A brief introduction to FRP composites
Fiber reinforced polymer (FRP) is a multiphase material consisting of high strength fibers embedded in a polymer matrix. The strength and unique properties of FRP composites were initially tested and utilized by the aerospace industry in the 1960s. Following the exceptional performance in the aerospace industry, FRP composites started displaying their potential in building new concrete structures and maintaining the existing concrete structures in the late 1990’s. As compared to traditional construction materials such as steel, FRP composites offer highly desirable and unique properties.
The construction industry cannot accept a material until its properties are thoroughly tested and proven. Extensive research at various national and international levels pave the way for composites to address the contemporary construction problems.Today, one of the biggest concern for the construction industry is the inability of conventional materials to address deterioration related issues. FRP composites, also called the material of 21st Century, has the solution civil engineers have been looking for.
Properties of FRP Composites
The mechanical and physical properties of FRP composites depends largely upon its constituents and the manufacturing process. The role of fibers is to provide strength and stiffness while polymeric matrix ensures environmental protection and contributes to load transfer. The role of additives and modifiers is to deal with surface smoothness, crack resistance, and the overall performance of FRP bars. Some of the leading properties of FRP composites include:
- High tensile strength
- High strength-to-weight ratio
- Excellent bond strength
- No susceptibility to corrosion
- Electrically and thermally non-conductive
Deterioration: a growing concern
Worldwide deterioration of traditional material such as black steel is a growing concern for governments. More than 50,000 bridges in the US are structurally deficient and need to be either replaced or rehabilitated. There is an unprecedented need for rust free construction materials. Being a potential solution to this rising problem, FRPs are gaining rapid recognition from the civil engineering community. One of the growing applications of FRP composites is the rehabilitation of degraded concrete structures.The construction agencies can extend the service life of concrete infrastructure by using FRPs as external reinforcement materials.
Environmental durability of FRP composites
The effects of corrosion on the service life of reinforced concrete structures The advanced composite materials have produced results in terms of environmental durability. Civil engineering projects such as highways, bridges, waterways, and marine structures play a decisive role in building a healthy and sustainable economy. Concrete deterioration costs the construction agencies billions of dollars as a direct maintenance cost. Over the past couple of decades, FRP composites have gained considerable popularity as an ideal material for rehabilitation applications. However, rehabilitation of existing concrete members is just an application of FRP composites.
A full-scale use of FRP bars enables civil engineers to build environmentally protected projects that can withstand the impact of the harsh environment.FRP materials are increasingly being used in civil engineering applications such as reinforcing rods and tendons, wraps for seismic retrofit of columns externally bonded reinforcement, composite bridge decks, and even hybrid and all composite structural systems. Since FRP are still relatively unknown to the infrastructure system planner, there are heightened concerns related to the overall durability of these materials, especially as related to their capacity for sustained performance under harsh and changing environmental conditions under load.
Sustainable concrete infrastructure
According to stats, around 50% of the construction budget is spent on the rehabilitation of existing concrete infrastructure in Europe. Rehabilitation is a broad term that includes repair, inspection, maintenance, and seismic retrofitting. Hidden costs such as traffic delay cost are around 20% of the total construction cost. Concrete structures reinforced with traditional means need to be maintained and upgraded in order to make them sustainable.
Sustainable construction materials and techniques can help governments build structures with long service life without spending too much on maintenance. It is hard for a country to progress if its concrete infrastructure is not stable and durable.
How can FRP composites help?
As discussed earlier, FRP composites perform exceptionally well under heavy loads and severe environment. A building reinforced with fiberglass rebar hardly need any maintenance. Therefore, the construction industry must adopt modern materials to build concrete structures that can serve for a long period of time.
The ideal applications of FRP composites
Civil engineering applications of GFRP bars or FRP composites are:
- Any concrete member that is susceptible to chloride ions and chemicals
- Applications require thermal neutrality: research laboratories, health facilities, military applications.
- Mining and tunneling where machinery will consume the reinforced structures
- Applications which demand electromagnetic neutrality
The Peace Bridge in Canada was built using GFRP reinforcement
Rehabilitation of Concrete Columns With FRPs
The purpose of confining concrete is to improve its strength, durability, and overall performance. In past, longitudinal steel bars and concrete were added around existing structure to enhance reinforced concrete columns. In addition, a steel jacket was applied to a concrete column to add some extra strength to the structure. However, these conventional rehabilitation techniques were difficult to carry out.
High-strength fiber composites have been extensively and successfully tested and applied as an effective and durable material for the external confinement of concrete. Confinement of concrete with polymer composites sheets have demonstrated excellent results when it comes to compression and sustainability. Fiber-wrapping of existing concrete as a rehabilitation measure and encasement of concrete with advanced composites for new projects are two modern ways of confining concrete columns. The application of wrapping can be either continuous over the surface or as strips.
The composite wrapping systems have largely been used in North America and Japan for seismic loading and rehabilitation of bridges. The growing awareness for corrosion-free construction materials has really promoted the use of fiber reinforced polymers throughout the world.
FRP bars in a bridge deck
FRP reinforcement techniques
The construction industry started using advanced composite materials in the 1970s. Extensive research has been carried out in order to enhance certain physical properties of FRPs. Industrial research and the use of composite materials have broadened the scope and applications of fiber-reinforced construction material. Following are some of the FRP reinforcement techniques:
It is financially convenient to repair or strengthen a concrete structure than to build a new one. FRP reinforcement material is widely used to repair and strengthen structurally deficient structures like bridges, buildings, and other concrete members.
There are several rehabilitation techniques that engineers use to rehabilitate a concrete member with fiber-reinforced polymers. Following are some of the techniques that use GFRP and other FRP variants to rehabilitate a deteriorated member.
- Bonding of the FRP plates to the adhered
- Unstressed FRP Flexural plates bonded in a position
- Near-surface mounted FRP reinforcement
- Flexural strengthening of prestressed structures
- Seismic retrofitting of reinforced concrete
For internal reinforcement of concrete members, FRP bars are fabricated using a pultrusion method. It is inevitable to prepare the bars made of fiber, carbon, or aramid in order to develop an excellent bond characteristics between bars and concrete. First, a peel-ply can be applied to the surface of fiberglass bars in the manufacturing process; a rough surface of the pultruded bars brings about good bonding.Second, pultruded bars can be over-winded with fibers. Third, a layer of sand can be bonded with the adhesive to the surface of pultruded bars.
Healthy concrete infrastructure saves money and time for both government and tax payers. The initial cost of using FRP composites might be high. However, the long-term performance and minimal maintenance cost make FRP composites as highly cost-effective and sustainable construction material. New design codes, in-practice statistics, and extensive research has encouraged the construction industry to use advanced composites (FRP) for building sustainable concrete members.
FRP Rebar Manufacturer in North America
North America is the largest producer and consumer of FRP composites. TUF-BAR is one of the leading GFRP fiberglass bars manufacturers in the region. The company produces highest-quality fiberglass construction material including Rebar, Rock Bolts, Form Ties and Concrete Anchors which are corrosion free, strong and lighter alternative to traditional steel reinforcement. TUF-BAR fiberglass bars are specified for use in roadways, bridges, dams, concrete slabs, barrier walls, marine applications, tunneling, temporary applications, and power generation facilities. For details, please visit our website (PRODUCTS SECTION) or one of our offices in Canada and United States. Location details can be found on our website’s Contact Us page.