Shear strength of steel fiber-reinforced concrete

The shear behavior of fiber-reinforced concrete was studied using direct shear tests. Two 50 mm-long steel fibers, one with flattened ends and a circular cross section and the other with a crimped geometry and a crescent cross section, were investigated at fiber volume fractions varying between 0 and 2%. Direct comparison was made with flexural toughness determined as per the ASTM C 1018 procedure. It was found that both fibers provided significant improvements in shear strength as well as shear toughness and these improvements were greater at higher fiber dosage rates. Between the two fibers, the fiber with flattened ends was seen to be more effective than the one with crimped geometry. For the flattened-end fiber an almost linear increase in the shear strength was noted with an increase in the fiber volume fraction. For the fiber with crimped geometry, on the other hand, shear strength approached a plateau value beyond which no increases in shear strength occurred with an increase in the fiber volume fraction. While plain concrete failed at a low equivalent shear strain of 0.4%, fiber-reinforced concrete supported as high as 10% strain in shear. When the shear toughness of steel fiber-reinforced concrete was compared with its flexural toughness, there appeared to be a direct correlation. However given the subjectivity of this type of comparison and the limited data generated in this study, much further research is needed to fully understand and establish this correlation.