Bond strength of deformed reinforcement embedded in steel fiber reinforced concrete: Influencing factors and prediction model

The addition of steel fiber is an effective method to improve the bond behavior between reinforcement and concrete. However, a unified bond strength model for bond strength of reinforcement in steel fiber reinforced concrete (SFRC) is not available yet. In this paper, the effect of the related factors on the bond strength is first analyzed and then a modified bond strength is proposed, based on 449 test data collected from 18 bond experimental studies. The influencing factors considered include bond test methods, cover to rebar-diameter ratio (c/d), bond length to rebar diameter ratio (l/d), fiber fraction (V-f), fiber slenderness (l(f)/d(f)) and rebar diameter (d). The results indicate that bond strength is greatly affected by c/d and l/d, while the effect of steel fiber is correlated with the composite fiber factor (V-f & sdot;l(f)/d(f)) and fiber distribution uniformity. In addition, the applicability of five SFRC bond strength models proposed previously is evaluated based on statistical characteristics. Current bond strength models have limited applicability and some models inappropriately neglect the effect of bond length. A modified bond strength model with improved goodness-of-fit and prediction accuracy is proposed which has good applicability to both pullout and beam bond tests.