Pros and Cons of Fibre Mesh Concrete

Fiber mesh concrete, or fiber reinforced concrete, is an alternative to steel-reinforced concrete. What are the advantages of fiber mesh concrete, and how does it work?

What Does Fiber Mesh Do For Concrete?

Fiber mesh concrete incorporates fibers into the concrete mix design at the job site. These fibers can vary in shape, size, and material, depending on the purpose they serve in that project.

Does Fibre Mesh Add Strength to Concrete?

Concrete is incredibly strong in compression, but its tensile strength rates at one-tenth of that value. Adding macrofibres to the concrete mix design improves flexural strength. When done correctly, the tensile strength could increase by quite a large margin, nearly matching that of the compressive strength in some cases.

What Types Of Fibres Are Used in Concrete?

Fibers in concrete are divided into two categories according to size: microfibers and macro fibers. Microfibres are tiny, up to 10mm in length, and don’t add strength to hardened concrete. Instead, these fibers minimize bleeding in fresh concrete, potentially eliminating hairline cracks associated with excessive bleeding. Microfibers are generally made of synthetic materials or polymers and are soft to the touch. Their texture is similar to that of synthetic hair, almost like doll’s hair.

Macrofibres are larger than microfibers, up to 50mm in length, and are made of metals or synthetic polymers. These are stiff, strong fibers with a ridged or stepped profile to better grip the hardened concrete. Macrofibres add tensile strength to cement-concrete mix designs – more on this in the next section.

Nowadays, synthetic fibers are just as strong as their metallic counterparts – even stronger, in some cases. The benefit of synthetic fibers often renders them preferable to the metallic version since they are sometimes cheaper to manufacture, and they are corrosion resistant.

Here’s how this works: macro fiber profile shape lends itself to concrete gripping to it. As mentioned above, these fibers have a ridged and often stepped profile. As the concrete hardens, it grips onto this profile, properly entrenching the fibers into the concrete’s crystalline structure. When a crack forms in the concrete, its spread is halted by these fibers. Here, the fiber effectively keeps the two sides of the crack together. Extensive research in this regard shows that fibers are highly effective in this regard.

In floor slabs, fiber reinforced concrete often requires fewer joints than its unreinforced or steel mesh reinforced counterparts. Here, the fiber adds enough flexural strength to prevent shrinkage cracks. It also enables the concrete to bear a more significant point load, like the case in warehouse floors with heavy forklift traffic. In warehousing applications, the design engineer should avoid construction joints and any other form of joint since these become sites for localized surface damage. Here, the hard forklift wheels wear out the joints’ sides, causing the concrete to crumble and crack. These cracks spread, causing significant damage to the floor structure. Simultaneously, these damaged areas cause damage to the forklift wheels, which the building owner must replace. This situation creates an unnecessary expense for the warehouse management company.

Fibre Mesh Concrete Pros And Cons

Pros and Cons of Fiber Mesh Concrete

Advantages of Fiber Reinforced Concrete

  • Fiber mesh reduces shrinkage and cracking of concrete.
  • Similar to other reinforced concrete, it improves the tensile strength of concrete.
  • Reduces the chance of spalling since the fiber inside melts and allows the water content in concrete to escape.
  • It is easy to include fibers in the concrete mix design.
  • Polymer fiber reinforcement offers better corrosion resistance compared to steel reinforced concrete.

Disadvantages

  • clumping: Steel fibers are prone to clumping in ready-mix trucks, leading to balls of fiber concentrated in one portion of the pour, with no fiber present in other areas.
  • Cost: The fiber mesh concrete often costs more than rebar and wire-mesh concrete.
  • Depending on the type of fiber material, the surface texture can be fuzzy and hence difficult to paint. You may need to use a floor polisher before you can paint or do epoxy flooring.

Fibre Mesh Concrete vs Rebar

Is fiber mesh better than rebar?
The fibers are usually packaged in a water-soluble bag dropped into the back of a ready-mixed concrete truck while mixing is underway. This fresh concrete is poured and placed at the job site like any other, with little to no change in its workability and consistency. Generally, fiber concrete is easy to work with and makes for easy placement compared to steel-reinforced concrete. It also saves time and space on site since there won’t be piles of steel mesh stored on-site and no time-consuming set-up of this mesh.

That said, these fibers must be added to the back of the ready-mix truck slowly, allowing for proper dispersion, or polymer fibers should be used instead of steel to avoid clumping. Polymer fibers are not prone to clumping and generally disperse evenly through the entire batch of wet concrete.

Conversely, including rebar in a concrete structure is highly work-intensive and requires precise site practices. When placed correctly, rebar, or steel reinforcement, lends extensive flexural strength to the structure. However, when things go wrong, and placement is done incorrectly, steel reinforcement could weaken the structure since it then adds weight to the wrong part of the structure without increasing the tensile strength in the areas most needed.

Should I Put Fiber in My Concrete?

Fiber mesh concrete is easy to work with and, when used in floor slab applications, could easily replace traditional steel-reinforced concrete. It is also quicker and much easier to use at the job site. The key here is to use the correct fibers for each application. The mix design engineer must choose between micro-and macro fibers and between steel and synthetic fibers, each of which is suited to specific applications and performance parameters.