Bond of steel reinforcing bars in self-prestressed hybrid steel fiber reinforced concrete

Reinforcing bar bond is of paramount importance for the structural integrity of reinforced concrete and can be enhanced by fiber inclusion and self-prestressing. Previous research has developed bio-inspired self-prestressed fiber reinforced concrete (SP-FRC) utilizing fibers and expansive agent, and multiscale hybrid steel fiber reinforced concrete (HSFRC). In this research, SP-FRC and HSFRC were combined to develop bio-inspired self-prestressed hybrid steel fiber reinforced concrete (SP-HSFRC) in which the bond of steel reinforcing bars was studied experimentally by pull-out tests. From the bond-slip curves, various bond parameters, namely, bond strength, slip at peak bond stress, initial bond stiffness, and secant bond stiffness, were determined and correlated to a hybrid fiber factor to establish analytical models for design calculations. Then, a new bond model that yields finite initial bond stiffness for more realistic bond-slip analysis than the Model Code 2010 was extended to SP-HSFRC, as evidenced by good agreement between the predicted and experimental bond-slip curves. Lastly, the beneficial effect of the improved bond in crack control of steel bar reinforced HSFRC was rigorously proved.