Fiberglass (composite) mesh:
Lightweight composite fiberglass mesh is made of epoxy resin and fiberglass, it is much lighter than metal and easy to use. Mesh is an almost irreplaceable, most common used building material. The grid itself is made of rods – fastened to each other, forming a lattice that is very strong against all kinds of mechanical and chemical influences. The cells in the grid are most often square, the minimum size is 50×50 mm, but products with larger cells are also produced. Composite mesh is usually produced in rolls or cards (sheets). The mesh width can be up to 1.2 m, while the length can be any value.
The usage of composite meshes halves the formation of cracks. It is widely used in the construction of roads, brick and stone buildings, all kinds of floors, as well as when pouring concrete floors. High temperatures and excessive moisture do not a difference for fiberglass or basalt mesh, unlike its metal counterpart.
Advantages of a composite mesh:
|POLAD ARMATUR A-III (A400C) SINFI||ŞÜŞƏ-PLASTİK ARMATUR|
|Diametr, mm||Çəki, kq||Tondakı metrlərin sayı||Diametr, mm||Çəki, kq||Tondakı metrlərin sayı|
The history of the creation of composite fittings
Fittings made of composite materials, the history of its development and application in the USSR.
The first great interest in non-metallic fittings appeared in the middle of the 20th century because of the following circumstances:
– Reinforced concrete structures became widely used in serious constructions that were to be used in aggressive environments. It was difficult to observe necessary corrosion resistance during the use of steel reinforcement in such conditions.
– There was a need to provide necessary anti-magnetic and dielectric properties of many products and important structures. For example, medical care centres, where MRI was usually installed, and research institutes.
– Development of construction projects that were notable for their complexity and high-technology, required increased strength and lightness of the structures. Such conditions could only be provided by use of composite fittings together with high-strength concrete, known as polymer concrete and fibre concrete.
– A lack of ore extraction that would be suitable for the compensation of continuously growing needs for steel and, as usual, a shortage of alloying additives.
The first continuous Ø 6 mm composite fittings production technology was developed in the USSR in the 70s. At that time, the fittings were made of resistant alkaline fibreglass with low-zirconium composition. Its mechanical and physical properties had been thoroughly researched and studied.
Solid alkali-resistant glass fibre with a diameter of 10-15 microns was first taken as supporting base in high-strength non-metallic fittings; the beam of this glass fibre was combined into monolithic rod due to synthetic resins.
Durability and chemical resistance of fibreglass and fittings in concrete were carefully studied in different aggressive environments. Further, it became possible to obtain the fittings made of fibreglass with the following indicators:
– up to 1500 MPa – rupture strength,
– 50 000 MPa – initial modulus
– 1.8 – 2 t/m3 – density (weight content of the fibreglass was 80%),
– ultimate deformation reached 2.5 – 3% by the time, when working chart showed straight stretching up to the abruption,
– long-term strength of the fittings was 65% of rupture strength, it was in normal temperature and humidity conditions
– 5,5-6,5*10-6 – coefficient of linear expansion.
Under the influence of static loads, initially stressing bending elements with presented fittings were studied. Technological rules on the production of the fittings were prepared and offers for the designing of concrete structures with non-metallic fittings were drawn up, reasonable areas for their use were identified.
Prototypes of electrical insulating traverses of the power transmission line supports were prepared, developed samples were mounted on experimental sections of the power line in Russia, Belarus and other former Soviet republics. Researches were made on the use of fibreglass fittings in the supports of contact network and in pressure pipes.
Fibreglass fittings is widely used at non-ferrous metallurgy enterprises in polymer concrete pools at electrolysis workshops, is used at production enterprises in chemical industry, in slabs of bases and floorings in mineral fertilizer warehouses. However, at that time, it was not possible to completely apply fibreglass fittings on a scale of factory manufacturing.
Non-metallic fittings were widely used in the 70s of the 20th century in constructions made of light concrete, in electrolysis pools, bases, piles, beams and crossbars of overpasses, slope mounting plates, support structures of capacitor banks and in traverses without insulation.
Not far from Rogachev city and Cherven city, two movable warehouses were constructed in 1976. Inclined elements of the arches of upper belt were reinforced with initially stressing fibreglass fittings Ø 6 mm. The rods were located in two grooves, each of which was with cross section of 10×18 mm; they were selected in lower plate of the elements. Supporting surfaces of the elements were reinforced with overlays made of wooden boards with thickness of 20 mm.
The percentage of the wood savings in reinforced bearing elements was 22%, thanks to which the cost of the structure was reduced by 9%, an important reduction in the weight of the structure was 20%. In comparison with similar warehouses of the same capacity, the cost of the entire building decreased by 1.7 times.
Where the floors were made of FAM polymer concrete with fibreglass fittings, the plates were mainly reinforced in longitudinal direction with fibreglass rods Ø 6 mm with initial stress, and in transverse direction – without initial stressing. Distribution reinforcement of the shelf was also performed without initial stressing. Thanks to such a process, huge savings were achieved due to reduced costs for each sq.m. of the plate.
Electrical insulating traverses for the power transmission lines – 10 kV and power transmission lines – 35 kV were developed and studied in 1969. The first operational section for the experiments of the power transmission lines – 10 kV with fibreglass concrete traverses was commissioned near Kostroma in 1970.
The section for the experiments of the power transmission lines – 35 kV with electrical insulating fibreglass concrete traverses was commissioned in Stavropol in 1972. The design of the traverse was based on three initially stressing fibreglass concrete rods bolted together on a steel plate, which was fastened with clamps to the top of reinforced concrete support.
The sections for experiments of power transmission lines – 10 kV in the amount of two started to be operated near Grodno city and Soligorsk city in 1975. Assembly three-beam design of the traverse consisted of two rectilinear initially stressing fibreglass concrete elements: two wires were located on horizontal element, and third wire was attached to the top of vertical one. Steel clamps were used to attach assembly traverse to reinforced concrete support of the power transmission lines. The traverses were made of special electrical insulating concrete. The fittings were composed of four rods Ø 6 mm in each element.
The sections of experimental power transmission line supports for 0.4 and 10 kW with the traverses made of concrete polymer, pre-reinforced with fibreglass fittings Ø 6 mm, were put into use in the vicinity of Batumi city in 1979.
The manufacturing of initially stressing electrolysis pools made of FAM polymer concrete was successfully mastered at non-ferrous metallurgy plant in Ust-Kamenogorsk. The electrolysis pools were reinforced with fibreglass rods Ø 6 mm. The dimensions of such pools in the plan were measured as 1080×2300 mm, with a wall thickness of 100 mm and a height of 1650 mm. In accordance with the plan, walls and bottom of the pools were to be reinforced with double symmetrical fittings, the pitch of the rods of which was 200 mm.
The construction of the very first at that time glued wooden bridge in the world with a length of 9 m was completed in 1975. The project was created by the sub-faculty of “Bridges and Tunnels” polytechnic institute in Khabarovsk. The beams of the bridge with a cross section of 20×60 cm were made of spruce wood, and the beams were reinforced with four fibreglass rods, each of which had a diameter of 4 mm.
The second bridge of such type was built in the USSR across Shkotovka river, Primorsky region in 1981. Six metallic I-beams No. 45 made up the span of the bridge, they were initially stressed with gripping of 12 composite rods Ø 6 mm. Thanks to monolithic reinforced concrete slab, the beams were easily combined. The length of the most span itself is 12 m.
A bridge was built in 1989 on the basis of fibreglass fittings in Khabarovsk region. Five ribbed beams were installed in the cross section of the span with a length of 15 m. The reinforcement of the beams was combined, initial stresses formed in them were made by means of four bunches. Each bunch consisted of 24 fibreglass rods with a diameter of Ø 6 mm and one sample bunch made of steel wire. The beams were reinforced with non-stressed fittings of A-I and A-II class, and it was decided to leave such a method unchanged.