Casting position effects on bond performance of reinforcement bars

Abstract

The phenomena associated with the consolidation of fresh concrete (bleeding and plastic settlement) are commonly considered significant for the bond performance of reinforcement. However, rules to take care of such influence for design are not consistent amongst design recommendations and may lead to notable differences. With this respect, two failure modes generally govern the bond failure, namely the spalling of the concrete cover (also called splitting failure) and the pull‐out of the reinforcement. In this paper, a detailed investigation is presented on the influence of bleeding and plastic settlement on both failures modes, in an effort to understand their conceptual differences and to clarify how shall consistent design recommendations be formulated. Such investigation is based on a comprehensive experimental programme, comprising 137 pull‐out tests on specimens with different casting conditions, embedment lengths, loading arrangements and concrete covers. On the basis of the test results, the phenomenological differences between pull‐out and spalling failures are clarified, as well as the main influencing phenomena (particularly the potential presence of cracks and voids under the reinforcement and the mechanical properties of concrete). On this basis, a physically‐consistent approach is presented to consider the casting conditions on the bond performance and failure modes.

X-ray CT Investigation of Bond Mechanism in Reinforced SCC Elements of Different Placement Technology

“…The bond in a reinforced concrete element is induced by several mechanisms in the vicinity of the concrete–steel interface. This was presented in detail in the literature [ 3 , 17 , 18 , 19 , 20 , 21 ].…”

Influence of casting position on cracking behavior of reinforced concrete elements and evaluation of latest proposal for EN‐1992 and MC2020: Experimental study

“…The reason for this effect is the migration of water to the top of the element (bleeding) and consolidation of concrete at the bottom of the element as the heavier constituents of the concrete mix will tend to displace the lighter ones. Because of this, concrete compacity and strength are larger at the bottom of the section 3–5 . This process also leads to uneven settlement of the concrete, because the settlement is hindered by the steel bars located at the top of the section, which do not move since they are fixed to the formwork.…”

“…Because of this, concrete compacity and strength are larger at the bottom of the section. [3][4][5] This process also leads to uneven settlement of the concrete, because the settlement is hindered by the steel bars located at the top of the section, which do not move since they are fixed to the formwork. The result is that voids are created under the bars and longitudinal cracking occurs along the bar.…”

Bond behavior of plain round bar embedded in high ductile concrete under monotonic and cyclic loading

“…can ensure sufficient stress transfer and deformation compatibility, consequently avoiding localized failure of structures under earthquake action. 11,12 In order to have a basic understanding of bond performance between the deformed steel bar and HDC, a number of experimental studies have been carried out in the recent years. Deng 13,14 investigated the bond behavior of deformed steel bar embedded in HDC under monotonic and cyclic loading.…”

“…Combined action of steel bar and HDC was primarily dependent on the bond between these two materials, which had a great influence on the mechanical properties of reinforced HDC structures. Excellent bond behavior can ensure sufficient stress transfer and deformation compatibility, consequently avoiding localized failure of structures under earthquake action 11,12 . In order to have a basic understanding of bond performance between the deformed steel bar and HDC, a number of experimental studies have been carried out in the recent years.…”