and UHPC directly determines the mechanical performance of the reinforced concrete structure. Many scholars have studied the bond performance between steel bars and UHPC, mainly focusing on the direct pull-out anchorage test [23][24][25][26][27][28]. When the anchorage specimen is directly pulled out, the steel bar is in tension and the surrounding UHPC is under compression, which is inconsistent with the actual structural stress state.…”