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Fibers and their different variables when choosing the right one

Five key elements to choose the right fiber for your next project

Type of application

Fiber serves different functions depending on the type of element in which it is used. For pavements, fibers like r hook 50 can replace traditional mesh for covering structural requirements such as bending, punching, and fatigue forces.

In the case of shotcrete, which is used in tunnels and slopes, fibers are dosed to increase energy absorption capacity and meet the requirements of rock classification. Very short and slender fibers, such as rhook35, can provide the necessary energy absorption, which is why length is not a critical parameter.

In prefabricated and other structures, fibers are primarily dosed to prevent cracks due to shrinkage and reduce defects that occur during manufacturing and transportation.

Responsability in load

A key factor in choosing the type of fiber is its structural responsibility. If you intend to use it as the sole reinforcement element, such as in pavements or certain types of prefabricated items like concrete pipes, you should first analyze the loads and determine whether they are high or not for that application.

When the loads are very high, typically fibers like r glued are used, which provide the largest surface area and the best anchorage. This is achieved with long fibers, smaller diameter, and high tensile strength. If the requirements are not very high, structural polymeric fibers can be an economical option. When only fiber is needed to control shrinkage, synthetic microfibers, like r micro PP, help with water retention, contributing to better curing and supporting the matrix when it has not fully consolidated.


If the aesthetic finish of the element is important, it is advisable to use twisted or multifilament fibers. These fibers can have more than 20 filaments per unit and are flexible, so their individual diameter is smaller, they disperse easily, and troweling equipment allows for a high-quality finish. When aesthetic appearance is not critical but the concrete will be exposed, metallic fibers allow for a quick and aesthetic finish. When considering placing a wearing layer on the concrete pavement, any fiber that meets structural requirements is suitable.

Exposure Environment

Synthetic and glass fibers have high chemical resistance, so they perform excellently in environments with aggressive compounds, such as fertilizers storage pavements. Metallic fibers can experience surface degradation in a saline environment, but if the concrete does not have microcracks and is properly compacted, the fibers will perform adequately over time.

Layer Thickness

For thin elements demanding high strength, like Ultra-High-Performance Concrete (UHPC), r smart is the appropriate fiber. Its use in high dosages increases the ductility of the elements and can cover large spans without deformations over time or flexural failure. The fiber should maintain a 1/3 relationship with respect to the thickness of the element for proper dispersion. For this reason, in thicknesses less than 15 cm, it is advisable to use short fibers, ensuring that the concrete also has a 1/3 smaller aggregate size. In elements with greater thickness, there is no restriction on fiber length.

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