Bond of reinforcing bars to steel fiber reinforced concrete

Steel fiber reinforced concrete (SFRC) has been increasingly used during recent years. Regarding bond of rebars to concrete, fibers provide passive confinement and improve bond capacity in terms of bond strength and, more importantly, toughness. An extensive experimental programme has been carried out, and SFRC specimens with embedded rebars have been subjected to the Pull Out Test to obtain the bond stress-slip curves, retaining the bond strength and the area under the curve as measures of the bond capacity of concrete. The following parameters were considered: concrete compressive strength (30-50 MPa), rebar diameter (8-20 mm), concrete cover (between 30 mm and 5 times rebar diameter), fiber content (up to 70 kg/m3), and the slenderness and length of the steel fibers used. Predictive equations have been obtained to relate the experimental results to the factors considered, and the trends observed have been analyzed and discussed.