Effect of bond conditions on local bond-slip relationships of ribbed bars in high performance self-compacting concrete

The bond of concrete to steel reinforcing bars is the basis for the concept of reinforced concrete as a construction material. One of important bond-related issues is the bond strength-bar slip relation, which has an influence on the failure mode and rotation of structural joints. This relation can be predicted by bond-slip models and it depends on the bond behaviour at the reinforcement-concrete interface. However, the currently-known bond-slip models offer limited applications to well-studied normal concretes only. This article proposes local bond-slip relationships for high performance self-compacting concrete (HPSCC) taking into account the quality of bond conditions. The studies were performed on specimens made of four different high performance self-compacting concrete mixes with varying contents of silica fume. Since the specimens had total heights of 480, 800 and 1600 mm, it was possible to measure the changes of the bond at individual levels. The results were next compared to those obtained for samples made of vibrationally-compacted high-performance concrete (HPC). It was demonstrated that the bond-slip model for normal concretes seems to underestimate the bond stiffness and ultimate bond strength for the HPSCC and HPC mixtures. Moreover, it was proven that a change of the quality of bond conditions has an effect on the local bond-slip relationship. Finally, local bond-slip relationships were presented separately for HPSCC and HPC with respect to the quality of bond conditions. (C) 2019 Politechnika Wroclawska. Published by Elsevier B.V. All rights reserved.