Glass rebar refers to rebars that are made with glass fibers. These rebars are sold in the market as fiberglass rebar or GFRP for short, and these days it has found a special place in global markets. Glass fiber reinforced polymer (GFRP) is one of the approved methods in the construction of reinforced concrete. International construction standards have approved the use of these rebars for many Construction applications and there are specific rules and codes for their use. Glass rebar compounds consist of two main components. Fibers called glass fibers are used as reinforcing structures and epoxy resin or other reinforcement matrices that create the main substrate for these fibers to be put together. Epoxy resin matrix along with glass fibers creates a structure that in many materials, has the ability to compete with different types of steel rebars. Epoxy resin matrix along with glass fibers creates a structure that in many materials, has the ability to compete with different types of steel rebars.
What is Glass Rebar?
As mentioned, steel is not used in the manufacture of glass rebar and by putting the fibers together in suitable context, a strong structure is formed that is resistant to corrosion. EPOROD is able to produce composite rebars with glass fibers from 3 mm to 40 mm in diameter which is offered to the market in two different grades, Grade 1, yellow and completely non-conductive, Grade 2, Black and anti-UV but semiconductive.
Reinforced Concrete with Glass Rebar
Traditionally, reinforced concrete items consist of reinforced concrete the main structure of which is Portland Cement and steel rebar. The main function of concrete in this structure is to bear compressive loads and the tensile and shear loads are tolerated by steel bars embedded in the concrete. Such a structure is efficient where the main load is applied by pressure and the steel bears the partial tensile and shear load tolerance. . However, corrosion that threatens steel bars over time is one of the most important factors in the destruction of reinforced concrete. Corrosion reduces the stability of steel and reduces its lifespan, and solutions to this dilemma, which is usually accompanied by creating a coating for steel rebar, impose high costs on the project. These days, technology has found suitable alternative solutions to this problem.
GFRP glass rebar is a structure that is commercially available, and in addition to being a good substitute for steel, it does not cause the problem of corrosion either. Two main points are important in the examination of glass rebar. The first point is stability against corrosion and the second point is the long strain against failure which will give the manufacturer enough time to warn before failure.
Comparison of Performance in Glass and Steel Rebars
After production of reinforced concrete with glass rebar, the mechanical properties of reinforced concrete are usually tested with GFRP bars and compared with steel rebars. For testing usually concrete samples (unreinforced concrete, smooth GFRP reinforced concrete, gravel coated reinforced concrete and steel reinforced concrete) with a fixed ratio of ingredients (1:1.5:3) and the ratio of 0.5W/C in two periods of 7 and 28 days is considered at ambient temperature. The results of comparison of glass reinforcement and steel rebar in reinforced concrete are as follows:
- • Volume reduction with glass rebar and steel rebar in reinforced concrete (5% of the volume) distributed evenly in the mold.
- • The tensile strength of glass armature is 1200 MPa.
- • The flexural strength is 760 MPa.
- • Compressive strength in the expected range in concrete is 25.67 MPa.
- • The flexural strength of unreinforced concrete is 3 MPa and reinforced concrete with GFRP rebar, especially the flexural strength of sand-covered RC glass rebar is 13.5 MPa.
- • Therefore, glass rebar bonds more with concrete and has recorded a higher strain of 10.5 MPa in 28 days compared to steel reinforced concrete.
Price of Glass Rebar
The price of glass rebar is cheaper than steel rebar in the world markets. Reinforced concrete 4400 made with glass bars is sold for $6,400 worldwide, while reinforced concrete reinforced with steel costs about $600 to $3,300 more. In this estimation, the cost of covering concrete is also ignored. This is while reinforced concrete produced with steel is more prone to fatigue and cracking. That is why many manufacturers tend to use glass armatures in similar circumstances.
Advantages of Glass Rebar
Glass rebar as a polymer rebar reinforced with glass fibers has long been used as a replacement for glass. Light weight, corrosion resistant, excellent tensile strength and good mechanical performance are the characteristics of this rebar. Installation of composite rebar is similar to steel rebar and faces fewer transportation and maintenance problems.
Glass Rebar Compounds
What is known as matrix material can be considered as a substrate material. Matrix refers to integrated materials that are usually used to reinforce the structure and are distributed uniformly in the substrate. Materials such as aluminum, magnesium, nickel and cobalt can be used as matrix material. Various types of matrices are present in the market. The mechanical characteristics of polymers, including resistance and hardness, drop sharply with the rise in temperature, this critical temperature is known as glass transfer temperature (Tg), and the type of matrix or substrate is important because it is supposed to act as an inhibitor in the composite against factors such as corrosion, electrical and thermal resistance.
Glass Rebar Substrate Material
Known matrices include polyester, vinyl ester, phenol and epoxy. In what follows, types of glass rebar substrate matrices are investigated:
- • Vinyl ester as a subgroup of unsaturated polyester exhibits excellent resistance to corrosion. In alkaline environments such as concrete, the use of this matrix is more common such that it is used in FRP rebar production along with epoxy matrix.
- • Polyester is known as the most widely used matrix since it leads to production of composite with unique characteristics. The point is that polyester matrix does not work well in alkaline environment, so if used as FRP rebar substrate, it should not be expected to resist alkaline environments. Also, this matrix has good resistance against impact and fatigue.
- • Epoxy is the best and most commonly used matrix for carbon fiberglass composites. Composite made with epoxy matrix has significant advantages in terms of mechanical properties and fatigue resistance. Epoxy also has good resistance against heat and can be expected to withstand about 160 degrees of heat. In concrete there is up to 320 degrees fire resistance.
- • Phenol is used where high fire resistance is expected. Among the remarkable properties of phenol is high thermal resistance, less smoke production, and prevention of spread of fire in contact with fire.
Epoxy Resin Suitable Rebar for Marine Structures
Epoxy resins used in FRP composite rebar production are highly resistant to chemicals such as acid, salt and water and prevent corrosion of rebars. Considering the high strength of these rebars, it is the best choice for structures that are exposed to moisture and especially salty water. The bridge decks, docks and most offshore structures show better stability of parts with these rebars.