Report on Fiber-Reinforced Polymer (FRP) Reinforcement for Concrete Structures
|Publication Date:||1 September 2007|
Fiber Reinforced Plastic (FRP) products were first used to reinforce concrete structures in the mid 1950s (Rubinsky and Rubinsky 1954; Wines et al. 1966). Today, these FRP products take the form of bars, cables, 2-D and 3-D grids, sheet materials, plates, etc. FRP products may achieve the same or better reinforcement objective of commonly used metallic products such as steel reinforcing bars, prestressing tendons, and bonded plates. Application and product development efforts in FRP composites are widespread to address the many opportunities for reinforcing concrete members (Nichols 1988). Some of these efforts are:
• High volume production techniques to reduce manufacturing costs
• Modified construction techniques to better utilize the strength properties of FRP and reduce construction costs
• Optimization of the combination of fiber and resin ma trix to ensure optimum compatibility with portland cement
• Other initiatives which are detailed in the subsequent chapters of this report
The common link among all FRP products described in this report is the use of continuous fibers (glass, aramid, carbon, etc.) embedded in a resin matrix, the glue that allows the fibers to work together as a single element. Resins used are thermoset (polyester, vinyl ester, etc.) or thermoplastic (nylon, polyethylene terephthalate, etc.). FRP composites are differentiated from short fibers used widely today to reinforce nonstructural cementitious products known as fiber reinforced concrete (FRC). The production methods of bringing continuous fibers together with the resin matrix allows the FRP material to be tailored such that optimized reinforcement of the concrete structure is achieved. The pultrusion process is one such manufacturing method widely practiced today. It is used to produce consumer and construction products such as fishing rods, bike flags, shovel handles, structural shapes, etc. The pultrusion process brings together continuous forms of reinforcements and combines them with a resin to produce high-fiber volume, directionally oriented FRP products. This, as well as other manufacturing processes used to produce FRP reinforcement for concrete struc tures, is explained in more detail later in the report.
The concrete industry's primary interest in FRP reinforcement is in the fact that it does not ordinarily cause durability problems such as those associated with steel reinforcement corrosion. Depending on the constituents of an FRP composite, other deterioration phenomena can occur as explained in the report. Concrete members can benefit from the following features of FRP reinforcement: light weight, high specific strength and modulus, durability, corrosion resistance, chemical and environmental resistance, electromagnetic permeability, and impact resistance.
Numerous FRP products have been and are being developed worldwide. Japan and Europe are more advanced than the US. in this technology and claim a larger number of completed field applications because their systematic research and development efforts started earlier and because their construction industry has taken a leading role in development efforts.