Mechanical behavior of concretes containing waste steel fibers recovered from scrap tires

The paper presents the results of an experimental program in which steel fibers recovered from scrap tires were used to produce fiber reinforced concretes. Waste fibers having different geometrical characteristics were used in the mixtures at different percentages. To have reference concretes, a plain mixture without fibers and one mixture containing a commercial steel fiber were also prepared. Some mechanical properties such as compressive strength, splitting strength and flexural strength were determined. Load-deflection behaviors including the post-peak responses were monitored by means of a closed-loop bending test set-up. Test results showed that the fibers recovered from scrap tires affected the mechanical behavior of concrete similar to the commercial fibers. Depending on the geometrical properties of the fibers and fiber content, the descending branch of the load-deflection curves were modified with the use of waste fibers, thus affecting the toughness of the concretes. Comparison of these curves indicated that the performances of the waste fibers were lower when compared to the commercial fiber used. Based on the test results obtained and the relative costs of the mixtures, a multi-objective simultaneous optimization technique was also performed to determine the optimum fiber type and content. This procedure indicated that the use of waste fibers can be optimized for producing fiber reinforced concrete.