Should you use fiberglass composite rebar? Features, pros and cons for the foundation

Should you use fiberglass composite rebar? Features, pros and cons for the foundation Fiberglass composite reinforcement - are non-metallic rods made of fiberglass, which gives them strength, impregnated with thermosetting resins, as a binder, and cured. Find out in detail in this scientific article. ...

What is fiberglass composite reinforcement?

Fiberglass, which is part of fiberglass composite reinforcement, is obtained by extrusion from melts of inorganic glass with a special chemical composition ... Extrusion is carried out by forcing the melt through spinning dies. The resulting product looks like endless filaments, which are further processed into filaments, or glass rovings.

Thermosetting synthetic resins (phenolic, epoxy, polyester, etc.), thermoplastic polymers (polyamides, polyethylene, polystyrene, etc.) are used as a matrix in the manufacture of composites.

Physically, the body of fiberglass composite reinforcement consists of two parts, conventionally.

  • Should you use fiberglass composite rebar? Features, pros and cons for the foundation The first part is presented in the form of the main trunk, which sets the main strength characteristics in reinforcement, it usually has the form of a bundle of parallel fibers, which are connected by a composite binder of epoxy and polyester resins.

  • The second part is the outer layer, it is responsible for the properties of adhesion of reinforcement to concrete and most often looks like a unidirectional winding of fibers in a spiral (in appearance it resembles the old steel reinforcement, with a periodic profile). Various manufacturers create their own variations in the form of bi-directional filament winding, or sand spraying. The number of variations of the models of the physical body of the reinforcement is limited only by the manufacturer's imagination or by economic considerations.

Fiberglass composite rebar appeared for the first time in the 60s. XX century.

Its appearance was due to the need to replace metal reinforcement in concrete structures that were in aggressive environments. Construction with its use took place in the USSR, USA, Germany, Canada, Japan, Great Britain since the 70s. It was used in construction in combination with lightweight concrete (aerated concrete, arbolite, etc.), and it was also used in the construction of foundations, piles, electrolysis baths, beams, and overpass girders, supporting structures of capacitor banks, slope fixing plates, insulating crossbeams and others designs.

PROPERTIES OF THE REINFORCEMENT

The main properties of fiberglass composite reinforcement is low weight, due to which, it is easy to transport, has good manufacturability when cutting and knitting and also allows the formation of curved sections .

..Fiberglass composite reinforcement has high tensile strength - it is 2.5 times higher than that of metal, has a high chemical resistance in case of exposure to salt, acid, etc. (see table 1).

Should you use fiberglass composite rebar? Features, pros and cons for the foundation

Among its properties, it should be noted that it is a dielectric . Magnetic and electric fields, as well as radio waves, do not have a tangible effect on the strength characteristics, and has radio transparency. The strength indicator remains stable, at low temperatures, due to the same coefficient of thermal expansion with concrete, when these materials work together, there are practically no cracks and gusts in the concrete layer.

At the same time, fiberglass composite reinforcement has a number of tangible disadvantages: its modulus of elasticity is 3.6 times lower than that of steel, as a result of which it has a low degree of resistance to deformation.

The level of fire resistance is also low. Fiberglass composite reinforcement refers to a self-extinguishing material, has a flammability group G - 1, and the maximum operating temperature in concrete is not higher than 200 ° C, when exceeding which it sharply changes its properties, which can cause a sudden destruction of the structure. In this connection, its use in structures that can be exposed to high temperatures is unacceptable.

With the destruction of fiberglass composite reinforcement, there is no yield area and has a fragile character, while having higher strength indicators, but it gives a sharp, sudden, without previously visible defects, destruction of the structure.

Should you use fiberglass composite rebar? Features, pros and cons for the foundation

Fig.

2 . Voltage diagram.

According to S.P. Maksimov, Yu.

B. Bashkova, E.P. Vshivkova - fiberglass composite reinforcement is not recommended for use in concrete girder structures, floor slabs, columns, since there is a low Young's modulus, and as a consequence, rigidity and practically no bending resistance. But the value of other indicators is favorable for the use of fiberglass composite reinforcement in the case of reinforcing the roadway in those areas where there is an aggressive effect of reagents, in strip foundations and others.

Another disadvantage of fiberglass composite reinforcement can be the inability to use electric welding when connecting segments. One of the solutions to this problem is to install a steel tube at the ends of the reinforcing bar (at the factory), and then apply electric welding to them.

CONNECTING WITH CEMENT

Should you use fiberglass composite rebar? Features, pros and cons for the foundation

Fig. 3. The use of fiberglass composite reinforcement

When using light structural concrete, it is possible to improve the thermal and acoustic characteristics, reduce the weight of structures, and increase the fire resistance of the structure.

When calculating and designing reinforced concrete structures, using fiberglass composite reinforcement, the principles are similar to those used during the design of reinforced concrete elements, in cases where the most important element is the combination of the work of concrete and reinforcement. Based on the research of Zinovkina, A.A., Masalov A.V.

- the connection of fiberglass composite reinforcement with concrete is ensured due to the adhesion of cement stone with an epoxy coating, and not due to mechanical engagement of the coils, inside a concrete matrix, as in profiled metal reinforcement

Reinforcement can be of several types: internal, external and combined, which is a combination of the first two.

Should you use fiberglass composite rebar? Features, pros and cons for the foundation

Fig 4. The first concrete pedestrian bridge in Europe with fiber-reinforced concrete.

Should you use fiberglass composite rebar? Features, pros and cons for the foundation Internal reinforcement can be made in the form of discrete, dispersed and mixed. Discrete reinforcement is the use of fiberglass reinforcement in the form of individual rods, flat and spatial frames, meshes.

There can also be combinations, for example, individual rods, grids, etc. Dispersed reinforcement is an additive to the concrete mix during mixing of chopped fibers (fibers), which are randomly placed in the concrete. Using special techniques, it is possible to achieve directional fiber placement. With dispersed reinforcement, concrete is usually called fiber-reinforced concrete.

External reinforcement is especially important if structures are used in an environment that is aggressive towards concrete.

In this case, external sheet reinforcement will simultaneously have three functions: power, protective and act as formwork during concreting.

External reinforcement can also be divided into solid and discrete. With continuous reinforcement, it is a sheet structure that completely covers the concrete surface, with discrete reinforcement - in the form of mesh-type elements or individual strips.

Fiberglass reinforced concrete structures can be produced in several ways. For example, after making a concrete element, it can be dried and then enclosed in a fiberglass sheath, carrying out a multilayer winding with glass material (fiberglass or glass tape) with layer-by-layer resin impregnation.

After polarization of the binder, the winding will take the form of a continuous fiberglass shell. And the whole element will become a pipe-concrete structure. In the second method, a fiberglass shell is first made, and then filled with a concrete mixture.

Depending on the type of polymer binder and fiber that is used in production, the resistance of fiberglass with respect to aggressive environments can also change. During internal reinforcement, it is required to take into account not only the ratio of fiberglass reinforcement to the external environment, but also the nature of interaction with concrete, in a liquid state.

Hardening concrete has an alkaline reaction, in which the aluminoborosilicate fiber can be destroyed. In such cases, protect the fibers with layers of resin or use fibers with a different composition. In cases where non-wetted concrete structures are used, there is practically no corrosion of fiberglass. In the presence of wetted structures, the level of alkalinity in the concrete environment can be reduced by using cement with active mineral additives.

FEATURES OF USE

Fiberglass composite reinforcement is used in low-rise construction - erection of monolithic foundations, laying reinforced belts in walls, mixed reinforcement of floor slabs, etc.

It is also possible to use it when it is necessary to build boat garages, piers, mooring walls, strengthening the coastline. In addition, it is used to produce layered brickwork, create flexible connections for insulating buildings, use it as grids and rods in structures, erect houses from non-removable formwork, and use it to create monolithic foundations.

Should you use fiberglass composite rebar? Features, pros and cons for the foundation
Fastening the reinforcement to each other

You can also add, thanks to the properties, it is advisable to use it when objects are created for electron beam diagnostics, or objects that have strong electromagnetic radiation, which affect the strength of steel reinforcement.

Fiberglass composite reinforcement can be used for restoration work, etc.

Fiberglass reinforcement is increasingly used, also in modern road construction.

This is predetermined by both high specific strength and the presence of high corrosion resistance, frost resistance, and low thermal conductivity.

In structures for which special requirements are imposed, for example, offshore structures, in particular in areas where there is a variable water level.

CONCLUSION: To use reinforcement or not?

Fiberglass composite reinforcement - competitive in comparison with reinforcement made of steel, in terms of physical and mechanical characteristics ...

Its advantages are also low weight, against the background of high strength, the ability to withstand high tensile load. It does not corrode and has low electrical conductivity. It can be made of any construction length, and it does not lose its strength properties at ultra-low temperatures. The service life of those concrete structures where fiberglass composite reinforcement was used increases several times.

Relevant at the moment is the task of finding new binding components, developing a new manufacturing technology or ways to create a prestressed state in order to increase the elastic properties of fiberglass composite reinforcement.

The solution of these problems will make it possible to more actively use it for the manufacture and operation of critical loaded structural elements of buildings and structures.

REFERENCES:

  1. Maksimov, S.P., Bashkova, Yu. B.

    , Vshivkov, EP Experimental studies of the work of fiberglass reinforcement in the reinforcement of concrete structures / [Electronic resource]. / Universum: Engineering: electron. scientific. zhurn. 2015.

    No. 6 (18). URL: https: // 7universum. com / ru / tech / archive / item / 2255

  2. Okolnikova, G. E.

    , Gerasimov, S. V. Prospects for the use of composite reinforcement in construction / [Text] / Construction and architecture / "Ecology and construction" , - OOO "NITsEiS" No. 3, - 2015

  3. Zinovkina, A. A.

    , Masalova A. V., Problems of studying the adhesion of lightweight concrete with fiberglass reinforcement [Text] / Trends in the development of science and education / Research Center "L-Journal", 2017. - 68p.

  4. Dronov A.

    V., Drokin S. V., Frolov N. V.

    Experimental study of adhesion of fiberglass reinforcement with concrete [Text] / A. V. Dronov, S. V. Drokin, N.

    V. Frolov // Industrial and civil construction - 2016., No. 11 -C. 80-83

[1] Maksimov, SP, Bashkova, Yu.

B., Vshivkov, EP Experimental studies of the work of fiberglass reinforcement in the reinforcement of concrete structures / [Text]. / Universum: Engineering: electron. scientific. zhurn.

2015. No. 6 (18). URL: https: // 7universum. com / ru / tech / archive / item / 2255

[2] Zinovkina, A.

A., Masalova A. V., Problems of studying the adhesion of lightweight concrete with fiberglass reinforcement [Text] / Trends in the development of science and education / Scientific Research Center "L-Journal", 2017. - p.

44 - 46.

[3] 2. Okolnikova, G. E., Gerasimov, S.

V. Prospects for the use of composite reinforcement in construction / [Text] / Construction and architecture / "Ecology and construction", - OOO "NITsEiS" No. 3, - 2015 p. 14 - 21

.