What Are the Performance Characteristics of Steel Fibers?

Understanding steel fiber

Steel fiber refers to fibers with a diameter-to-length ratio of 40 to 80, which are made by cutting fine steel wire, cutting cold-rolled steel strips, milling steel ingots, or rapidly cooling molten steel.

Properties of steel fiber

• High strength and hardness. Regardless of the manufacturing method, steel fiber is subjected to high heat and rapid cooling during processing, which is equivalent to a quenched state. Therefore, the surface hardness of steel fiber is high, making it unlikely to bend during mixing with concrete for reinforcement. If the steel fiber is too hard and brittle, it is also prone to break during mixing, which affects the strengthening effect.

• Improved mechanical properties. Steel fibers with regular alternation of circular and flat cross-sections can improve their mechanical properties.
  

• Corrosion resistance. The corrosion resistance test of steel fiber-reinforced concrete shows that the carbonized concrete at the crack and the corroded steel fiber in the carbonized zone will develop deeper carbonization depths and corrosion degrees over time in humid environments. Although the crack width is smaller than that of reinforced concrete, there are still cracks. Therefore, anti-corrosion measures should be taken for steel fiber-reinforced concrete used in humid environments, especially in seaside areas. Tests have shown that using larger-diameter steel fibers while ensuring that the load-bearing capacity of the concrete components remains unchanged can improve their corrosion resistance. Coating the steel fiber with epoxy resin or plating it with zinc can also improve its corrosion resistance. If the construction process allows, this type of steel fiber can be used only on the surface layer of the concrete (1-2 cm), or non-corrosive steel fibers can be used if necessary.
  

• Strengthening mechanism of Steel Fiber. There are two theoretical definitions of the strengthening mechanism of steel fiber-reinforced concrete: composite mechanics theory and fiber spacing theory. From different perspectives, these two theories explain the reinforcing effect of steel fiber, and their ultimate results are the same.
  

Composite mechanics theory of steel fiber: In the composite mechanics theory, steel fiber-reinforced concrete is seen as a fibrous reinforcement system. The stress, elastic modulus, and strength of steel fiber-reinforced concrete are calculated based on the mixing principle. Introducing the fiber direction coefficient based on the distribution and orientation of the fiber in the steel fiber matrix is essential to correctly select the fiber direction coefficient, which is one of the main factors affecting the fiber reinforcing effect. Fiber spacing theory of Steel Fiber: It has a restraining effect on the extension of cracks in concrete.