Conclusions
To study the bond strength of reinforcing steel in RAC, 18 pull-out specimens as well as nine full-scale beam splice specimens were tested. Based on the results of this study, the following findings and conclusions are presented: Pull-out Specimens: The bond strength for the RAC-50 mix exceeded the CC mix by approximately 20%. The bond strength for the RAC-100 mix exceeded the CC mix by approximately 10%. All of the specimens had similar load-slip response. All of the specimens failed by an adhesion failure or local crushing between the reinforcing steel ribs and the base concrete. Beam Splice Specimens: The bond stress-slip behavior for both the CC and RAC beam specimens was very similar, essentially linear until failure. The cracking pattern for both the CC and RAC beam specimens was very similar, consisting of vertical flexural cracks at each end of the splice and horizontal splitting cracks along the splice region. The bond strength for the CC mix exceeded the RAC-50 mix by approximately 10%. The bond strength for the CC mix exceeded the RAC-100 mix by approximately 30%. General: The RAC mixes had enhanced bond strength with the reinforcing steel compared to the CC mixes when the failure did not result due to splitting, as evidenced by the pull-out specimens. However, when the failure was initiated by splitting of the concrete, the RAC mixes had lower bond strength compared to the CC mixes, as evidenced by the full-scale splice specimens. There is very good agreement between the concrete mechanical properties (splitting tensile strength and fracture energy) and the full-scale splice specimen test results, primarily due to the splitting type of failure mode.
