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.