The advantages and disadvantages of using fiberglass
Fiberglass rods used as reinforcement when knitting frames have the following positive qualities:
- rods made of composite materials are much lighter than similar iron products. This feature allows you to reduce the burden on the foundation and, therefore, save on investment;
- fiberglass reinforcement has a higher tensile strength compared to steel reinforcement. This property is used when pouring concrete structures experiencing increased loads, and in other critical elements. Light weight and excellent strength characteristics give the optimal combination, so the novelty quickly gains popularity;
- fiberglass is not subject to corrosion. Metal reinforcement, especially in harsh operating conditions, can not cope with oxidative processes and rusts, as a result, concrete loses its original strength characteristics. In aggressive environments when concreting it is better to use plastic reinforcement;
- plastic is not a conductor of electric current, which also helps to increase the service life of finished products. The metal reinforcing cage wears out and oxidizes more quickly, even if it comes into contact with low currents, therefore, for power transmission towers and other structures associated with an electricity source, it is advisable to choose fiberglass reinforcement;
- a comparison of plastic and metal fittings in terms of overall wear resistance showed that there are no noticeable differences between the two materials;
- The main advantage of fiberglass is its thermal expansion coefficient. This indicator, unlike metal, practically coincides with the coefficient of expansion of concrete. As a result, with temperature changes, reinforcement changes its size in the same proportion as concrete. This feature allows you to avoid the appearance of cracks and chips.
In addition to the advantages, fiberglass reinforcement has limitations:
- the elastic modulus of rods made of composite materials exceeds this parameter for metal by 4 times. A concrete slab with a fiberglass frame will flex more strongly under load than the same slab with a steel frame. When building a concrete roadbed, this feature is a plus - the slabs will last longer without damage. But for floor slabs or other reinforced concrete products where stiffness is required, such an indicator of elasticity is not permissible;
- composite materials do not withstand high temperatures. At +60oWith fiberglass reinforcement begins to lose its properties, soften. Therefore, it is impossible to produce a fiberglass reinforcing frame in concrete elements designed to work in conditions with elevated temperature;
- plastic can not be welded, therefore, when forming frames with a complex, curved configuration, it is better to use metal rods;
- it is easy for metal rods to give the desired curvilinear shape right at the construction site, and in order to bend fiberglass reinforcement at the right angle, you will have to submit an application in advance to the factory where they can perform this operation;
- The disadvantages include a more complex frame assembly scheme at the construction site and insufficient qualifications for most installers. But it is rather the cost of new material that builders are not used to. Over time, this problem will disappear by itself.
Advantages and disadvantages of using metal
To understand which reinforcement is better, metal or fiberglass, you need to consider the pros and cons of steel rods for knitting frames.
TO the benefits metal fittings include:
- material strength. In construction, class A reinforcement is used, with a digital designation from 240 to 500. Such products perfectly serve several decades;
- steel reinforcement does not change its properties under the influence of high temperature;
- metal serves for a long time, while it is not a source of environmental pollution, does not emit harmful substances;
- steel bars for reinforcement have high ductility. They can be given any shape without additional heating right at the construction site;
- metal can be welded. In some cases, only viscous wire reinforcement cannot be dispensed with, you have to use a welding machine. Please note that not all are suitable for welding.
- metal rods, but only class A with letter C (for example, A500C);
- metal does not burn and is not dangerous when exposed to open flame.
TO disadvantages metal fittings include:
- corrosion instability of the metal. If the concrete base cracks, moisture penetrates into the gap, the metal frame begins to rust. The corrosion process weakens the strength of the steel frame and eventually leads to the complete destruction of the reinforcement. To avoid this problem, critical structures use special reinforcement with oxidative processes, reinforcement with the letter K, but the cost of such rods is much higher than conventional reinforcement;
- weight. Metal has a larger mass than plastic, so structures with a steel frame will be much heavier when compared with similar structures, but with fiberglass.
Comparison of plastic and metal fittings
So, what is it all the same to choose - composite reinforcement or metal? It's obvious that the choice depends on the operating conditions and the purpose of the concrete base. It is impossible to assert unequivocally that this or that material is better. In each case, choose a particular material that best meets the challenges.
For example, for the construction of a multi-storey building the main characteristic for the reinforcing cage of floor slabs is elasticity. In this case, the traditional steel bar is best suited, which does not bend even with significant loads on large spans.
But if you need to assemble a frame for the bases working in high humidity (bridge supports, coastal structures), increased corrosion resistance of the reinforcement is required. The way out is to use fiberglass. Also fiberglass armored belts are suitable for pouring a strip foundation under a one-story individual house of aerated concrete or foam blocks.
If we consider the cost of both materials, then a clear answer - which is cheaper, cannot be obtained.
A metal rod with a diameter of 8 mm (24 rubles / m - average prices for winter 2020 in St. Petersburg are given) will cost more than a rod of the same diameter from a composite (11 rubles / m), but it must be borne in mind that the strength of the metal rod lower, and 8 mm reinforcement made of plastic will correspond in its strength characteristics to a steel bar with a diameter of 10 mm.
What is better to use for the foundation and in what cases
It is impossible to unequivocally answer the question - which is better, plastic or metal reinforcement for the foundation, but it should be remembered - in industrial and civil construction, the metal rod is traditionally continued to be used to build the foundation.
Technical characteristics of fiberglass do not allow its use in the construction of large construction projects. When designing multi-storey buildings, power plants, industrial buildings, only steel reinforcement is used.
It is allowed to use fiberglass reinforcement for assembling basement frameworks during the construction of the following objects:
- In low-rise construction for pouring strip foundations.
- For pouring supports under pillars, bases for fences.
- Moorings, coastal structures, docks.
- Grounds for sewer systems.
- Basic elements of bridges.
In other cases, there is no alternative to traditional knitting of a metal frame.