Study on fracture characteristics of steel fiber reinforced manufactured sand concrete using DIC technique

Incorporation of steel fibers to improve the defects of manufactured sand concrete (MSC) has received a great deal of attention, while the fracture mechanism of the MSC by volume fraction of steel fibers (V-f) has been less studied. To investigate the effects of steel fibers on the fracture characteristics of the MSC, three-point bending tests were conducted on the MSC beams with different V-f (0, 0.5 %, 1.0 % and 1.5 %) using digital image correlation technique. The effects of V-f on the fracture parameters and crack propagation paths of steel fiber reinforced manufactured sand concrete (SFRMSC) were analyzed. In addition, fracture process zone (FPZ) of the SFRMSC was analyzed via the length of the FPZ (l(FPZ)) and area of the FPZ (A(FPZ)). The results indicated that the residual strength, initiation fracture toughness, unstable fracture toughness, fracture energy and characteristic length of the SFRMSC increased with the increase of Vf, whereas the crack propagation paths were not sensitive to the changes of Vf. The addition of steel fibers increased the interaction between the aggregate and the matrix, which led to an increase in the number of microcracks. Before approaching the Pc, both the l(FPZ) and A(FPZ) showed essentially stable changes. As Vf increased, the l(FPZ) and A(FPZ )developed faster to their corresponding maximum values. The A(FPZ) reached a maximum and increased with the V-f. At the P-c, the lFPZ and AFPZ changed in a similar trend when V-f <= 1.0 %. When V-f > 1.0 %, the l(FPZ) changed slightly while the A(FPZ) increases sharply.