EFFECTS OF THE FIBER VOLUME CONTENT ON THE WORKABILITY, STRENGTH, AND ELECTRICAL RESISTIVITY OF HIGH-PERFORMANCE CONCRETES

Abstract

This study investigated the effects of steel fiber content on the workability, strength, and resistivity of high-strength concrete. Smooth straight steel fibers with a diameter of 0.2 mm, length of 13 mm, brass coating, tensile strength of 2100 MPa, and elastic modulus of 200 Gpa reinforce high-strength concrete. The steel fiber content used in the F0, F2, F4, and F5 matrices is 0, 2%, 4%, and 5%, respectively. Test results showed that, as the steel fiber content increased from 0 to 2%, the workability of the concrete mixture and the compressive strength little changed. As the steel fiber content increased from 2% to 4% and 5%, the workability of the concrete mixture decreased while the compressive strength of the concrete increased. The flow values of F0, F2, F4, and F5 are 245 mm, 240 mm, 220 mm, and 200 mm,  respectively while the compressive strength is 98.5 MPa, 102.3 MPa, 110.14 MPa, and 117.97 MPa, correspondingly. The volumetric weight increased from 2237.3 kg/m3 to 2584 kg/m3 as the steel fiber content increased from 0 to 5%. The electrical resistivity of concrete significantly decreased as the steel fiber content increased from 2% to 4% but decreased slightly as the fiber content increased to 5%. The microstructure images of concrete surrounding steel fibers and the distribution of steel fibers were captured and analyzed. Then the conductive network model in steel fiber-reinforced high-performance concrete was analyzed and explained. Steel fiber content of 4% can be considered as the percolation threshold in high-strength concrete for evaluating the sensing ability under the effect of external load.