December 31, 2016
Reinforced concrete – a composite material where the low tensile strength of concrete is compensated by the high tensile strength of steel – is widely used on virtually any type of structure.
It has been successfully used because of the many well-known advantages steel provides. However, certain properties of steel, like electrical and thermal conductivity, magnetism, and most importantly, low resistance to corrosion, may negatively affect the performance of reinforced concrete structures.
Depending on the type and conditions of a structure, these properties may be from irrelevant to detrimental to the structural performance. One typical example where corrosion is of high importance, are reinforced concrete bridges, especially when exposed to de-icing salts. Corrosion of steel reinforcement increases the maintenance cost considerably, and it affects aesthetics up to structural collapse if not properly maintained.
Epoxy coated steel and stainless steel have been widely used as corrosion resistant reinforcement. Epoxy coated steel however has not performed as expected since it still corrodes. While stainless steel performs well, it comes at a high price.
A relatively recent solution, increasingly used as corrosion-resistant reinforcement, are Fiber Reinforced Polymers, with Glass Fiber Reinforced Polymers providing the best value in terms of ratio of cost to mechanical properties.
Being a relatively new material compared to steel, there is still skepticism within the engineering community. Extensive research has been carried out at various research institutions across the world. The specimens range from single GFRP bars to full-scale applications like the crash test of a TL-5/PL-3 barrier wall, by the Texas Transportation Institute. As you can notice in the following video, the performance of the GFRP reinforced barrier wall exceeds all requirements.
More information on the material can be found on the websites of various GFRP manufacturers, like Fiberline Composites, Pultrall, etc. If you need to design FRP reinforced concrete structures, Delta Innoveering is always available to help.