Fiber reinforced concrete is a composite material composed of Portland cement, aggregates, and fibers. Ordinary unreinforced concrete is brittle and has lower tensile strength and strain capacity. The role of randomly distributed irregular fibers is to fill cracks in composite materials. Fibers are commonly used in concrete to control plastic shrinkage cracks and dry shrinkage cracks. They also reduce the permeability of concrete, thus reducing water flow. Certain types of fibers produce greater impact, wear, and resistance to fragmentation in concrete. Fibers usually do not improve the flexural strength of concrete. The amount of fiber required for concrete mix proportions is usually determined as a percentage of the total volume of composite materials. The combination of fibers and materials allows fiber-reinforced concrete to withstand considerable stress during the post cracking stage. The actual function of fibers is to improve the toughness of concrete.
Steel fiber reinforced concrete and its application
In recent years, steel fiber reinforced concrete has gradually developed from a new and unproven material to a recognized material in many engineering applications. In recent years, it has become increasingly common to replace steel bars with steel fiber reinforced concrete. The application of steel fiber reinforced concrete is extensive and diverse, making it difficult to classify. The most common applications are tunnel lining, flat slabs, and airport pavement.
Many types of steel fibers are used for concrete reinforcement. Round fibers are the most common type, with a diameter between 0.25 and 0.75 millimeters. The thickness of rectangular steel fibers is usually 0.25 millimeters, although India has already used steel wires ranging from 0.3 to 0.5 millimeters. The form of deformed fiber bundles is also used. The main advantage of deformable fibers is that they can be uniformly distributed in the matrix. Fibers are relatively expensive, which to some extent limits their use.
The following are some properties that can be significantly improved by using steel fibers:
Bending strength: Compared with traditional concrete, the bending strength can be increased by more than three times.
Anti fatigue performance: The fatigue strength increases by nearly half.
Impact resistance: It has greater resistance to damage in the event of severe impact.
Permeability: The porosity of the material is relatively small.
Wear resistance: More effective ingredients to resist wear and peeling.
Shrinkage: can eliminate shrinkage cracks.
Corrosion: Corrosion may affect materials, but it can be restricted in certain areas.
Limitations of Steel Fiber Reinforced Concrete
Although steel fiber reinforced concrete has many advantages, there are also some problems that need to be thoroughly solved.
The uniform dispersion of fibers and the consistency of concrete properties involve some complex issues.
Compared to ordinary concrete, using SFRC requires more precise configuration.
Another issue is that the required improvements cannot be achieved unless steel fibers are added in sufficient quantities.
However, as the number of fibers increases, the workability of concrete is affected. Therefore, steel fibers use special processes and concrete mixtures. If appropriate techniques and proportions are not used, fibers may also lead to surface treatment issues, and fibers may emerge from the concrete.