Fracture energy of steel fiber-reinforced concrete

Steel fiber-reinforced concrete (SFRC) is a cementitious material reinforce d with discrete fibers. The energy absorption capacity is the main material property benefited by fiber reinforcement. Closed-loop servo-controlled eq uipment should be used to evaluate this property. The tests should be carri ed out using displacement control in order to obtain the postpeak force-dis placement relationship (tensile strain-softening branch). To assess the fracture energy of SFRC, three-point bending tests were carri ed out using displacement control. Series of notched beams reinforced with 30, 60, and 90 kg/m(3) of hooked-end steel fibers were tested. Besides the energy dissipated in fracturing the concrete, the energy determined from th e force-displacement relationship can also include the energy absorbed duri ng nonlinear behavior of concrete in compression. Ductile materials, such a s concrete reinforced with a high content of fibers, develop large deflecti ons before exhausting their energy absorption capacity. In these cases, the "fixed" points of the bar supporting the displacement transducer may not r emain fixed, adding an extra deflection into the control displacement trans ducer and thus leading to incorrect evaluation of the fracture energy. Thes e factors are analyzed in the present work in order to assess the suitabili ty of the specimen dimensions and the test procedures for evaluating the fr acture energy of SFRC.