Fiber reinforced concrete, often abbreviated as FRC, is a specialized type of concrete comprising cement, aggregates, and a specified proportion of fibers. These fibers serve the purpose of reducing permeability, bleeding, and the formation of minor cracks within the concrete. Additionally, they enhance the tensile strength and impact resistance of the material.
The effectiveness of fiber reinforcement depends on various factors including the type of fiber material, its shape and size, as well as the volume and distribution pattern within the concrete mix.
Different types of fibers are employed in the production of fiber reinforced concrete. These include steel fibers, glass fibers, asbestos fibers, polypropylene fibers, carbon fibers, and organic fibers. Fiber-reinforced concrete is primarily categorized into two main types:
1. Steel Fiber Reinforced Concrete (SFRC):
Steel Fiber Reinforced Concrete, abbreviated as SFRC, involves the incorporation of small amounts of steel fibers into the concrete mix. These steel fibers are typically derived from low carbon steel wires, with lengths ranging from 10-60 mm and diameters of 0.25-0.75 mm. In addition to round fibers, flat steel fibers are also commonly used, created by cutting plates of 0.15-0.40 mm thickness and widths ranging from 0.25-0.90 mm, with lengths of 10-60 mm.
However, steel fibers have a tendency to clump together, posing challenges in ensuring their uniform random distribution within the concrete. This issue is addressed by using fiber bundles, where the steel fibers separate during the concrete mixing process and are subsequently dispersed randomly within the mix.
By incorporating 2 – 3% fibers (by volume), a notable increase in the flexural strength of the concrete, as well as improvements in crack resistance, explosion resistance, and other properties, can be achieved.
Applications of SFRC:
SFRC is particularly well-suited for applications in the construction of pavements, bridge decks, pressure vessels, tunnel linings, and more.
2. Glass Fiber Reinforced Concrete (GFRC):
Glass fibers are typically composed of 200 – 400 individual filaments lightly bonded together to form a strand. These strands are then sheared into varying lengths to create cloth, mat, and tape.
The addition of 10% fiberglass to concrete can lead to a twofold increase in tensile strength and impact resistance. It’s worth noting that when employing the conventional mixing method, only 2% of fibers can be integrated at a length of 25 mm. Furthermore, the strength of glass fiber is significantly enhanced as its diameter decreases.
While small diameter glass fibers exhibit high tensile strength, they are also quite brittle and unsuitable for longer spans. Additionally, glass fibers are susceptible to corrosion from the alkali present in Portland cement. To utilize glass fibers as micro reinforcement, they must undergo proper treatment, such as an epoxy resin coating.
Applications of GFRC:
GFRC is predominantly utilized in the production of precast products like spun pipes and wall cladding.
