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GFRP rebar

GFRP rebar

The development of composite reinforcement can be traced back to the period after World War II. Thanks to their high strength and light weight, composite materials gained recognition in the aerospace industry. The positive results achieved in the aerospace and defense sectors, which peaked during the Cold War, led to even broader applications of composites. At that time, the United States needed affordable materials to support its rapidly growing economy. The development of fiber-reinforced polymers made it possible to produce components with consistent cross-sectional profiles. Continuous fiber composite polymers were initially used in the manufacturing of fishing rods and golf club shafts. It was not until the 1960s that composite materials started to be seriously considered for construction as an alternative to steel reinforcement.
One of the first and most notable Glass Fiber Reinforced Polymer (GFRP) projects was completed during the 1950s. The Massachusetts Institute of Technology (MIT) completed a house design crafted entirely from fiber-reinforced polymer. The carefully designed GFRP house, constructed in 1956, was situated in Tomorrowland at Disneyland in the United States. For a full decade, Disney’s FRP home of the future welcomed countless visitors and was a very popular attraction. In 1967, it was decided that the House of the Future would be replaced by another attraction. Amazingly, when the wrecking ball hit the futuristic GFRP home, it simply bounced off the structure. The fiberglass House of the Future had to be dismantled by hand. This fully highlighted the astonishing strength of fiber-reinforced polymer and its potential as a building material.
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In the 1950s , the construction and widespread implementation of the federal interstate highway system in the United States required year-round maintenance. During that time, the use of salt for ice removal on roads became prevalent, leading to the corrosion of metallic reinforcement in road and highway structures such as bridges, overpasses, viaducts, pipes, tunnels, and more. To address this issue, various protective coatings were explored, including polymer concretes, zinc coatings, epoxy coatings, electrostatically sprayed coatings, and fiberglass reinforcement. These research efforts aimed to find solutions that could provide durability and corrosion resistance in the harsh environments of road infrastructure
Among the options mentioned above, steel reinforcement with an epoxy coating emerged as the most effective solution. It became widely used in aggressive corrosion conditions. The use of composite reinforcement was not considered particularly efficient until the late 1970s due to the high cost of the reinforcement itself. It was only in 1983 when the U.S. Department of Transportation released the first project titled "Application of Composite Materials Technology in Bridge Design and Construction." It was discovered that fiberglass reinforcement was more effective than steel reinforcement for polymer concrete, due to the incompatible thermal expansion characteristics between steel and polymer concrete.
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In the late 1970s , the deteriorating condition of bridges due to corrosion became a concern for authorities in the United States. Corrosion caused by the detrimental effects of chloride ions leads to the rapid aging of bridges. The emergence of corrosion in epoxy-coated reinforcement sparked interest in alternative methods that could prevent it. Once again, composite reinforcement became regarded as the primary solution for addressing corrosion-related issues in bridges and other structures.
The significant demand for non-metallic, reinforcement emerged in the market during the 1980s, primarily for specific advanced technologies. Composite reinforcement, with its dielectric properties, began to be widely used in the construction of medical centers, particularly in rooms housing Magnetic Resonance Imaging (MRI) machines. It also found applications in breakwater structures, airport runways, foundations of electrical power station reactors, and electronic laboratories. The unique characteristics of composite reinforcement made it an attractive choice for these specialized applications.
In the USSR ,the first continuous technology for producing Ø 6 mm composite reinforcement was developed in the 1970s. At that time, the reinforcement was made from alkali-resistant glass fiber with a low-zirconium composition of the Shch-15ZhT grade. Its mechanical and physical properties were thoroughly studied and analyzed. The solid alkali-resistant glass fiber with a diameter of 10-15 microns was initially used as the load-bearing core in this reinforcement, and the fiber bundles were bonded together with synthetic resins to form a monolithic rod. The durability and chemical resistance of the glass fiber and reinforcement in concrete were carefully examined in various aggressive environments. Subsequently, it became possible to obtain GFRP reinforcement with the following characteristics:
  • Ultimate tensile strength: up to 1500 Mpa;
  • Initial modulus of elasticity: 50,000 Mpa;
  • Density (with a glass fiber content of 80% by weight): 1.8-2.0 t/m3;
  • Ultimate deformation: 2.5-3%;
  • Long-term strength of the reinforcement: 65% of the ultimate tensile strength;
  • Coefficient of linear expansion: 5.5-6.5 x 10-6.
Under the influence of static loads,the reinforcement was studied in initially stressed bending elements. Technological rules for the production of reinforcement were prepared, and design proposals for concrete structures with composite reinforcement were developed. Reasonable areas of their application were identified. These efforts aimed to establish guidelines and recommendations for the manufacturing and design of structures using composite reinforcement in order to ensure their proper and effective use.
The first operational section for experimentson a 10 kV power line with fiberglass-reinforced concrete crossarms was constructed in 1970 near Kostroma (USSR). The experimental section for a 35 kV power line with electrically insulating fiberglass-reinforced concrete crossarms was put into operation in 1972 in Stavropol (USSR). Two experimental sections for 10 kV power lines began operation in 1975 in the areas of Grodno and Soligorsk (USSR). Experimental support sections for 0.4 kV and 10 kV power lines, equipped with crossarms made of polymer concrete reinforced with Ø 6 mm fiberglass reinforcement, were put into operation in 1979 near Batumi (USSR).
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Near the cities of Rogachev and Cherven (USSR) in 1976, two movable warehouses were constructed. The inclined elements of the upper belt arches were reinforced with prestressed Ø 6mm fiberglass reinforcement. The use of reinforced load-bearing elements resulted in a 22% saving in wood, which contributed to a 9% reduction in construction costs. Additionally, the weight of the structure was reduced by 20%. The overall cost of the building, compared to similar warehouses of the same capacity, decreased by 1.7 times.
Fiberglass reinforcement was widely used in polymer concrete tanks in electrolysis workshops at non-ferrous metallurgical plants (Ust-Kamenogorsk, USSR). It was also employed in chemical industrial facilities, as well as in the foundation and flooring panels of mineral fertilizer warehouses. However, at that time, it was not possible to fully utilize fiberglass reinforcement on a large-scale factory production level.
In 1975 , the construction of the world's first glued timber bridge with a length of 9 meters was completed. The project was developed by the Department of Bridges and Tunnels at the Polytechnic Institute in Khabarovsk (USSR). The structure of the wooden bridge included fiberglass reinforcement rods for reinforcement. Another bridge of this type was constructed in the USSR in 1981, crossing the Shkotovka River in Primorsky Krai. In 1989, a bridge utilizing fiberglass reinforcement was built in the Khabarovsk Krai (USSR).
In Germany , in the early 1980s, fiberglass reinforcement began to be used for the reinforcement of concrete bridges. The two-span highway bridge with a width of 15 meters on Ulenbergstrasse in Düsseldorf, reinforced with fiberglass rods, was opened to traffic in 1987. After the completion of this bridge construction in Germany, programs were developed to research and utilize composite reinforcement. Thanks to the European BRITE/EURAM Project, which was titled "Fiber Reinforced Polymer Elements and the Application Technology of Non-Metallic Reinforcement," experiments and comprehensive material analysis of Fiber Reinforced Polymer (FRP) were conducted from 1991 to 1996. Later, the European research and demonstration project program was led by the company EUROCRETE.
In 1986 and 1988 , bridges were constructed in Japan using prestressed Carbon Fiber Reinforced Polymer (CFRP) reinforcement in their structures. This marked the beginning of using non-metallic reinforcement in the construction of marine ports. FRP reinforcement was widely utilized in Japan until the mid-1990s. At that time, the country had over 100 projects incorporating fiberglass reinforcement in their designs.
In 1997 , FRP rods were used in the deck construction of the Crowchild Bridge near Alberta, Canada. Canadian engineers developed guidelines for the use of FRP reinforcement in accordance with the Canadian Highway Bridge Design Code, which led to the design and construction of several demonstration projects. CFRP and GFRP reinforcement were used during the construction of the Headingley Bridge in Manitoba in 1997 and the Joffre Bridge in Sherbrooke in 1998. Additionally, in 1997, a bridge equipped with fiber optic sensors was opened. These sensors were integrated into the FRP reinforcement structure to remotely monitor deformations. Canada continues to be a leader in the application of fiberglass reinforcement in bridge deck construction to this day.
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In North America, there are currently two major manufacturers of composite reinforcement: Hughes Brothers (USA) and Pultrall (Thetford Mines, Canada). These companies are members of the Composite Rebar Manufacturers Council, supported by the American Composites Manufacturers Association. They actively contribute to the development of various requirements and standards for the use of composite reinforcement. One of the most well-known construction standards for the use of composite reinforcement is ACI 440R, "Guide for the Design and Construction of Concrete Reinforced with Fiber-Reinforced Polymer (FRP) Bars." Hughes Brothers' fiberglass reinforcement has been used in the construction of a concrete bridge in Morrison, Colorado. The bridge was built by the Colorado Department of Transportation and has a total length of 13.8 meters. During the construction of the bridge, fiberglass reinforcement was used in the piers, abutments, wing walls, parapets, and the curved monolithic concrete arch.
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The use of fiberglass reinforcement has become necessary in the construction of hospital rooms for magnetic resonance imaging. Port structures also rely on the use of composite reinforcement in their construction. Additionally, fiberglass reinforcement is widely used in the reinforcement of bridge decks, various precast concrete products, decorative and architectural concrete, and in tunnel construction.
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