GFRP rebars Technology Deep Dive

Composite reinforcement, as a worthy alternative to traditional metallic reinforcement, started to be discussed as early as the 1970s. Glass Fiber Reinforced Polymer (GFRP) rebars are gradually replacing the familiar metal rebars. This construction material is actively used in developed countries around the world. The leaders in the use of non-metallic reinforcement are the United States, Japan, and China, with shares of 40%, 35%, and 30% respectively. GFRP rebars has a number of key features, which we will discuss below.

GFRP rebars: features

Unlike traditional steel rebars, GFRP rebars are made using a process called pultrusion. This involves pulling continuous glass fibers through a resin bath, followed by a heated die to create a solid, durable composite material. The cross-sectional design of GFRP rebars contributes to their strength. The fibers are evenly distributed throughout the composite, providing enhanced tensile strength. Additionally, the resin matrix surrounding the fibers provides protection against microcracks and prevents the propagation of cracks, increasing the overall durability of the material.

GFRP rebars exhibits high tensile strength, being 2-3 times stronger than its steel counterparts. It is lightweight, weighing 4-6 times less than steel rebars. It is not susceptible to corrosion, resistant to both saltwater and freshwater, and has a high elasticity modulus. The composite material is a dielectric, unaffected by electromagnetic fields, and is chemically inert. GFRP rebars has a guaranteed service life of 100 years. Another key advantage is its lower cost compared to steel rebars, as well as the ability to manufacture rebars of almost any length.

Areas of use

GFRP rebars is used in various areas of construction, including:

• Road and civil construction (it is used in the construction of bridges and airports);
• Reinforcement of all types of foundation;
• Reinforcement of concrete structures - it is used in concrete structures, even in environments that are aggressive to metals;
• Strengthening of various types of concrete - it is used in concrete that utilizes chloride and mineral additives;
• Construction of agricultural facilities - it is used due to the absence of emissions that are harmful to animals;
• Reinforcement and restoration of partially damaged or destroyed brick structures;
• Formation of water channels, sewage systems, and drainage systems;
• Construction of swimming pools;
• Reinforcement of riverbanks and construction of ports and coastal structures.

If you want to learn more about how to use of GFRP rebars, then go to the Applications page

FRP Standards and Regulations

FRP (Fiber Reinforced Polymer) standards and regulations are guidelines and specifications that define the requirements for the design, testing, manufacturing, and installation of composite materials in various applications. These standards ensure the quality, performance, and safety of FRP products. Here are some well-known FRP standards:

International

• ASTM D7205: "Standard Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite Bars";
• ISO 10406: "Fibre-reinforced polymer (FRP) composite bars — Specification".

USA

• ACI 440.1R (2015) "Guide for the Design and Construction of Structural Concrete Reinforced with FRP Bars";
• ACI 440.3R-04 (2004) "Guide for Test Methods for Fiber Reinforced Polymers (FRP) for Reinforcing and Strengthening Concrete Structures";
• ACI 440.5-08 (2008) "Specification for Construction with Fiber-Reinforced Polymer Reinforcing Bar";
• ACI 440.6-08 (2008) "Specification for Carbon and Glass Fiber-Reinforced Polymer Bar Materials for Concrete".

Canada

• CAN/CSA-S806-10, “Design and Construction of Building Components with Fibre-Reinforced Polymers";
• CAN/CSA-S6-06, "Canadian Highway Bridge Design Code";
• CAN/CSA-S807-10 "Specification for fiber-reinforced polymers";
• Design Manual No. 3, "Reinforcing Concrete Structures with Fiber Reinforced Polymers";
• Design Manual No. 4, "FRP Rehabilitation of Reinforced Concrete Structures";
• Design Manual No. 5, "Prestressing Concrete Structures with FRPs";
• Design Guide, "Specifications for FRP Product Certification".

Japan

Japan Society of Civil Engineers (JSCE) 1997 "Recommendation for Design and Construction of Concrete Structures Using Continuous Fiber Reinforced Materials".

Europe

• FIB Bulletin #10: "Bond of reinforcement in concrete"
• FIB Bulletin #40: "FRP reinforcement in RC structures"
• Report #STF 22 A 98741 "Eurocrete Modifications to NS3473 When Using FRP Reinforcement" Norway (1998)
• AASHTO LRFD : "Bridge Design Guide Specifications for GFRP-Reinforced Concrete Bridge Decks and Traffic Railings". 1st Edition in 2009.

Italy

CNR-DT 203/2006 - "Guide for the Design and Construction of Concrete Structures Reinforced with Fiber-Reinforced Polymer Bars".

In summary, GFRP rebars are a technological advancement in reinforcement materials. They are made through pultrusion, offer excellent corrosion resistance, and have a strong cross-sectional design. Compared to steel rebars, GFRP rebars are lighter, non-conductive, and possess high tensile strength. These features make GFRP rebars a reliable alternative for reinforcing structures, reducing the risk of corrosion-related issues and improving overall construction durability.