Bond performance of ribbed steel reinforcing bars in vibrated and self-compacting concrete

Abstract

The bond between steel reinforcing bars and concrete plays a vital role in the effective performance of reinforced concrete as a composite member. Failure of this bond can lead to catastrophic structural failure of buildings and infrastructure. Factors influencing the steel–concrete bond include concrete strength, bar properties such as embedment length, ribs and diameter, and confinement in concrete. This paper reports on an experimental study to evaluate the bond performance of ribbed reinforcing bars in self-compacting concrete and to compare it with that in normal vibrated concrete. Different characteristic concrete strengths (20, 40 and 60 MPa), bar diameters (12 mm and 16 mm) and embedment lengths (2·5 and 5 times bar diameter and full depth of specimen) were used. The bond strength measurements were based on direct pull-out tests in accordance with IS 2770-1 and a comparison was made with the test procedure specified by Rilem TC 9-RC. The experimental bond stress values obtained were compared with those obtained from various models available in the literature. An analytical model was then proposed to predict the bond strength of ribbed reinforcing bars in both vibrated and self-compacting concretes.