Abstract
Fiber reinforcement of concrete is an effective technique of providing ductility to concrete, increasing its flexural residual strength while reducing its potential for cracking due to drying shrinkage. There are currently a wide variety of industrial fibers on the market. Recycled steel fibers (RSF) from tires could offer a viable substitute of industrialized fibers in a more sustainable and eco-friendly way. However, mistrust exists among users, based on fear that the recycling process will reduce the performance, coupled with the difficulty of characterization of the geometry of the RSF, as a consequence of the size variability introduced by the recycling process. This work compares the behavior of RSF from tires compared with industrialized steel or polypropylene fibers, evaluating the fresh state, compressive strength, flexural residual strength, and drying behavior. The concept of Equivalent Fiber Length (EFL) is also defined to help the statistical geometrical characterization of the RSF. A microstructural analysis was carried out to evaluate the integration of the fiber in the matrix, as well as the possible presence of contaminants. The conclusion is reached that the addition of RSF has a similar effect to that of industrialized fibers on concrete’s properties when added at the same percentage.
Highlights
Recycled steel fibers (RSF) from tires were used in this paper for internal reinforcement of concrete
In order to establish the performance of RSF with respect to those widely used in concrete, two of the most common types of fibers used in fiberreinforced concrete were selected, such as polypropylene monofilament fibers to control cracking (Figure 3a), and steel fibers (Figure 3b) to provide residual strength after cracking of concrete
The sizes of the bins were established at 0.05 mm for diameters and 5 mm for Equivalent Fiber Lengths
Summary
Concrete is undoubtedly the most common building material in use today. Its use encounters certain drawbacks, the main one being its brittleness, i.e., its low tensile strength compared to its compressive strength, its low deformation capacity until the appearance of the first crack, along with its rapid propagation. Since ancient times, building materials, e.g., clay sun baked bricks, were reinforced with fibers such as horse-hair, straw, and other vegetable fibers to try to overcome this hindrance. The brittle matrix supports, surrounds and protects the fibers, providing compressive strength, while the fibers enhance the mechanical response of the composite by bridging the cracks that appear after tensile failure and providing a sort of ductile behavior post cracking
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