For indoor applications such as tunnels and warehouses, no. For outdoor applications such as pavements some minor rusting may occur. experience in highways and industrial pavements indicate that while individual fibers corrode at the surface, staining of the concrete surface does not occur. overall aesthetics and serviceability are maintained even with the presence of individual fiber corrosion. indoor Applications- Surface fibers in typical indoor tunnels or manufacturing floor applications remain bright and shiny under normal environmental conditions.
Outdoor Applications Without cracks- experience has shown that concrete specified with a 28-day compressive strength over 3000 psi, mixed with standard water/cement ratios, and installed with methods that provide good compaction, limit the corrosion of fibers to the surface skin of the concrete. When surface fibers corrode, there is no propagation of the corrosion more than 0.008” beneath the surface. Since the fibers are short, discontinuous, and rarely touch each other, there is no continuous path for stray or induced currents between different areas of the concrete. outdoor Applications With cracks-laboratory and field-testing of cracked SFrc in environments containing chlorides has indicated that the cracks in concrete can lead to corrosion of the fibers passing across the crack. However, small cracks (crack widths < 0.008”) do not allow corrosion of steel fibers passing across the crack. if the cracks wider than 0.008” and are limited in depth, the consequences of this localized corrosion are not structurally significant.
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Steel fibers mixed into the concrete can provide an alternative to the provision of conventional steel bars or welded fabric in some applications. The concept has been in existence for many years (the first patent was applied for in 1874), and it has been used in a limited range of applications: among the first major uses was the patching of bomb craters in runways during World War II. However, it was during the 1970s that commercial use of this material began to gather momentum, particularly in Europe, Japan and the USA.
Today, industrial floors and pavements are major applications for steel-fiber-reinforced concrete. In the United Kingdom, several million m2 of steel-fiber-reinforced slabs have been installed over the past ten years, both for ground-supported and pile-supported floors. Other major applications for fiber-reinforced concrete include external paved areas, sprayed concrete, composite slabs on steel decking and precast elements.
Fibers are often used to replace the nominal conventional steel fabric in ground bearing slabs. Steel fibers are increasingly being used in suspended ground floor slabs on piles to replace much, and in many cases all, of the reinforcement. Savings in the cost of supplying and fixing the conventional welded fabric reinforcement that is replaced can offset the extra cost of adding fibers to the concrete. There may also be health and safety benefits resulting from the reduced handling of reinforcement. Also, problems caused by the misplacement of conventional steel in the depth of the slab are avoided.