Modern construction technologies involve the use of new materials with improved characteristics. One of the latest developments in scientific and construction organizations is plastic reinforcement. Thanks to the complex 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 safety margin for concrete structures in contact with fresh and salt water, as well as aggressive environments.
Composite reinforcement – fiberglass material for strengthening concrete
Composite fiberglass reinforcement is a new building material made from various fibers:
- basalt;
- glass;
- polyamide;
- carbon.
The name of the polymer reinforcement is determined by the type of fiber 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, and also how fiberglass reinforcement behaves in aerated concrete walls. Modern technology manufacturing, which involves impregnation of a bundle of fibers with a thermoplastic mixture based on polymer components, ensures the required strength of the finished product.
Polymerizing at elevated temperatures, the threads collected in a bundle harden and acquire the required shape. Combining fiber threads can improve performance properties.
Improved adhesion of glass reinforcement to concrete is ensured 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.
The fibers are connected to each other polyester resins composite Plastic fittings - features of building materials
Plastic reinforcement, designed to increase the strength of concrete structures, has its own characteristics.
Main difference of this material– light weight, as well as two-layer construction:
- the inner layer is the core of the rod, consisting of longitudinal threads filled with a composite mixture. The core increases the resistance of the material to tensile 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 resistance of the rods to torsion, and also improves the contact of the polymer reinforcement with concrete.
Polymer threads improve the performance properties of composite rods, which successfully compete with standard metal reinforcement. Distinctive features glass fittings:
- weight reduced by 4-5 times compared to steel rods. The main advantage of the material makes it easier to work and reduce costs associated with transportation;
- The polymer material is twice as durable as steel in terms of tensile strength. This makes it possible to provide the required safety margin 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 compared to steel. Polymer material allows for the construction and repair of houses, preventing the formation of cold bridges;
- possibility of assembly power frames without electric welding. This simplifies the process of fixing the bars and also reduces costs.
Fiberglass is used to produce this construction reinforcement Design features and operational characteristics allow the use of glass reinforcement instead of steel rods to solve a wide range of problems.
Glass reinforcement - types of rods
Plastic reinforcement is 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 strength fundamentals roads and pavements;
- basalt plastic, marked ABP. Easily distinguished by the black color of basalt fibers. Basalt plastic rods are superior to fiberglass rods in their ability to withstand tensile loads, as well as the magnitude of elastic deformation;
- Carbon fiber rods marked UGP are made on the basis of carbon, used in the production of concrete composites. Increased cost of purchasing coal plastic fittings compensated by the working properties of the material, as well as the ease of working with it;
- combined. Reinforcement with the ACC index is made of basalt and glass fibers and is 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 different variations of fitting models, some of which are quite unusual How plastic fittings are made
The production process of polymer reinforcement is carried out on automated lines and includes the following stages:
- Filling the feed module hopper with a polymer composition.
- Feeding composite fibers and ensuring uniform tension.
- Heat treatment of the material to remove water and oil inclusions.
- Loading polymer fibers into a tank with heated binding ingredients.
- Pulling the impregnated threads through a nozzle that winds them.
- Polymerization of the starting material in an oven at high temperature.
- Cooling the resulting rods and cutting them into pieces of the required sizes.
The characteristics of the equipment guarantee the quality of the resulting products.
Scope of glass reinforcement
Polymer reinforcement is 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 brick;
The scope of application of this building material is extensive. - construction of port facilities and special structures to strengthen the coastline;
- covering structures highways and strengthening of concrete slopes;
- construction of protective structures for railways and transport highways;
- production of concrete products requiring prestressing;
- construction of transport interchanges, bridges, overpasses and overpasses;
- construction of concrete structures in seismic zones.
Plastic rods do not require waterproofing, regardless of the choice of structural reinforcement scheme. The use of fiberglass reinforcement for concrete reinforcement and the use of polymer rods is carried out on the basis of previously performed calculations. Employees of specialized organizations are proficient in the technique of calculating reinforced concrete for construction.
Advantages of glass fittings
Developers are interested in what the pros and cons of plastic fittings are. Like all building materials, fiberglass reinforcement has disadvantages and advantages. The main advantages of glass fittings:
- increased safety margin;
- acceptable price level;
- light weight of rods;
- corrosion resistance;
- resistance to aggressive environments;
- reduced thermal conductivity;
Plastic reinforcement in construction today is used more and more often, due to its unique characteristics. - environmental cleanliness;
- long period of operation;
- ease of machining;
- convenient delivery option;
- possibility of assembling frames without welding;
- preservation of properties when negative temperatures;
- dielectric characteristics.
Due to the complex of advantages, composite rods are popular.
Weaknesses of fiberglass rods
Along with the advantages, glass fittings also have disadvantages.
Main disadvantages:
- decrease in strength properties when heated above 200 °C;
- increased likelihood of fire when heated;
- insufficiently high elastic modulus;
- decrease in strength properties during operation and contact with alkalis;
- the impossibility of bending bars without the use of special technological methods.
These disadvantages limit the scope of use.
Not a single more or less large concrete structure is complete without a reinforcing frame. The use of rolled metal of round cross-section for these purposes has become commonplace. And the industry does not stand still and manufacturers are actively promoting its composite counterpart, namely, fiberglass reinforcement.
Interstate standard 31938-2012 regulates general technical specifications on polymer reinforcing products. The material is solid rods of round cross section, consisting of two or more components: base, filler and binder. For fiberglass it is:
- Staple glass fiber, known to every builder as an excellent insulation and reinforcing element.
- Polyamide fiber filler, which gives the finished product an increased degree of tensile and tear strength.
- Polymer thermosetting resins (epoxy, vinyl ester and others).
Composite reinforcement is produced using rods with a cross-section of 4-18 mm. The product is cut and packed either in six-meter bundles or bays (length - up to 100 m). Buyers are offered 2 types of profile:
1. Periodic - corrugation is achieved by the method of spiral winding of a rod with a thin fiberglass bundle. A layer of polymer resin is applied on top to protect the material.
2. Conditionally smooth – finished products is subjected to sprinkling with fine quartz sand to improve the adhesion properties with the concrete composition.
The main purpose is the reinforcement of standard and prestressed structures that are operated in aggressive environments. But since the melting point of synthetic binders starts at approximately +120 ° C, and the combustion temperature - from +500 ° C, the structures being built must meet the fire resistance requirements in accordance with GOST 30247.0-94, as well as the fire safety conditions specified in GOST 30403-2012.
Fiberglass is used in the following areas:
- Construction of enclosing structures in low-rise construction: pile, strip or grillage foundation, multilayer or monolithic walls from concrete, brick, cellular concrete blocks, floors and partitions.
- Construction of road surfaces, sidewalks, sleepers.
- Strengthening screeds, industrial floors, decking, bridge structures.
- Production shaped products, reinforced concrete products.
- Formation of frames for greenhouses, small hangars, panel installations.
Companies engaged in the construction of houses made of wood and wood materials(OSB or chipboard, wood concrete), fiberglass reinforcement is actively used for fastening dowels, intersections, etc. This is due to the fact that hardware over time, they rust, ugly streaks appear, loosening of fasteners and ligaments is possible.
The scheme for forming a reinforcing frame from a composite is identical to the rules for working with rolled metal. The main task is the same - to strengthen the foundation, floor or wall in the area of maximum tensile or bending stress. The horizontal part is located closer to the surface of the structure with a minimum step between the "layers" of up to 50 cm, and the transverse and vertical support elements are mounted at intervals of at least 30 cm.
Advantages and disadvantages
Let's list the advantages of fiberglass composite:
1. Light weight. A composite rod with a diameter of 8 mm weighs 0.07 kg / linear meter, and a metal rod of the same section weighs 0.395 kg / running meter.
2. Dielectric properties. The material is inert to radio waves and magnetic fields, does not conduct electricity. It is thanks to this quality that it is used for the construction of buildings for special purposes: laboratories, medical centers, testing facilities.
3. Chemical resistance. The products are characterized by their inertness to aggressive compounds of acidic and alkaline types (concrete milk, solvents, bitumen, sea water, salt compounds). It is used in areas where the soil is highly acidic or alkaline. The foundation, piles and other similar structures will retain their basic properties even if the concrete part is superficially damaged.
4. Corrosion resistance. Not subject to oxidation, thermosetting resins do not interact with water.
5. The thermal expansion index of glass composite is similar to that of cement concrete, which eliminates the risk of delamination during sudden temperature changes.
6. Easy to transport and install. Packed in bundles of rods or rolled into coils. The weight of the package does not exceed 500 kg, so small freight vehicles or light-duty passenger cars can be used for transportation. For installation, knitting wire or special plastic clamps are used.
Now let's look at the other side of the coin:
1. Temperature limits use of glass composite – from -10 to +120 °C. At sub-zero temperatures, reinforcement becomes brittle and easily breaks under load.
2. The modulus elasticity index does not exceed 55,000 MPa. For comparison, the same coefficient for steel is 200,000. Such a low indicator for a composite means that the rod does not work well in tension. As a result, defects appear on the concrete structure (delamination, cracks).
3. When pouring concrete, fiberglass products exhibit poor stability, the structure wobbles and bends.
4. Plastic clamps are used to tie crosshairs and overlaps. In terms of reliability, they are seriously inferior to knitting wire and welding.
5. Corners, curved areas, points of rod output for subsequent connection with a wall or column are worked out with rolled metal. Fiberglass composite is categorically not recommended for these purposes.
6. High cost of material. If a steel rod with a diameter of 88 mm costs 8 rubles per linear meter, then the price of fiberglass reinforcement is 14 rubles. The difference is not too big, but the purchase volume starts from 200 m or more.
Cost in Moscow
| ASP, section in mm | Price in rubles per linear meter | |
| Corrugated ASP | ASP with sand coating | |
| 4 | 7 | 11 |
| 6 | 9 | 12 |
| 8 | 14 | 17 |
| 10 | 20 | 25 |
| 12 | 25 | 37 |
| 14 | 35 | 47 |
| 16 | 46 | 53 |
Feedback from design specialists is clear: the use of fiberglass composites should be limited exclusively to low-rise construction.
Comparison of fiberglass and metal
Glass composite is positioned as an alternative to rolled metal. Let's do a comparison:
1. Deformation and physical and mechanical properties.
Based on the data in the table, glass composite works worse in tension and does not withstand the same loads as metal. But at the same time, the first type of reinforcement, unlike rolled steel, does not create “cold bridges”.
2. Reactivity.
Metal products are afraid of moisture in any form, as it contributes to corrosion of the product and its splitting. The material can withstand any subzero temperatures without loss of basic properties, and the frame is not afraid of fires - the melting point of steel starts from +1400 °C.
Fiberglass does not react with water, saline, alkaline and acidic solutions, and there is no interaction with such aggressive compounds as bitumen, solvents and the like. However, when the temperature drops below -10 or -15 °C, the product becomes brittle to break. Fiberglass composite belongs to the G2 flammability group (moderately flammable) and in the event of a fire it can create an additional source of fire.
3. Security.
Steel is a material that does not contain volatile impurities such as formaldehyde, toluene and others, so talk about emissions harmful substances unreasonable. The same cannot be said about fiberglass composite. Thermosetting resins are synthetic polymer compositions that contain various toxic components, including phenol, benzene, the well-known formaldehyde, etc. Therefore, fiberglass does not belong to the category of environmentally friendly products.
One more point: metal fittings have been tested by time and vast experience in its use has been gained, there is real reviews. The advantages and disadvantages have become well known, and methods for overcoming the latter have been developed. The confirmed service life is on average 30-40 years, the same cannot be said about glass composite. Manufacturers claim that their material can last no less.
The conclusion from the above confirms the opinion of experts: rolled reinforcement is the leader in almost all parameters and replacing it with fiberglass is irrational.
People's opinions
"When developing a project small dacha the architect proposed for strip foundation use fiberglass. I heard a little about this material, on forums on the Internet, most often the opinion about it is negative. First of all, due to the lack of calculation methods and clear standards for replacing metal with a composite. The developer convinced me of the feasibility of such a solution. Reviews may be different, but you should rely on the recommendations provided by the official manufacturer. The document contained basic instructions: replacement not by equal strength, but by diameter in a ratio of 1 to 4. The house was rebuilt in six months, and there are no signs of destruction on the foundation yet.”
Yaroslav Lemekhov, Voronezh.
“A foam block house is reinforced every four rows according to technology. Both metal and fiberglass composite can be used. I opted for the latter. According to reviews, such fittings are easy to install, there are no difficulties with welding or transportation. It’s very easy and fast to work with, and time costs are reduced significantly.”
Vladimir Katasonov, Nizhny Novgorod.
"For the foundation under frame bath with insulation I wanted to choose newfangled rods, but my neighbor-engineer criticized my positive opinion about the product to smithereens. In his deep conviction, fiberglass in concrete is full of disadvantages with a minimum of advantages. If physical properties metal are similar to the concrete component, it is very difficult to make the composite work with a cement-sand mixture. Because of this problem, negative reviews appear, so I used it for anchoring multi-layer walls. It also has low thermal conductivity."
Anton Boldovsky, St. Petersburg.
“When I built the log house, I used fiberglass reinforcement instead of metal for dowels and joints. I put the rest in the barn, a year later they came in handy. Under brick fence I filled in a small tape and made a full-fledged composite frame for reinforcement. The disadvantages of the material in the form of a low tensile strength coefficient did not prevent me from building a good, durable fence, which has been in service for about three years.”
Evgeny Kovrigin, Moscow.
Scientific progress does not stand still. This also applies to the construction manufacturing sector. Everyday at the market building materials More and more alternatives to outdated products are appearing. The same is true with steel reinforcement. IN last years A product such as composite reinforcement is gaining popularity. This fitting comes in three types: fiberglass, basalt-plastic And carbon fiber. Depending on the type, it is based on either glass, carbon, basalt, or aramid fibers and polymer binders in the form of resins. Externally, it consists of plastic rods with special technological ribs (like steel reinforcement) or a sand coating.
Ribs and sand are applied to the surface to improve the adhesion of the reinforcement to the concrete. Technological process and characteristics composite reinforcement have been known for many years. But, despite this and the bold statements of manufacturers that it is more durable than steel reinforcement, the leadership still remains with steel. Is it possible that it will replace steel and is it as good as the manufacturers praise it? This question can be answered only by considering all the pros and cons of composite reinforcement. 
Advantages of composite reinforcement
Resistance to aggressive environments. Most important advantage all types of composite reinforcement are biological and chemical resistance. This fittings are neutral to the effects of microorganisms and their metabolic products. It is also neutral to water and highly resistant to various alkalis, acids and salts. This allows it to be used in those areas of construction where steel reinforcement shows poor resistance in these parameters.
Such areas may include: coastal fortifications, bridge construction, road construction (where there is exposure to anti-ice reagents), concrete work in winter time, when various plasticizing, frost-resistant and hardening-accelerating additives are added to the concrete mixture.
Relatively light weight. Compared to steel reinforcement, composite reinforcement weighs four to eight times less, which helps save on transportation costs and unloading and loading. In addition, due to the low weight, concrete structures are also lighter, which is important for large scales and volumes of work.
Dielectricity and radiotransparency. Since plastic fittings are a dielectric, this allows you to avoid emergency situations and losses of electricity due to faulty wiring. Also, composite reinforcement does not interfere with radio waves, which is important in the construction of commercial and other types of buildings. 
Long service life. Due to its composition and structure, as well as resistance to aggressive environments, the service life of composite reinforcement is very long. To date, a record of forty years has been recorded. Manufacturers claim that it can last 150 years or more, but since composite reinforcement has been used in construction relatively recently, it is not yet possible to verify this.
Ease installation work . Due to its elasticity, composite reinforcement is twisted into small coils (with a diameter of just over one meter, depending on the cross-section of the reinforcement), which, combined with its low weight, allows it to be transported to passenger car. In addition, installation work can be successfully carried out by one person, since the technology for assembling structures is relatively simple.
Strength. The tensile strength of composite reinforcement is much higher than that of steel. With the same rod diameters, composite reinforcement can withstand longitudinal loads 3-4 times greater than steel reinforcement.
No length restrictions. Due to its elasticity, plastic reinforcement can be twisted into coils of 50, 100 or more meters. While maximum size steel reinforcement is usually limited to 12 meters.
Disadvantages of composite reinforcement
- Poor bending performance. Composite reinforcement has a modulus of flexibility that is three to four times less than steel reinforcement, which can lead to deformation of concrete structures and the formation of cracks. In addition, due to its high elasticity, it is not intended for the manufacture of bent structures (for example, foundation corners).
- Small range of sizes. Due to limited use, composite reinforcement is produced in a smaller variety of diameters than steel reinforcement. The range of produced sections is limited to sizes from 4 to 32 millimeters.
- Limited types of installation work. Installation of structures is carried out only by tying with wire or plastic ties. While steel reinforcement can also be welded.
- Low thermal resistance. At temperatures above 100-120 degrees, composite reinforcement begins to melt and loses all its properties. Therefore, in case of fires in such buildings, their further operation can be dangerous.
- Lack of sufficient documentation and regulatory framework. Although there are GOSTs for composite reinforcement, in most SNiPs, calculations for composite reinforcement are either poorly represented or absent altogether.
- Increased brittleness at low temperatures. Even at low subzero temperatures, composite reinforcement becomes more fragile.
conclusions
Composite reinforcement has a number of advantages and can be successfully used in many areas of construction. But a number of significant disadvantages do not allow it to completely replace steel reinforcement.
Reinforcement of concrete monolithic structures plastic materials is increasingly used in construction. This is due to such performance qualities as high strength, durability and lack of corrosion. The last circumstance is especially important when constructing hydraulic structures, bridges and foundations.
Manufacturers of building materials produce 5 types of composite plastic reinforcement:
- glass composite or fiberglass - ASC;
- carbon composite – AUK;
- basalt composite – ABK;
- aramidocomposite - AAC;
- combined – ACC.
From the name you can understand which material is the basic basis for the manufacture of plastic fittings.
General description and manufacturing technology
Due to its low cost and good performance, fiberglass reinforcement is most widely used. Its strength is slightly lower than other composites, but the cost savings justify its use. For its production use:
- staple fiberglass;
- epoxy thermosetting resins as a binder;
- special polymer additives to increase strength and improve other characteristics.
Composite fiberglass reinforcement for foundations can have a smooth or corrugated surface. According to the manufacturing technology, bundles of the required diameter are initially formed from fiberglass and impregnated with epoxy resin. Afterwards, to obtain a corrugated variable cross-section, the surface of the smooth rod is wrapped in a spiral with a cord, which is also woven from fiberglass. Then the resulting blanks are polymerized in an oven at high temperature and, after cooling, cut into straight sections or wound into coils.
Specifications
Production of periodic profiles and specifications fiberglass reinforcement are regulated by GOST 31938-2012. The standard defines:
- types of plastic fittings depending on the materials used;
- nominal diameters ranging from 4 to 32 mm;
- the length of straight rods is from 0.5 to 12 meters;
- possibility of supplying materials in coils with a diameter of up to 8 mm inclusive;
- markings and symbols;
- quality control methods;
- storage and transportation rules.
Characteristics of types of composite reinforcement. The weight of the material depends on the size of the cross section and can range from 0.02 to 0.42 kg/m.
Weight of plastic fittings. Data on ultimate strength and elasticity given in GOST show that these parameters exceed the characteristics of rolled steel with the same diameters. This allows the use of polymer reinforcement in particularly critical structures or when it is necessary to reduce the cross-sections of reinforcing materials.
Area and method of application
Plastic reinforcement is a modern alternative to rolled metal. The identical shape of the rods allows its use using technology similar to steel. A reinforcement frame made of composite plastic reinforcement is formed in the form of a flat mesh or spatial structure designed to strengthen and increase the strength of reinforced concrete monoliths.
Polymer reinforcing materials are used in the construction of roads, bridges, hydraulic structures, columns, walls, ceilings, foundations and other monolithic structures.
The main load falls on the longitudinal rods of the structure. They have a larger cross-section and are located at a distance of no more than 300 mm from each other. Vertical and transverse elements can be located at a distance of 0.5-0.8 m. The connection of individual rods at intersections is carried out using polymer ties or knitting wire. The joining of individual rods on one horizontal line is carried out with an overlap.
Advantages of plastic fittings
When comparing composite rods with metal rods (we have already carried out a comparison in this article), a number of pros and cons of plastic reinforcement are clearly identified. These include:
- reducing the weight of the reinforcement frame by 5-7 times;
- higher strength, allowing the diameter of the rods to be reduced;
- corrosion resistance and chemicals in the composition of concrete;
- simple installation and high speed of assembly of reinforcing frames;
- simplified technology for creating round and oval structures;
- excellent dielectric and thermal insulation properties;
- ease of transportation.
In addition, it should be noted that the length of rods for materials supplied in coils is unlimited, as well as simple cutting of blanks of the required length.
Reinforcement made on the basis of fiberglass is 20-30% inferior in strength to other composites, but is significantly cheaper. Therefore, such material is in higher demand in construction.
Flaws
Among the main disadvantages of composite reinforcing materials, experts call:
- low maximum temperature of use, not exceeding 60-70°C;
- poor mechanical stability under lateral loads;
- the impossibility of bending with a small angle of curvature and the need to use special elements.
It should be noted that there is no regulatory framework for the use of polymers for concrete reinforcement and, often, unreliable technical data from the manufacturer of the material. This makes calculations difficult and forces structures to be assembled with a safety margin.
Technology of foundation reinforcement with composite materials
The low weight of plastic reinforcement for the foundation simplifies the process of assembling a reinforcement frame of any design. At the same time, due to the increased strength of the material, the cross-sectional diameter is taken one number less than for metal analogues.
The technological process of installing concrete monolithic structures using polymer rods consists of the following stages:
- formwork installation and pour level marking concrete mixture;
- assembly and installation of the reinforcing frame;
- pouring concrete into formwork;
- removal of formwork panels.
Work on the installation of reinforced monolithic structures must be carried out in accordance with the adopted design decisions. The deck configuration must fully correspond to the size and shape of the foundation. As formwork material, you can use standard factory-made panels, boards, moisture-resistant plywood or chipboard. For permanent formwork most often used sheet polystyrene foam.
After assembling and fixing the formwork panels, on their inside, using a water level, mark the upper limit of pouring the concrete mixture. This will reduce the time it takes to complete the job and help distribute the concrete more evenly.
Spatial reinforcing frame for strip foundation
The foundation reinforcement scheme, laying and rod diameter are always indicated in the project. The use of composite reinforcement, especially those based on carbon fiber, makes it possible to reduce the diameter of the rods by one size. The laying of the material must exactly correspond to the calculated data. The frame is assembled on a level area.
The work begins with cutting the workpieces. To do this, pieces of the required length are unwound from the coil and placed on stands at a height of 35-50 mm above the support pad or ground. After this, the transverse jumpers are laid according to the drawing, and at the intersections they are tied with wire or ties. In this way, the bottom row of the spatial reinforcement frame will be assembled.
At the next stage, it is necessary to assemble a grate that is completely similar to the first one, lay it on top and then cut vertical racks design length. The first post is tied at the corner of the flat gratings, the second at the adjacent intersection, as a result, a spatial structure is gradually formed. If there are more horizontal rows, then the second grid is fixed at the required height, and then the next one is fixed. The vertical post in this case is one whole segment.
When assembling the frame, it is necessary to remember that the ends of the reinforcing bars should be located at a distance of 35-50 mm from the formwork. This will create a protective layer of concrete and increase the service life of the structure. For this purpose, it is very convenient to use special plastic clamps.
Plastic fasteners. It is necessary to pour a sand-crushed stone cushion at the bottom of the trench and compact it well. After this, it is recommended to cover the sand layer with geotextile or waterproofing material. This will prevent moisture from entering the concrete and the germination of weeds.
Horizontal reinforcement of slab foundations
When pouring slab-type foundations, horizontal reinforcement technology is used. Its main feature is the absence of turning and adjacent sections. Usually these are two grids located one above the other from long straight rods and vertical posts.
All work is carried out on site. First, according to the design drawing, the lower mesh is knitted, and the upper mesh is laid on top of it. After this, vertical posts are installed, as described for strip structures. The lower mesh must be installed on stands.
Pouring concrete onto a plastic reinforcement frame
Technologically, pouring a concrete mixture is no different from work using steel reinforcement. However, given the lower strength of the material under lateral radial impact, compaction with a vibrator should be done carefully so as not to damage the integrity of the plastic rods.
Not a single foundation and not a single structure, be it a wall or the ceiling of a house, a pile or a bridge span, cannot do without reinforcement embedded in concrete. Currently, new and often exotic materials with supposedly unique properties are appearing on the market, and reinforcement for concrete foundations is no exception to this list.
We are all accustomed to standard metal fittings, which are produced in different diameters and have been used for the second century. But in Lately fiberglass reinforcement has appeared, reviews of which seem to be positive, but the experience of using it for only a few years does not confirm this.
What is fiberglass reinforcement? These are durable rods with a ribbed surface with a diameter of 4 to 20 millimeters, made of fiberglass, basalt composite materials and intended for use in concrete structures instead of steel reinforcement.
Reviews of fiberglass reinforcement are as follows:
― increased tensile strength (for example, reinforcement with a diameter of 8 mm is an analogue of 12 mm metal);
― ease (it is easier metal in 5 times);
― not subject to corrosion;
― resistance to aggressive environments;
- non-conductivity electric current(dielectric);
- low cost;
- does not screen and does not create a screen to radio waves.
It would seem that everything is very beautiful, but the reviews are more like the key theses from the advertising booklets of the sellers of this very fittings than technical reviews which are of primary interest to us.
Having rummaged on the Internet and made some calculations, we have a slightly different picture for this product, but it is technically verified and correct.
To investigate this issue we will need the following terms:
Elastic modulus- characterizes the ability of a solid body to deform elastically under the influence of force.
Yield strength- mechanical stress under the influence of which the deformed body no longer returns to its original state.
Regulatory resistance- a value slightly less than the yield strength, characterizes the maximum structural stress for calculations with this material.
Ultimate tensile strength of concrete- the maximum coefficient of elongation of concrete, at which cracks do not open.
So let’s try to find out the operation of a beam with steel reinforcement D12 mm.
Steel reinforcement A500C with a diameter of 12 mm has the following characteristics:
Elastic modulus 200 GPa
The standard resistance is 500 MPa, which is slightly less than the yield strength of the steel from which the reinforcement is made.
Thus, we obtain approximate values of the maximum load on a reinforcement bar of 4500 kg. The tensile strength of the reinforcement under this load will be about 2.5 mm/m
Manufacturers of fittings place a sign in the documentation with an equivalent replacement of fittings.
The documentation indicates that steel reinforcement A500C with a diameter of 12 mm corresponds to fiberglass or basalt reinforcement with a diameter of 10 mm.
So let’s try to find out the operation of a beam with such reinforcement D10 mm.
Fiberglass or basalt reinforcement with a diameter of 10 mm has the following characteristics:
Elastic modulus 50 GPa
Standard resistance 2000 MPa.
Thus, we obtain approximate values of the maximum load on a reinforcement bar of 10,000 kg.
The tensile strength of basalt reinforcement under a given load will be about 25 mm/m.
Tensile strength of basalt reinforcement under a load of 4500 kg is about 11 mm.
In order to get the same tension as steel (2.5 mm/m), we need to reduce the load on the rod to 1000 kg, or increase the diameter by 2.1 times to 21 mm.
The value of the ultimate tensile strength of concrete is difficult to find, since it depends on a huge number of conditions, but according to some data, ordinary concrete is no more than 3 mm/m.
Thus, all the advantage of the high strength of the reinforcement is lost due to the low modulus of elasticity, i.e., high elongation under load.
The concrete will simply crack and burst in the place where the reinforcement is stretched before the reinforcement breaks.
What do we conclude from? that an equivalent replacement for steel reinforcement D12 mm, class A500C, is fiberglass or basalt reinforcement with a diameter of more than 20 mm.
Builders and developers ask us same question: Is basalt reinforcement with a diameter of 10 mm suitable? steel diameter 12 mm? I’m going to buy reinforcement for a monolithic foundation slab, they said that it’s enough to take 8 mm, because it corresponds to 10 mm steel.
Is it true?
Yes, it does, but only in terms of tensile strength, but before breaking, any reinforcement stretches (elongates), while the reinforced product becomes deformed and then cracks. And they lengthen different materials in different ways, depending on the elastic modulus (how many times less the elastic modulus is, the more strongly the material stretches under the same conditions). So, fiberglass reinforcement (FRP) will stretch approximately four times more than steel reinforcement, with the same cross-section (diameter) and the same load (whatever it may be in a particular structure). This means that in order to obtain the same deformations under the same loads (preserving the properties of the reinforced product), the SPA must be laid approximately four times larger than the steel one (in cross-section). You can use 20mm SPA instead of 10mm steel. Or simply instead of one steel rod, lay four SPA rods of the same diameter. Or six 8mm SPA rods, instead of one 10mm steel...
You just need to take into account that some manufacturers indicate the diameter of the spa with coiling, but the actual working diameter is smaller. This means that when replacing, it will be necessary to proceed from the real diameter and lay even more spa.
Pros and cons of fiberglass reinforcement:
Main advantage- this is only the ease of its transportation, non-corrosion, resistance to aggressive environments and non-conductivity of electric current (dielectric). That, unfortunately, is probably all
Main disadvantage- this is that we have not found where and how we can use all these advantages, including fittings, since there are no regulatory documents for its use, it is not in GOST for production, in SNiP for use, there are no regulatory documents, it is not standardized methods for calculating the minimum percentage of reinforcement, the requirements are not standardized and the adhesion characteristics of composite reinforcement to concrete are not controlled in any way.
And, in conclusion, fiberglass reinforcement has a low modulus of elasticity, low fire resistance of products reinforced with composite reinforcement, it is not possible to manufacture bent reinforcement products at an angle from reinforcement in the state of delivery or at the construction site (only large radii are possible), it is not possible to use it as a compressed fittings, etc., etc.
And of course the price, fiberglass reinforcement is much more expensive compared to steel:
1 m A500S with a diameter of 12 mm - 30 rub.,
1 m of fiberglass with a diameter of 12 mm costs 50 rubles, and given that it is necessary to use a diameter of more than 20 mm, the price of such reinforcement will be 5-7 times more expensive than steel, which is not economically feasible or profitable.
And finally, we offer a free download of the report from the third international symposium that took place on November 9-11, 2011, Prospects for the use of composite reinforcement.
Prospects of FRP Bars application O.N. Leshkevich, Ph.D. tech. Sciences, Deputy Director for scientific work RUE "Institute BelNIIS"
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Fiberglass reinforcement: disadvantages and features
Video duration 24:45
The video shows and tells what composite and metal reinforcement is, its physical and technical data and the IMPOSSIBILITY of its use in structural concrete foundations.
