Basalt fiber is a material made from extremely fine fibers of basalt, which is composed of the minerals plagioclase, pyroxene, and olivine. It is similar to fiberglass, having better physico mechanical properties than fiberglass, but being significantly cheaper than carbon fiber. It is used as a fireproof textile in the aerospace and automotive industries and can also be used as a composite to produce products such as camera tripods.
The first attempts to produce basalt fiber were made in the United States in 1923 by Paul Dhe. These were further developed after World War II by researchers in the USA, Europe and the Soviet Union especially for military and aerospace applications. Since declassification in 1995 basalt fibers have been used in a wider range of civilian applications.
In the recent days, the various fibers develop and used in the construction, industrial and highway engineering. The steel is mainly used in that various application. Also fiberglass polythene fibers, carbon fibers, polyamide fibers are now developed and also used in construction, industrial and infrastructure development. In that list new one fiber is added, called, as basalt rock fibers.
In many ways, basalt fiber technology is similar to glass fiber technology, except only one material, basalt rock. Basalt continues filaments are made from the basalt rocks in a single step process melting and extrusion process. Technological process of manufacturing basalt filament consists of melt preparation, fiber drawing (extrusion), fiber formation, application of lubricants and finally winding. Basalt fibers are currently manufactured by heating the basalt and extruding molten liquid through a die in the shape of fibers Crushed rock material are charged into bath type melting furnace by a dozing charger, which is heated using air gas mixture or electrically.
Crushed rocks are converted into melt under temperature 12850C to 14500C in the furnace bath. Molten basalt flows from furnace to feeder through feeder channel and feeder window communicate to recuperate. The feeder has a window with a flange connected on slot type bushing and is heated by furnace waste gases or by electrically. The melt flows through platinum-rhodium bushing with 200 holes which is heated electrically. The fibers are drawn from melt under hydrostatic pressure and subsequently cooled to get hardened filaments.
A sizing liquid with components to impart strand integrity, lubricity and resin compatibility is applied, and then filaments are collected together to form ‘strand’ and forwarded to take up devices to wound on forming tube.
By varying the drawing speed of the fiber and temperature of the melt, fibers of wide size range could be produced. For example, a drawing speed of 12m/s and nozzle temperature of 13250C a fiber of 7 micron were produced while at 4m/s and 12850C a fiber of 17 micron was produced.
At the moment, there are around 20 manufacturers of basalt fiber in the world. Two of them are located in Russia, two in Ukraine, one in Ireland, some others in former Republics of the USSR and all others in China.
Basalt fibers have different properties as follows-
In Concrete reinforcement:
Requirement of the moderate strengthening in the civil structures & high fire resistance can be met with basalt fibers. Basalt filaments incorporated unidirectional rods are used as the reinforcement of concrete slabs in hydraulic engineering and construction in seismically hazardous regions. It is also used in reinforcement for bridges, tunnels, railway sleepers etc.
The basalt rebar consisting of 80% of basalt fiber with on epoxy binder offer better mechanical property to the reinforced concrete & are less expensive. Basalt rebar have same coefficient of thermal expansion (8 ppm/0C) as that of concrete, which increases the compatibility & performance in adverse conditions.
In the accelerated weathering tests, basalt fiber shows better results as compared to glass fibers. Exposed to 6000C for 2 hours also results in almost retention of 90% of normal strength while carbon fiber and glass fibers loss their volumetric integrity.
Chopped fibers are used in cement concrete which increases crack resistance and fracture toughness of concrete. It does not give any adverse effect in concrete mixing.
In Building material:
Basalt fibers can also be used in the interiors, partitioning of buildings, fire proof doors, and sound insulations for the building. They have better sound insulation property. It can act as a barrier in the frequency range up to 1800Hz to the extent of 80% to 95%. It is also used as and warmed panels for construction of prefabricated houses such as roofing. Basalt fibers have better thermal insulating properties, almost three times than the asbestos. Basalt fabrics are used as fire blocking material in the public transport systems. Both woven as well as knitted fabrics are used for these applications.
Some other uses are heat protection, friction materials, High pressure vessels (e.g. tanks and gas cylinders), Load bearing profiles, CNG cylinders and pipes, Ship hulls, Car bodies, Sports equipment, Chopped strand for concrete reinforcement, Pultruded rebar for concrete reinforcement (e.g. for bridges and buildings)
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