Effect of fly ash replacement level on the bond strength of reinforcing steel in concrete beams

This study compares the bond strength of reinforcing steel in high-volume fly ash concrete (HVFAC) mixes. Three mixes with 0% (conventional concrete), 50%, and 70% replacement of Portland cement with a Class C fly ash investigated in this study. Three beams (simply supported four-point loading condition) as well as three pull-out specimens (based on RILEM recommendations) were tested for each mix. Test results evaluated based on different codes as well as a bond database of conventional concrete specimens. These comparisons indicate that with increasing replacement level of fly ash in concrete the bond strength of reinforcing steel in concrete increases. Results of this study show that the increase in basic mechanical properties (splitting tensile strength, flexural strength, and fracture energy) for the HVFAC parallels the increase in full-scale bond behavior and can be used as a predictor in mixes containing fly ash. •HVFAC possesses reinforcement bond strength comparable or slightly greater than CC.•Load-deflection behavior of the HVFAC and CC beams was essentially identical.•No significant difference between load-slip behavior of the HVFAC and CC specimens.