GFRP rebar, whose name is shortened from glass fiber reinforced polymer, is a kind of composite material for strengthening structural elements. Today, the use of GFRP rebar or glass ribbed rebar is known as one of the newest methods of strengthening buildings and materials such as concrete.
In fact, this technology has covered many weak points of rebar and because of its many practical characteristics, it has entered various sectors of the industry. In this article, we discuss the issue of reinforcement using GFRP rebars.
What are the main components of GFRP rebar?
GFRP rebars are a family of FRP materials that use fiberglass in their construction. This material is manufactured by placing highly efficient glass fibers in a polymer resin layer and is used as concrete reinforcement in concrete structures.
Glass fibers are extremely thin strands of glass, of infinite length, about 5 to 25 microns in diameter. Generally speaking, we have 4 types of fiberglass, namely electrostatic glass, structural glass, chemical glass and alkaline resistant glass. Electric fiberglass is more widely used than other types due to its cheap price and high tensile strength.
The matrix type in these rebars is usually polyester resin and vinyl ester. Due to their favorable mechanical properties, these glass fiber reinforced polymers are known as an effective alternative to steel-reinforced concrete. Short cooking time, low price and large volume change during cooking are the characteristics of polyester resin.
In contrast, vinyl ester resin is more flexible and rigid. This resin performs better than polyester resins in terms of stability, abrasion resistance, impact resistance, and fatigue resistance.
GFRP rebar, whose name is shortened from glass fiber reinforced polymer, is a kind of composite material for strengthening structural elements. Today, the use of GFRP rebar or glass ribbed rebar is known as one of the newest methods of strengthening buildings and materials such as concrete.
In fact, this technology has covered many weak points of rebar and because of its many practical characteristics, it has entered various sectors of the industry. In this article, we discuss the issue of reinforcement using GFRP rebars.
What are the main components of GFRP rebar?
GFRP rebars are a family of FRP materials that use fiberglass in their construction. This material is manufactured by placing highly efficient glass fibers in a polymer resin layer and is used as concrete reinforcement in concrete structures.
Glass fibers are extremely thin strands of glass, of infinite length, about 5 to 25 microns in diameter. Generally speaking, we have 4 types of fiberglass, namely electrostatic glass, structural glass, chemical glass and alkaline resistant glass. Electric fiberglass is more widely used than other types due to its cheap price and high tensile strength.
The matrix type in these rebars is usually polyester resin and vinyl ester. Due to their favorable mechanical properties, these glass fiber reinforced polymers are known as an effective alternative to steel-reinforced concrete. Short cooking time, low price and large volume change during cooking are the characteristics of polyester resin.
In contrast, vinyl ester resin is more flexible and rigid. This resin works better than polyester resins in terms of use for GFRP rebars.
In GFRP rebars, glass is used, which is an insulating material and has great stability in different environments. For this reason, unlike steel, this material does not corrode, and in humid environments and structures exposed to chlorides, it is a suitable choice for strengthening concrete.
This feature has made composite glass rebars for use in situations such as construction of bridge decks, salt storage equipment, canals, marine ponds and structures, desalination equipment, sewage drains, etc.
Also, in cases where the concrete cover is insufficient for any reason, the possibility of steel corrosion is high and it is better to use glass rebar. GFRP rebars are effective in reducing the weight of the structure due to their lightness and high strength. This problem causes seismic strengthening of the building.
In cases such as insufficient bending and shearing of the reinforcement, insufficient size of the reinforcement, short length of the reinforcement, the need to create new openings in the slab, deterioration and corrosion, all factors that reduce the strength of the structure, use glass reinforcement to provide the necessary strength they take.
Another use of GFRP rebar is in concrete members exposed to high voltage and electromagnetic fields. Places such as railways, subways, hospital environments, MRI rooms, high-voltage power stations, aluminum and steel plants, radio stations, etc. include this category.
These rebars are a good alternative to galvanized and epoxy-coated steel. Construction of various processing plant units, concrete channels and pipes, precast concrete blocks, piles, manual tunneling, retaining walls and soil nailing, strengthening of structures and restoration of ancient monuments, etc., are other areas in which GFRP rebars can be used. .
The use of fiberglass reinforcement at the intersection of building materials without changing the shape of the structure increases its resistance and strengthens it against earthquakes.
Pat, abrasion resistance, shock resistance and fatigue resistance.
What are the advantages of strengthening with GFRP rebar?
The use of GFRP rebar is considered one of the effective solutions in strengthening and improving structures. The advantages of this method are as follows:
The tensile strength of GFRP rebar is relatively high and is about 3 times that of steel. Therefore, it can compensate for concrete’s weakness in tension better than steel.
Reinforced GFRP are electrical and thermal insulators, and their use increases the durability of structural elements against corrosion and damage.
The density of this rebar, with the desired resistance, is less than that of steel, and its use reduces the wear load of the structure.
Considering the high price of steel rebar, the use of fiberglass reinforcement greatly reduces the cost of projects and is economical.
Due to an 8-fold reduction in weight of GFRP rebars compared to
With steel rebar, costs related to implementation and transportation are reduced.
Fiberglass rebar is easier to cut and is performed more quickly and easily
Due to the relative flexibility of these small diameter rebars, they can be collected into a ring shape and stored in small spaces.
GFRP rebar adheres to concrete better than steel, and this will reduce the length of the patch.
Since these hardeners are corrosion resistant, the thickness of the concrete cover can be reduced. As a result, the thickness of surfaces and other parts and in general the volume of concrete consumed is reduced.
What are the disadvantages of strengthening using GFRP rebar?
Although strengthening buildings using GFRP rebars has many advantages, the performance of these reinforcements is still under investigation and studies in this field do not have a long history. In this section, some disadvantages of reinforcement using GFRP rebars are listed
Bending these types of rebar has more considerations than steel and is more difficult.
The property of sudden brittleness and brittleness at high tensions (unlike steel which acts ductile and flows first.)
Weakness against direct fire. (The concrete cover partially compensates for this weakness.
conclusion
Due to the extreme sensitivity of steel to corrosion, reinforcement with GFRP rebar in extreme environmental conditions is extremely important. We know so far the appropriate resistance, insulation and stability of this type of reinforcement, and despite the design regulations and special tests that researchers have taken into account for this type of reinforcement, reliable results have been obtained from their performance.
Of course, the necessary designs in large projects should be made by experienced engineers and the production process and brittle performance of these materials should be further investigated so that the benefits of strengthening with GFRP rebars can be enjoyed more reliably.