Composite rebar is a fairly young material that has become available on the construction market not so long ago. However, due to its many advantages, it has gained wide popularity. Many manufacturers claim that such products are capable of completely replacing steel reinforcement. However, its application is not always justified. It is worth taking a closer look at both the advantages and disadvantages of a composite. This will allow you to choose a material that will last for many decades.

Composite reinforcement is a rod made of fiberglass. A carbon fiber thread is wrapped around it. Due to its use, not only the strength of the product is ensured, but also reliable adhesion to concrete. Such products have both a number of advantages and certain disadvantages. For this reason, it is not always possible to use it.

Fastening of carbon fiber rods is carried out with special clamps. There is no need to use welding for bonding. This is its significant advantage.

For each situation, it is worth considering the features of the use of such products. The application of this approach will ensure the reliability and efficiency of fastening various structures.

With insufficient consideration of the characteristics of the product and without comparing them with metal reinforcement, it is possible to significantly harm the building structure if composite materials are used. For this reason, even before using composite products, it is worth finding out in which cases their use will be appropriate.

Important! It is also worth paying attention to the physical and mechanical properties of composite products.

Main advantages

Composite reinforcement has a number of positive qualities. Among its main advantages are:

Also, the material has many disadvantages, which should be considered in more detail.

Main disadvantages

Before purchasing fiberglass reinforcement, you should learn about all its characteristics, as well as about the main disadvantages. The disadvantages of the material include:

• She does not tolerate high temperatures. However, it is quite difficult to imagine a case in which it can heat up to 200 degrees inside a concrete structure.
• High price. However, this disadvantage is overridden by the possibility of using CFRP products of a smaller diameter than metal products.
• Composite reinforcement has poor bendability. This property imposes certain restrictions on its use to strengthen a concrete structure. However, bent sections can also be reinforced with steel rods.
• Such products do not cope well with fracture loads. This circumstance is critical for most concrete structures.
• Compared to metal reinforcement, fiberglass products are less rigid. This disadvantage does not allow to transfer large vibration loads that appear when pouring concrete using a car mixer. When this technique is used, the concrete structure is subjected to heavy loads. In this regard, design defects are possible.

If we consider the disadvantages of carbon fiber reinforcement, we cannot say about the absolute advantage of one material over another. In any case, when choosing composite products, you should be careful, take into account its pros and cons, as well as the conditions of use in a particular situation.

Important! Since the composite material does not have sufficient flexural strength, it is not suitable for knitting when laying steel rods. For this, it is better to use plastic clamps.

Applications

The armature, which is made of various composites, has found application in both private and capital construction. The rules for its installation can be studied independently according to the manufacturer's instructions. Since there is no point in using composite products in capital construction, it is worth focusing on the construction of concrete foundations for private houses.

The main areas of use of fiberglass products:

To summarize the above, it is worth noting that fiberglass reinforcement can be effectively used in most cases. However, it is worth considering the shortcomings of the material and the associated operating restrictions. They are often specified by the manufacturer.

Important! Composite reinforcement is knitted using plastic clamps.

Can fiberglass reinforcement replace metal

Fiberglass products have appeared on the construction market relatively recently. However, a lot of videos and text materials have been created on the topic of its use. Considering the above recommendations, it can be argued that fiberglass products can be used when strengthening walls or for connecting load-bearing structures with partitions.

The main advantage of fiberglass reinforcement is that it does not rust. In addition, when using it, cold bridges do not appear, which cannot be said about metal rods. The use of such material is justified in cases where the building being constructed will not be too heavy. It is also necessary to use it only when building a house on stable ground.

Long-term practice has not yet confirmed the success of this material. There are not enough reviews about him yet to draw a correct conclusion. For this reason, every developer in a certain sense takes risks using composite rebar. If you plan to erect a structure to which high requirements for strength and stability are imposed, you should choose metal reinforcement.

conclusions

When choosing composite reinforcement for reinforcing concrete structures, it is worth considering its main pros and cons. So, the material is lightweight, easy to transport and fairly good strength indicators. However, it cannot withstand high fracture loads. For this reason, traditional metal bars should be chosen for buildings with high demands in terms of strength and stability.

Such a composite consists of a fiberglass cord wrapped with a carbon fiber thread. Due to the use of the latter, adhesion to concrete is increased. If you plan to build a lightweight structure, you can use a composite. Typically, composite reinforcement is used in the construction of low-rise buildings. Fiberglass reinforcement is used for both tape and slab bases.

When using fiberglass, it is better to consult with experienced builders. It is especially important to enlist their help when drawing up a construction project.

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Which appeared on the construction market relatively recently, has both advantages and disadvantages, which the consumer must be aware of. Despite the assurances of manufacturers that this product is a full-fledged replacement for metal fittings, not in all situations its use can be considered justified.

What is fiberglass reinforcement

The so-called composite reinforcement is a fiberglass rod, around which a carbon fiber thread is wound, which serves not only to strengthen the structure of such a product, but also to ensure its reliable adhesion to concrete mortar. The fittings of this type have both pros and cons, and their use should be approached very carefully.

Plastic clamps serve as elements for fixing the carbon fiber reinforcing bars. It is convenient that welding is not required to connect the elements of such reinforcement, which is undoubtedly a big plus.

When assessing the feasibility of using fiberglass reinforcement, it is necessary to consider all the pros and cons of its use in certain situations. This approach will ensure the high efficiency of this material as a means of strengthening building structures for various purposes.

If you do not take into account the characteristics of fiberglass reinforcement and do not compare them with the parameters of similar products made of metal, you can seriously harm the future building structure or finishing elements. That is why, before proceeding with the selection of elements for reinforcing concrete structures, you should figure out in which cases the use of certain products is more appropriate.

Main advantages

Among the advantages that distinguish carbon fiber reinforcement are the following.

• An important advantage of fiberglass reinforcement is its low specific weight, which makes it possible to use it for reinforcing lightweight structures made of aerated concrete and some other building materials. This allows you to significantly reduce the weight of structures that are reinforced with it. Meanwhile, the weight of a conventional concrete structure when using fiberglass reinforcement will decrease slightly, since the building material itself has an impressive mass.
• Low thermal conductivity is also one of the advantages of fiberglass reinforcement. When using such reinforcement in concrete structures, cold bridges are not formed (which cannot be said about reinforcing metal elements), which significantly improves their thermal insulation parameters.
• The high flexibility of fiberglass reinforcement allows it to be shipped to the customer in coils, and not cut into separate rods. Due to the compact form of packaging, it is much easier to transport such fittings, for which you can use the trunk of any car, and this seriously reduces the cost of delivering material to the place of construction work. The use of reinforcing elements that are shipped not in cut rods, but in coils, also allows you to reduce material costs by reducing the number of overlaps. This positively affects both the strength characteristics of the future concrete structure and its cost, which is especially important when performing construction work.
• Such an advantage of fiberglass reinforcement as its durability inside a concrete structure is considered quite controversial. Metal fittings, being in an insulated state, are also not exposed to the negative influence of external factors, which ensures the durability of its use.
• CFRP is a dielectric material, which is the advantage of products made from this material. Electrically conductive metal fittings are more susceptible to corrosion, which negatively affects their durability.
• Compared to metal reinforcing elements, fiberglass products are not exposed to chemically active media. Such an advantage of fiberglass reinforcement is especially important in cases of construction of buildings in winter, when various salt solutions are added to concrete, which accelerate the hardening process.
• As a dielectric, CFRP does not generate radio interference inside a building, unlike metal rods. This advantage is important when there are many reinforcing elements in the concrete structure. Otherwise, the use of composite reinforcement will not be a disadvantage, but it will not be so relevant.

Fiberglass reinforcement also has disadvantages, which should also be known to potential consumers.

Main disadvantages

The disadvantages of fiberglass reinforcement are associated with the following characteristics.

• The disadvantages of fiberglass reinforcement include, in particular, the fact that it does not withstand exposure to high temperatures. At the same time, it is difficult to imagine a situation where a reinforcing cage inside concrete can be heated to a temperature of 200 degrees.
• A rather high cost is a conditional disadvantage, given the fact that fiberglass reinforcement of a smaller diameter can be used to reinforce concrete structures in comparison with metal products.
• Carbon fiber reinforcement bends poorly. This disadvantage limits its use when creating reinforcing frames for concrete structures. Meanwhile, it is possible to make bent sections of the reinforcing cage from steel elements, and then build them up using fiberglass rods.
• Reinforcement made of fiberglass does not withstand fracture loads poorly, which is very critical for concrete structures. Accordingly, their reinforcing frame must successfully withstand such loads, which the reinforcement made of composite materials cannot boast of.
• In contrast to the metal reinforcement cage, fiberglass products have less rigidity. Because of this drawback, they do not tolerate vibrational loads that arise when they are poured with a car mixer. When using this technique, the reinforcement cage is exposed to significant mechanical loads that can cause its breakdown and disruption of the spatial position of its elements, therefore, rather high requirements are imposed on the rigidity of such concrete structures.

Considering the advantages and disadvantages of fiberglass reinforcement, it is difficult to say how much better or worse it is than made of metal. In any case, the choice of this material should be approached very reasonably, using it to solve the problems for which it is really intended.

Fields of application of fiberglass reinforcement

Reinforcement made of composite materials, the installation rules of which are easy to learn from the corresponding videos, are used in both capital and private construction. Since capital construction is carried out by qualified specialists who are well familiar with the nuances and disadvantages of using certain building materials, we will dwell on the features of using such material in the construction of private low-rise buildings.

• Reinforcement made of composite materials is successfully used to strengthen the following types of foundation structures: strip, the height of which is greater than the depth of soil freezing, and slab. The use of CFRP reinforcement for strengthening foundations is advisable only in cases where the structure is being erected on good soil, where the concrete foundations will not be subjected to fracture loads, which fiberglass elements may simply not withstand.
• With the help of fiberglass reinforcement, walls are strengthened, the masonry of which is made of bricks, gas silicate and other blocks. It should be noted that as a connecting element of walls, composite reinforcement is very popular among private developers, who use it not only to strengthen the masonry of load-bearing structures, but also to ensure their connection with facing partitions.
• This material is also actively used to bond the elements of multilayer panels. The structure of the latter includes a layer of insulation and concrete elements, which are connected to each other using fiberglass reinforcement.
• Due to the fact that the reinforcement of this type is devoid of such a disadvantage as susceptibility to corrosion, it is often used to strengthen various hydraulic structures (for example, dams and basins).
• In cases where it is necessary to effectively increase the rigidity of glued timber beams, they are also reinforced with fiberglass reinforcement.
• This material is also used in road construction: with its help, the layer of asphalt road is strengthened, which is subjected to increased loads during its operation.

Summarizing all of the above, it should be noted that the use of fiberglass reinforcement can be quite effective, if we take into account its disadvantages and the associated limitations, which are negotiated by the manufacturer.

Is fiberglass reinforcement able to replace metal counterparts?

Despite the fact that reinforcement made of composite materials is a fairly new material on the construction market, you can already find many recommendations (and even videos) on its use. Taking into account these recommendations, we can conclude that it is best to use fiberglass reinforcement for strengthening walls erected from bricks and building blocks, as well as for connecting load-bearing walls with interior partitions.

Modern building technologies provide for the use of new materials with improved characteristics. One of the latest developments of scientific and construction organizations is plastic fittings. Due to its complex of operational properties, it successfully competes with metal rods, which are gradually destroyed as a result of corrosion processes. Glass reinforcement is used to provide an increased margin of safety for concrete structures in contact with fresh and salt water, as well as aggressive media.

Composite rebar - fiberglass material for concrete reinforcement

Composite fiberglass rebar is a new building material made from various fibers:

• basalt;
• glass;
• polyamide;
• carbon fiber.

Fiberglass reinforcement is a building material created on the basis of fibers connected by a complex composition

The name of the polymer reinforcement is determined by the type of fibers used:

• basalt-plastic rods are made from basalt thread;
• fiberglass reinforcement is made on the basis of glass fiber.

Novice developers are interested in whether it is possible to use fiberglass reinforcement for the foundation, as well as how fiberglass reinforcement behaves in aerated concrete walls. Modern manufacturing technology, which provides for the impregnation of a fiber bundle with a thermoplastic mixture based on polymer components, provides the required strength of the finished product.

Polymerizing at an elevated temperature, the threads collected in a bundle freeze and acquire the required shape. The combination of fiber yarns improves performance.

Improved adhesion of glass reinforcement to concrete is provided by applying the following materials to the outer surface of polymer rods:

• fine sand;
• marble particles;
• crushed granite.

Transverse or spiral corrugations increase the strength of the reinforcement and improve adhesion to the concrete mass.

Fibers are bonded together by polyester resin composite

Plastic fittings - features of building materials

Plastic reinforcement designed to increase the strength of a concrete structure has its own characteristics.

The main difference between this material is light weight, as well as a two-layer construction:

• the inner layer is the core of the bar, which consists of longitudinal threads embedded in a composite mixture. The core increases the resistance of the material to the effects of bursting and compressive loads;
• the outer layer is formed by a group of threads twisted in a spiral. The characteristic arrangement of the outer fibers increases the torsion resistance of the bars and also improves the contact of the polymer reinforcement with concrete.

Polymer filaments enhance the performance of composite rods that compete successfully with standard metal reinforcement. Distinctive features of glass fittings:

• 4-5 times lower weight compared to steel rods. The main advantage of the material makes it easier to work and reduce transportation costs;
• the tensile strength of the polymer material is twice that of steel. This makes it possible to provide the required margin of safety with reduced parameters of the outer diameter;
• resistance to corrosive destruction and neutrality to aggressive liquids. Polymer rods retain their properties in a humid environment;
• reduced thermal conductivity coefficient in comparison with steel. Polymer material allows for the construction and repair of houses, preventing the formation of cold bridges;
• the possibility of assembling power frames without electric welding. This simplifies the bar clamping process and also reduces costs.

Fiberglass is used for the production of these building fittings.

Design features and performance characteristics allow the use of glass reinforcement instead of steel bars to solve a wide range of tasks.

Glass reinforcement - types of rods

Plastic fittings are made from different types of threads. The following types of composite rods are used:

• fiberglass, abbreviated as ASP. The core is made of glass fibers that are highly resistant to moisture. Products are used to increase the strength of foundations and road surfaces;
• basalt-plastic, labeled with ABP. They are easily distinguished by the black color of basalt fibers. Basalt rods are superior to fiberglass rods in their ability to take tensile loads, as well as in the amount of elastic deformation;
• Carbon fiber rods with UGP marking are made on the basis of carbon used in the production of concrete composites. The increased level of costs for the purchase of carbon fiber reinforcement is compensated by the working properties of the material, as well as the ease of working with it;
• combined. The armature with the ACC index is made of basalt and glass fibers, characterized by increased strength properties. ACC polymer rods on a glass-basalt base are used for special purposes.

The choice of composite rods is carried out depending on the complexity of the tasks.

There are various variations of the valve model, some of which are quite unusual.

How are plastic fittings made?

The production process of polymer reinforcement is carried out on automated lines and includes the following stages:

1. Filling the hopper of the feeding module with a polymer composition.
2. Feeding composite fibers and ensuring uniform tension.
3. Heat treatment of the material to remove water and oil inclusions.
4. Loading polymer fibers into a tank with heated binding ingredients.
5. Pulling the impregnated filaments through a nozzle that winds them.
6. Polymerization of the starting material in an oven at a high temperature.
7. Cooling of the resulting rods and cutting them into billets of the required dimensions.

The characteristics of the equipment guarantee the quality of the products obtained.

Scope of glass reinforcement

Polymer fittings are used to solve various problems:

• production of composite concrete used for the construction of monolithic structures;
• construction of building foundations and pouring monolithic slabs;
• increasing the strength of walls built of bricks;

The scope of application of this building material is extensive.

• construction of port facilities and special structures to strengthen the coastline;
• construction of road pavements and reinforcement of concrete slopes;
• construction of protective structures for railway and transport highways;
• production of concrete products in need of prestressed;
• construction of road junctions, bridges, overpasses and flyovers;
• construction of concrete structures in seismic zones.

Plastic rods do not need a waterproofing device, regardless of the choice of the structure reinforcement scheme. The use of fiberglass reinforcement for concrete reinforcement and the use of polymer rods are based on preliminary calculations. The technique of calculating reinforced concrete for construction is owned by employees of specialized organizations.

Advantages of glass fittings

Developers are interested in the pros and cons of plastic fittings. Like all building materials, fiberglass reinforcement has advantages and disadvantages. The main advantages of glass fittings:

• increased safety margin;
• acceptable price level;
• low weight of rods;
• corrosion resistance;
• resistance to aggressive environments;
• reduced thermal conductivity;

Today, plastic fittings are used more and more in construction due to their unique characteristics.

• ecological cleanliness;
• long period of operation;
• ease of machining;
• convenient delivery option;
• the possibility of assembling frames without the use of welding;
• preservation of properties at low temperatures;
• dielectric characteristics.

Due to the complex of advantages, composite rods are popular.

Weaknesses of fiberglass rods

Along with the advantages, glass reinforcement also has disadvantages.

Main disadvantages:

• decrease in strength properties when heated over 200 ° C;
• increased likelihood of fire when heated;
• insufficiently high modulus of elasticity;
• decrease in strength properties during operation and contact with alkalis;
• impossibility of bending bars without the use of special technological methods.

These disadvantages limit the scope of use.

The modern world is changing rapidly, and this also applies to the construction sector - new technologies and materials. Today, the use of composite reinforcement in construction is not widespread, and the main reason for this is the lack of information and real, independent reviews from builders. After all, it is much more habitual and more reliable to use old, good metal fittings, the characteristics of which are well known and confirmed by time.

But reinforcement made of composite materials has been used in Western countries since the 70s, and received quite a high rating. Although there she was unable to squeeze out the steel.

In our country, many people still ask: what is fiberglass reinforcement? And they receive a lot of information - both fantastically laudatory (as a rule, coming from the manufacturers of plastic fittings themselves), and very negative (manufacturers of steel fittings do not need competitors either). We will try to calmly and impartially analyze the advantages and disadvantages of composite reinforcement.

How are composite rebar made?

Let's start with the fact that the term "composite reinforcement" unites all types of non-metallic reinforcement, produced on the basis of different types of fibers, which are used as the reinforcing base of the rod. The fibers from which the reinforcement is made can be as follows:

• 1. basalt fiber;
• 2. glass fiber;
• 3. aramid fiber.
• 4. carbon fiber.

Thus, the types of composite reinforcement, depending on the applicable fibers, are as follows:

• 1. Basalt plastic reinforcement, usually black (ABP);

• 2. Fiberglass reinforcement, light yellow, however, thanks to the coloring additives, the color gamut is wide (ASP);

• 5. Combined reinforcement (based on different types of fibers).

Any composite reinforcement is produced on the same equipment, the technology does not differ either. The only difference is in the type of fibers. Currently, there are several production methods:

1. A bundle of fibers, having previously formed a bar - the main rod of the reinforcement, is impregnated with epoxy resin and pulled out. Then the bundle of fibers is pulled by the shafts, while winding around it a tourniquet made of the same fibers using resins. The rope in this process performs two tasks - it tightly presses the fibers of the rod, and serves as reinforcement ribs, which will improve the adhesion of reinforcement and concrete in the future. After that, the fittings undergo a drying stage in the oven, and now, the fittings are ready. This method is the oldest, almost all Russian manufacturers of plastic fittings use it.

1.Fiber feeding system (fiberglass, carbon fiber, basalt fiber)

2.Polymer bath (polyester, epoxy resins)

3. Preforming device

4.Filiere

5.Zones of heating / cooling of the die

6.Pulling machine

7.Cutting machine

2. The second method differs from the first only in that the rope is wound onto the rod with a very strong force, it is literally pressed into the main rod, as a result of which the ribs are formed from the fibers of the rod itself. Such reinforcement is more durable than the one produced by the first method, since there is no risk of ribs falling off. However, it is almost impossible to find such Russian-made fittings, since most of them use the first method.

3. The third method is also similar to the first one, however, the tightening rope does not form ribs here, but only tightens the fibers of the bar until the moment of polymerization in the oven. For adhesion to concrete, a layer of abrasive is applied to the reinforcement - quartz sand. This type of reinforcement has the worst adhesion to concrete, and, moreover, the shortest service life. The fact is that epoxy resin quickly decomposes in an alkaline environment of concrete, and polyester resins, which are not afraid of alkali, are extremely rarely used by manufacturers in Russia.

4. Finally, pultruded reinforcement. In this case, the fibers are formed into a rod, impregnated with polymer resins, and pulled through dies with different sections, located in descending order. This method allows the formation of periodic relief (ribs) with high accuracy, so that they can be used as a thread (for example, as a tightening screw for formwork, with a fiberglass or steel nut). The fittings produced in this way are of high quality, durability and high price. In addition, such fittings are almost never produced in Russia.

If you search, you can find on sale a completely unusual material - composite reinforcement with an internal cavity. Despite its exoticism, the tube reinforcement deserves attention - after all, thanks to the cavity, the diameter increases, and with the same number of fibers, the reinforcement with the cavity has a larger area of ​​contact with concrete, which means better adhesion.

Composite rebar pros and cons

Like any building material, composite reinforcement has its own advantages and disadvantages. Pros of composite reinforcement:

1. Weight - non-metallic reinforcement is practically a feather, in comparison with metal one. The weight of composite reinforcement is 10-12 times less than that of steel equal in strength. For example, 1 meter of plastic reinforcement 10 mm weighs 100 grams, and steel of the same diameter - 617 grams. And the fact that the plastic rolls into the bays allows you to immerse several bays (the length of the bay is usually 100-200 meters) of the fittings into the trunk of a car.

2. Composite reinforcement has an impressive tensile strength - 2.5-3 times higher than that of steel (of course, with the same diameter). Thus, composite reinforcement with a diameter of 12 mm replaces steel with a diameter of 14-16 mm. Hence the term "equal strength replacement" is used by builders and manufacturers.

3. The cost of composite reinforcement today is lower than for metal, although a few years ago it was the other way around. Moreover, the price of steel reinforcement is steadily growing, while the composite one remains almost in place.

4. Another plus - composite rebar is sold in coils of 100-200 meters, which can significantly reduce the amount of scrap when reinforcing structures.

But not everything is so cloudless, there are also disadvantages of composite reinforcement:

1. The main disadvantage of composite reinforcement experts call the low modulus of elasticity, 4 times lower than that of steel - and this is with the same diameter. Of course, this is not a critical drawback, the main thing is to make additional calculations, and it is better if specialists do it. Or our calculator.

2. It is possible to bend composite reinforcement only in production; it will not be possible to bend it at an angle at the construction site. True, elements in the form of rods at an angle are usually required a little, besides, they can be replaced with steel reinforcement.

3. Fiberglass reinforcement does not withstand high temperatures - at 100 degrees it ceases to be elastic and easily breaks.

4. Welding when using composite reinforcement is unacceptable, although some experts consider it an advantage. Indeed, when reinforcing with steel or plastic reinforcement, both are mainly knitted with wire or plastic ties.

There is an erroneous statement that it is possible to knit composite reinforcement only with plastic ties (clamps). Of course it is not. Moreover, we recommend knitting with regular annealed steel knitting wire. The process of tying composite reinforcement is no different from tying metal reinforcement. And the goal is one - to fix the frame until the concrete is hardened, then it does not matter at all what and how the fiberglass reinforcement was knitted.

By the way, it is necessary to say a few words about the cutting of composite rebar. Not everyone knows that it is possible to cut, bite or saw through fiberglass reinforcement, but not at all. The best option to cut the composite is with a grinder. The fact is that biting or chopping creates microcracks, which, although not visible to the naked eye, go deep into the core. Water and alkali get into the cracks, and during freezing and defrosting, the cracks will expand, gradually destroying the reinforcement.

Important! When cutting composite reinforcement, the necessary safety measures should be taken - to protect the eyes and respiratory organs, since fine dust from basalt or glass fibers is extremely harmful.

Where is fiberglass reinforcement used?

The use of composite reinforcement in construction is quite wide, although not very widespread in Russia. It is mainly used in the construction of foundations in private housing construction, in the construction of roads, in the production of slabs. It is often used to create flexible bonds between masonry, to improve the performance of walls, etc.

If you have any experience with composite rebar - please share in the comments!

Composite reinforcement(plastic) in recent years has often competed with conventional steel. This is due to a number of its advantages. But such material has its drawbacks and features of its application. Advertising often interferes with an objective assessment of both, and today the article will present the characteristics of this material, talk about its types and areas of application.

Materials for making

Today the market for composite reinforcement is represented by three types:

• fiberglass;
• basalt-plastic th;
• carbon fiber.

Fiberglass reinforcement

The first type of reinforcement is made of fiberglass. This technology appeared in the USSR about 50 years ago. Then printed wiring began to gain momentum in electronics, and textolite began to be used as a material for boards, when the basis was fabric, and the bonding compound was artificial resin. Later, fiberglass was used instead of conventional fabric, and this expanded the use of fiberglass.

He took his place in the aircraft industry, furniture and household goods, and sometimes even in the military industry. Gradually, it began to be used in construction, and fiberglass reinforcement became an excellent option for foundation frames operating in aggressive conditions - for example, in water.

The materials for fiberglass are glass and epoxy.

This material does not contain fiberglass, but basalt. Its manufacturing technology is simpler than that of glass, because glass production requires several types of raw materials, and for basalt plastic- only basalt.

Compared with the previous composite, basalt-plastic has a higher modulus of elasticity and ultimate strength, has a lower thermal conductivity, but somewhat greater weight.

Carbon Fiber CFRP

It is made from carbon fiber and the same resins, but this material is expensive. This is due to the technology for the production of carbon fiber - the basis of such materials. Technological process requires strict adherence to the parameters of temperature and processing time, since organic fibers serve as the raw material for them.

CFRPs are actively used in the automotive industry, the production of sporting goods, aircraft and shipbuilding, and science.

Carbon fiber reinforcement is stronger than fiberglass and has a higher modulus of elasticity, but it is not without its drawbacks. So, the fragility of this material is great, which does not allow its use in long stressed structures like floor slabs.

Composite rebar production technology

There are three methods for making composite reinforcing bars. They have English names that reflect the essence of the technology.

Needletrusia- this is the twisting of individual fibers into one with simultaneous impregnation and braiding. Allows to reduce the cost of the process due to the high speed of such technological lines. Giving a relief characteristic of the reinforcement is achieved by winding with threads of a periodic profile. The thicker the reinforcement, the more threads are used. So, rods up to 10 mm in cross section are wrapped with one thread, from 10 to 18 - with two, and above - with four. Products made using this method have good adhesion to concrete due to their relief - and this despite the fact that composite materials have a low adhesion coefficient.

Method plantrusions consists in pre-forming the main rod and then winding it spirally in two directions.

The oldest method of making composite rebar is pultrusion... It is a drawing of a formed, impregnated and already hardened fiber through a system of dies, which, at the temperature of plastic polymerization, finally give the reinforcement the desired shape and pull it out. This method is distinguished by a lower production speed and a higher cost price.

Comparison of quality characteristics

You can use the following table to compare different types of composites, and also compare them with steel.

In addition, composite reinforcement has the following property: fragility, which distinguishes it from steel for the worse. Because of this, and also because of its instability to high temperatures, it is not used in structures experiencing strong bending loads and in those places that are at risk of fire.

Advantages of the material

Composite reinforcement has a number of advantages over standard steel. These include:

• Increased tensile strength... It can be several times higher than that of steel.
• Corrosion resistant... Plastic fittings will not rust.
• Low heat transfer coefficient. Unlike metal, plastic does not create cold bridges.
• Plastic fittings do not work as an antenna, because they are dielectric and diamagnetic. Therefore, the probability of radio interference in structures with such reinforcement is zero.
• Low specific gravity... Steel reinforcement is several times heavier.
• The temperature coefficient of expansion is the same as that of concrete, therefore, the formation of cracks for this reason is excluded.

Disadvantages of composite materials

The advantages of composite materials often cannot be fully disclosed due to the disadvantages that reveal themselves in a number of applications. This is primarily:

• Low modulus of elasticity... Plastic reinforcement is not rigid, its elastic deformation is in low limits (that is, the ability to return to its original shape after the termination of the load is lower).
• Fragility... When bending forces are applied, such reinforcement does not bend, but breaks. In this regard, it is impossible to bend it without heating.
• Low heat resistance... When reaching 150 degrees, fiberglass loses its positive properties, and at 300 it simply collapses, while releasing toxic substances. CFRPs have higher operating and limiting temperatures, since they are expensive and more expensive polymers are used in their manufacture, but they are also more fragile than other types. Steel can work up to 600-750 degrees before softening and melting.

Application of composite reinforcement

Composite products have proven themselves very well where static loads are combined with an aggressive environment - for example, in hydraulic structures. Sometimes such reinforcement is used on its own, sometimes - together with steel, which helps to use the advantages of both types and compensate for the disadvantages of each other.

Plastic products in the form of nets are actively replacing steel in brickwork with cladding, where an air gap is provided. Steel meshes gradually corrode, and sometimes this leads to disastrous consequences (a piece of lining may fall off). The composite is devoid of such a disadvantage.

Equivalent replacement

If we consider the table in the previous chapter and the technical characteristics of specific products, then the question of equivalence is decided depending on the conditions in which the structure of reinforced concrete will be used.

Yes, indeed, in terms of tensile strength, steel reinforcement in a cross section of 12 mm can be replaced with fiberglass 8 mm, and steel 18 - with fiberglass 14. But all this is relevant when this reinforcement is only needed to keep the structure from creeping under load. Simply put, this is how strip and slab foundations can be made.

But in situations where there is a deflection, this rule does not work. So, for the manufacture of a lintel or a floor slab, it is required to increase the number of rods by 4 times - after all, the elastic modulus of a composite is by the same amount less. When the loads increase in the middle of the composite-reinforced slab, it really will not burst, but it will bend more, and the result may be pieces of concrete falling on the head.

The low elastic limit makes it difficult to use composites when reinforcing concrete pillars. The compressive strength of concrete is quite high, but with increased loads on a small unit of area, especially if they are uneven, the modulus of elasticity can make a real difference in resistance to fracture.

At the moment, the use of polymer reinforcement is regulated by SNIP 5201-2003, and changes have been made to it in the form of correction factors for calculating such reinforcement in various operating conditions (Appendix L of 2012).

The main nuances of the products

In recent years, the number of companies producing composite rebar (especially fiberglass) has grown many times over, but the quality of their products leaves much to be desired. Here are some ways to recognize a marriage:

• Pay attention to the color of the products. High-quality fittings in one batch are always of the same color. If this is not the case, it means that the temperature regime was violated during production.
• There should be no cracks or delamination. They are easy to see in the cut.
• Fiber breaks reduce the claimed performance. They can also be seen with the naked eye.
• Uneven profile (winding). Most likely, the production used old equipment, where the continuity is disrupted.

Now the requirements for composite materials will be tightened. Steel rolled products are becoming more expensive, and plastic reinforcement has every chance of ousting steel from a fairly large market segment. Undoubtedly, not entirely conscientious manufacturers use this, so you should be on the lookout.