Metal reinforcement is considered a reliable option for forming the “skeleton” of monolithic concrete. And today its importance and necessity in construction is not in doubt, although a new type of reinforcement has appeared on the market and is steadily progressing - composite or fiberglass (FRP). The material can be called “new” quite conditionally; it came to the market 50 years ago. For Russia, fiberglass was irrelevant until recently; we have enough resources to produce our own metal at a reasonable price for construction.
At the same time, fiberglass reinforcement has caught up and surpassed metal in a number of properties, and conclusions about the strength and durability of the material can be drawn from global experience in operating spas.
Structure of composite reinforcement
A building material is made from fiberglass fiber impregnated with a polymer binder in the form of relief rods of a given size - fiberglass reinforcement. Material structure:
- Inner rod. Serves to provide basic functional characteristics. Fiberglass fibers are used in production. They are placed in the structure of the rods in parallel or in the form of braided weaving, then filled with polymer resin.
- External covering. It is performed by winding composite fibers onto an internal rod or by spraying a fine abrasive onto it.
Combination with metal in floor slabs
The floor slab is reinforced in two layers. The load on the floor slab comes from the top down and is distributed across the entire coverage area. Accordingly, the main working reinforcement is located in the lower layer and experiences high tensile loads. The top layer mainly receives compressive loads.
In this case, fiberglass reinforcement is used in combination with metal reinforcement. The top layer must be made of fiberglass reinforcement, the bottom - from metal.
In the mesh itself, the fiberglass composite reinforcement must have a solid appearance without any breaks. If the floor is reinforced using F10 fiberglass reinforcement, then an overlap of 400 mm must be made. All reinforcement joints should be placed in a checkerboard pattern.
Standard sizes and parameters
The diameter of the produced spa varies in the range of 4 – 18 mm. Products are produced in the form of measuring rods or in coils.
The total length of the reinforcement in the coil depends on the technological equipment used in its manufacture. Spas with a diameter of 12 mm or more are offered to the consumer exclusively in the form of rods.
The main parameters affecting the scope of application include the weight of one meter and the diameter of the composite rod.
The winding pitch can be considered an additional characteristic, but today almost all manufacturers produce reinforcement with a pitch of 15 mm.
Armopoyas (seismic belt) between floors of brick or block buildings
The use of fiberglass composite reinforcement when reinforcing an armored belt (seismic belt) between floors of brick or block buildings, due to its high strength characteristics, increases the spatial rigidity of the building and protects the foundation and walls from cracks caused by uneven settlement and frost heaving of the soil.
Areas of application
Due to the demand for fiberglass reinforcement in construction, manufacturers began to offer products not only in the traditional version - coils and rods. Fiberglass reinforcing meshes and ready-made reinforced frames have appeared on the market in various designs in shape and dimensional parameters.
Composite reinforcement is used in a number of construction works and the manufacture of building structures:
- Reinforcement of structures made of monolithic concrete: walls, wells, coatings, foundations.
- Strengthening masonry made of piece wall materials - brick, stone, as well as porous and lightweight blocks of all types.
- In the construction of road surfaces and strengthening of embankments.
- Construction of buildings using permanent formwork technologies.
- Providing flexible connections of load-bearing, facing, reinforcing layers in the construction of multi-layer walls and other structures.
- Manufacturing of power transmission line supports and railway sleepers.
- Use as dowels for fastening thermal insulation of buildings.
- Installation of utilities, sewerage, drainage.
- Creation of reclamation systems.
- Composite products have gained particular popularity among summer residents and owners of personal plots. SPA is used on the arcs of greenhouses, to create decorative and economic fencing, and to support fruit trees.
Foundation slabs
The technology of reinforcing foundation slabs for low-rise construction of no more than three floors using fiberglass composite reinforcement occurs by replacing metal reinforcement with fiberglass according to the table of equal strength replacement.
Correct replacement with fiberglass reinforcement is guaranteed to lead to significant savings in money, because Fiberglass reinforcement is cheaper than metal. The principle of reinforcing foundation slabs with fiberglass reinforcement does not differ from reinforcement with metal reinforcement, but leads to significant savings in installation time.
When replacing metal reinforcement with fiberglass reinforcement, there is no need to reduce the reinforcement pitch.
If it is necessary to lengthen the fiberglass reinforcement rod, the connection occurs in an overlap. The length of the overlap is from 20 to 50 cm.
Knitting of fiberglass reinforcement is carried out with a knitting wire, cutting of fiberglass reinforcement is carried out with a grinder - a grinder.
Ribbed and smooth rods
The ribbed profile of the products is necessary to improve adhesion to the concrete mixture. Sometimes, for the same purpose, the surface of the reinforcement is sprinkled with sand during the hardening process.
Fiberglass rods with a smooth surface cannot have proper adhesion to concrete, which is why they are less in demand as reinforcement for concrete work.
But the price of smooth rods is much lower, so it makes sense to use them as auxiliary products with minimal load when assembling a frame for reinforcement.
Concrete areas for driving and parking.
Before reinforcement begins, a 5 cm layer of crushed stone is poured on top of the concrete pad onto the sand cushion and compacted. Fiberglass reinforcement strengthens the concrete structure, so when constructing a parking lot you cannot do without it. Concreting of the area for driving and parking a car is carried out using fiberglass reinforcement, which is cut into rods of the required length. It is recommended to use fiberglass reinforcement with diameter F6.
The reinforcement frame is made directly at the installation site and does not take much time. Fiberglass rods are placed crosswise and tied with wire at the joining points.
Advantages of composite reinforcement
Thanks to the combination of non-metallic fibers and a binder composite composition, fiberglass reinforcement has acquired additional qualities and properties that are actively used in practice:
- low specific weight, which reduces transportation costs and facilitates installation;
- no welding operations required;
- tensile strength, almost twice that of metal;
- chemical resistance;
- low level of thermal conductivity combined with a wide operating temperature range;
- high dielectric constant.
The advantages of the material itself are complemented by the features of the technological process:
- all core threads are equally stressed, which enhances the strength of the spa;
- the thread flow at the twisting stage is cleared of all kinds of contaminants, which ensures optimal consumption of components during production and helps reduce the final cost of products;
- To increase chemical resistance and enhance adhesion to concrete, the reinforcement is coated with a layer of vinyl ester resin.
Necessary materials and tools for work
Fiberglass reinforcement cannot be welded, it can only be knitted, so the main tool used in installation will be a special crochet hook attached to a wooden or plastic handle. The tool can have different designs and sizes, so the price varies significantly. The most inexpensive crochet hook costs 150-200 rubles, and in order to use it freely, you just need to get a little practice in your hand.
For a large amount of work, you can purchase a cordless knitting gun charged with a wire spool - however, the tool is too expensive for one-time use. Installers often use a screwdriver for this purpose with a homemade hook made from a large nail installed on it. The most convenient way to hold the wire and make twists is with pliers. In general, one connection takes no more than 4-5 seconds.
To assemble a frame from fiberglass reinforcement, you will need annealed wire with a diameter of 1.2 mm or plastic clamps. Plastic fasteners are also needed, due to which a concrete protective layer is created around the “skeleton” of the foundation. Due to its shape, the lower stand is called a stool - the rod is simply placed on its horizontal part. The side lock has the shape of an asterisk, the rays of which provide the necessary indentation. In the center it has a hole into which the reinforcement rod is threaded.
Bottom row of fittings on stands
Recommendations for choosing products
Criteria for selecting a spa for construction work:
- compliance of the product diameter with the declared values;
- quality of winding of the outer layer;
- Availability of quality certificates and material test reports.
If after a visual inspection it turns out that the color of the fittings is darker than that declared by the manufacturer, then it is not recommended to purchase such products. Darkening of the spa means a violation of the temperature conditions during manufacturing, the product is considered burnt, and its technical characteristics do not correspond to the declared ones.
Physical parameters of fiberglass reinforcement material
According to today's requirements, composite rods must be characterized by three main physical parameters, namely:
- Mass of elements;
- Winding distance;
- External as well as internal diameter.
Each individual profile number has its own physical indicators. The only constant parameter is the winding distance, equal to 15 millimeters. The current specifications regulate that composite rods differing in profile size have the following digital designations: 4, 5, 5.5, 6, 7, 8, 10, 12, 14, 16 and 18. These digital values correspond to the outer diameter parameters. The mass of reinforcing rods can vary from 0.02 to 0.42 kg/1 running meter.
Comparison of the characteristics of steel and fiberglass reinforcement
You should not compare and evaluate steel and composite reinforcement, dividing it into “good” or “bad” based on a set of characteristics. There are precise definitions of when fiberglass reinforcement should not be used, and when it may be the best solution.
As a rule, the justification for any choice is the technical characteristics of fiberglass reinforcement and its metal competitor.
Comparison of these types of fittings is inevitable, since they have similar parameters and areas of application, which means they can be mutually replaced if certain conditions are met.
Strip foundations
Reinforcement of a strip foundation using fiberglass reinforcement occurs by replacing metal reinforcement with fiberglass reinforcement according to the equal-strength replacement table.
Table of equal replacement of metal reinforcement with composite fiberglass reinforcement
| Metal class A-III (A400C) | Composite polymer fiberglass reinforcement OZKM (AKS) |
| 6 A-III | 4 AKS |
| 8 A-III | 5.5 AKS |
| 10 A-III | 6 AKS |
| 12 A-III | 8 AKS |
| 14 A-III | 10 AKS |
| 16 A-III | 12 AKS |
| 18 A-III | 14 AKS |
| 20 A-III | 16 AKS |
Correct, equal-strength replacement of metal reinforcement with fiberglass will allow you to receive economic benefits of up to 45%
(savings 2 times).
When replacing metal reinforcement with fiberglass, there is no need to increase the number of layers of reinforcement and the number of rods in one layer.
If it is necessary to lengthen the fiberglass reinforcement rod, the connection occurs in an overlap. The length of the overlap is from 20 to 50 cm.
Knitting of fiberglass reinforcement is also carried out using a knitting wire; cutting of fiberglass reinforcement is carried out with a “grinder”.
Flaws
The popularity of fiberglass reinforcement is justified by a number of undoubted advantages, but the material also has disadvantages that can cancel out all the advantages.
Low modulus of elasticity
This indicator means that composite products should not be used to reinforce monolithic floors or sections thereof. If it is absolutely necessary to use SPA, it is necessary to carry out careful technical calculations.
Low thermal stability
Fiberglass reinforcement is a self-extinguishing material that cannot spread fire in concrete structures. But at high temperatures, spa products sharply lose their functional strength characteristics, which limits the scope of application of composite reinforcement.
Loss of strength
Fiberglass reinforcement reduces or loses its strength characteristics over time (polymer organic bonds are destroyed - the so-called “aging” process of organics). The process is accelerated when the reinforcement is exposed to alkaline environments. To avoid this drawback, composite products with the addition of rare earth metals should be used.
Taking into account all the listed, even unique advantages of fiberglass reinforcement rods, their use is allowed only in conditions and structures where the material will not experience destructive loads and impacts.
Blind areas around buildings
A blind area is a strip with a width of 0.6 m to 1.2 m, which is adjacent to the foundation or base of a building with a slope.
The slope of the blind area must be at least 1% (1 cm per 1 m) and no more than 10% (10 cm per 1 m).
It is recommended to construct a blind area around the building using fiberglass reinforcement, since the main task of the blind area is to drain surface rain and melt water from the walls and foundation of the house. A blind area using fiberglass reinforcement will last several times longer, since fiberglass reinforcement has high anti-corrosion properties, which prevents the occurrence of cracks in concrete.
Nuances and features
As with any relatively new building material, there are many conflicting opinions about SPA in professional and amateur circles. Let's try to understand the authenticity and validity of some judgments.
About SPA bending
The need to bend reinforcement often arises during construction, directly on site. But fiberglass rods cannot be bent efficiently directly at the installation site - this is what distinguishes it from metal. Builders often consider this a disadvantage of the spa, but not critical. There are two acceptable solutions:
- Bent elements are ordered from the manufacturer in advance if there is a reinforcement design or at least an understanding of the need for bending.
- It is possible to use mixed reinforcement. In this case, composite rods are connected to corner elements made of metal reinforcement.
About the regulatory framework for the use of spas
Opponents of fiberglass reinforcement in construction argue that its use on construction sites is illegal, since there are no regulations and standards for its use. This is just a half-truth. In fact, the use of composite rods is permitted by GOST; no one has the right to prohibit the implementation of a project with expertly verified load calculations. But there is a problem - the lack of programs and approved structural calculation models for the use of composite reinforcement. But for low-rise construction there is no need for such standards and programs. It is possible to build a small house or cottage using a spa, for which you can use approximate standards and advice from knowledgeable professionals.
About the color of composite rods
The initial, standard color of the SPA is light yellowish. As a rarer option, black, if the source material is basalt. Color is intended to make composite rods attractive; this is more of a marketing move, it is not caused by necessity. But there has been some kind of information leak on the market: supposedly coloring additives in the composite improve its characteristics.
Therefore, let’s put the point straight away: color does not in any way affect the quality of fiberglass reinforcement. Perhaps color schemes play some role when using spas for household needs in dachas and gardens.
Reinforcement of industrial concrete floors
Reinforcement of industrial concrete floors using fiberglass composite reinforcement occurs by replacing metal reinforcement with fiberglass reinforcement according to the equal-strength replacement table.
Correct replacement of fiberglass reinforcement when reinforcing industrial concrete floors also leads to significant savings in money, because Fiberglass reinforcement is cheaper than metal.
The principle of reinforcement with fiberglass reinforcement does not differ from reinforcement with metal reinforcement, but leads to significant savings in installation time.
When replacing metal reinforcement with fiberglass reinforcement, there is no need to reduce the reinforcement pitch.
If it is necessary to lengthen the fiberglass reinforcement rod, the connection occurs in an overlap. The length of the overlap is from 20 to 50 cm.
Knitting of fiberglass reinforcement is carried out with a knitting wire, cutting of fiberglass reinforcement is carried out with a grinder - a grinder.
Construction technology.
To build a strip foundation, precise calculations and a specific action plan are used. To begin with, dig a trench 30-80 cm in length. Its dimensions are calculated from the necessary measurement data, weight and area of the future structure.
Then, depending on the type of land, conditions and overall mass, the filling depth is calculated. The usual standard depth ranges from 60-80 cm, but with individual calculations, the depth of the strip foundation can be completely different.
A kind of cushion layer is created with the addition of gravel, which will improve installation. It needs to be watered very heavily. Fiberglass reinforcement is created for a strip foundation with an area of 10 mm. Its installation takes place on bricks or other possible supports with the expectation that 5-10 cm remains from the bottom.
The initial rods are mounted with a registration and program distance from the walls of the pit of 10 cm, then the vertical and transverse posts are tightly secured at an equal interval of 40 cm. The first two upper rods of reinforcement are fixed on them and tied together with transverse rods.
Fiberglass reinforcement.
Types of fiberglass reinforcement.
The form (formwork) of the foundation is made. To do this, take an edged board 25 mm wide and knock together rectangles of the required size (taking into account the measurements of the foundation), which should be about 30 cm above the ground level. After this, a box is assembled from the prepared rectangles and installed in place of the foundation, Place spacer bars and sprinkle the soil.
The finished form is filled with concrete. If support pillars were used, they must be mounted and precisely aligned with the concrete pouring level. This is all done based on calculations and data obtained.
