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

Abstract

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 (Vf) 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 Vf (0, 0.5%, 1.0% and 1.5%) using digital image correlation technique. The effects of Vf 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 (lFPZ) and area of the FPZ (AFPZ). 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 lFPZ and AFPZ showed essentially stable changes. As Vf increased, the lFPZ and AFPZ developed faster to their corresponding maximum values. The AFPZ reached a maximum and increased with the Vf. At the Pc, the lFPZ and AFPZ changed in a similar trend when Vf ≤ 1.0%. When Vf > 1.0%, the lFPZ chang…