Fiber concrete – savings from century to century

These inventions can safely include the creation of a new building material called fiber-reinforced concrete. Concrete has been arguably the most popular building material for the past 300 years. It is inferior in its physical characteristics to natural building materials, but it wins in terms of ease of use and price. The builders have always sought to increase its durability while reducing the cost.

Concrete at the construction site was not simply poured into the formwork, they were pre-reinforced with metal rods. Reinforced concrete, combining the qualities of stone and metal, has become much stronger.

But the inventors remembered a simpler method of reinforcing building materials that was used by the Egyptians. To strengthen the bricks, straw or even horsehair was added to the composition. The brick became stronger, did not crack when dry and was lighter in weight.

The inventors began to experiment with different materials and in 1874 the English inventor A. Berard registered a mixture of different materials as an additive to concrete. In 1918, in France, X. Alfsen since 1918 began to use the method of concrete reinforcement with steel or wooden drags, and 25 years later in England the first fiber-reinforced concrete was developed and poured into the building..

Striking positive properties of fiber-reinforced concrete are high impact strength, high shear and tensile strength, high frost resistance and water resistance. This will set them apart into a separate group of structural materials with very valuable physical properties and an original structure characteristic only of them..

Fiber concrete is obtained by introducing into the cement mixture a reinforcing fiber (from the English Fiber) cut short or in the form of a mesh. The material for reinforcing concrete is used differently, and the name and classification of fiber-reinforced concrete depends on it.

Classification of fiber-reinforced concrete by fiber material, its strength and popularity:

1. Metal fiber (mainly steel).
2. Glass fiber.
3. Fiber made of synthetic fibers.
4. Fiber made from natural materials (basalt, asbestos).
5. Mixed fiber.

From the name of the fiber used for reinforcing concrete comes the name of fiber-reinforced concrete (steel fiber concrete, glass fiber concrete, etc.). The fibers in the composition of fiber-reinforced concrete are randomly placed and they are introduced in various ways – traditional mixing, spraying, “premixing”. To obtain a directed arrangement of fibers in fiber-reinforced concrete when using steel fiber, a magnet is used, and fiber from artificial materials is laid in the form of a mesh or threads..

Each type of fiber uses its own technology for the production of fiber-reinforced concrete. The production of steel-fiber concrete mix is ​​often carried out in standard concrete mixers. For uniform distribution of fibers in the volume of steel fiber concrete, plasticizers are added, fibers are dosed in, and the volume of the batch is reduced by 25 – 30%.

The mixture is laid in the usual way using standard tools. This method is also used to introduce fiber into concrete mix based on natural materials..

Fiberglass concrete and fiber-reinforced concrete using synthetic fibers are technologically produced by spraying (pneumatic spraying) and premixing. The first method is used directly at the construction site. Spraying is carried out under pressure using special equipment through a spray gun. In this case, fine-grained concrete mortar and chopped fiber are simultaneously fed and they are mixed in a spray gun. When applying the solution by spraying, one-step processing of large areas is possible.

In factories, the method of premixing or preliminary preparation of a mixture of fiber-reinforced concrete is often used. At the beginning of the technological cycle, chopped fiber is added to the fine-grained concrete mixture, followed by mixing. A building structure is made from the resulting premix solution in various ways (vibration compaction, roller molding, roller pressing, extrusion, etc.).

The most commonly used fibers in the manufacture of fiber-reinforced concrete are steel and fiberglass. Fiber-reinforced concrete based on steel and fiberglass meets all the strict requirements of the construction industry. Fiber concrete based on synthetic and natural materials are somewhat inferior to them in strength, durability and ease of use..

Increased requirements are imposed on fiber – strength to physical stress, durability, resistance to the effects of concrete mixture and chemicals, and, consequently, durability of operation. Therefore, when creating steel-fiber reinforced concrete, mainly non-rusting steel grades are used, and alkali-resistant fiberglass of the type “Cem-Phil” (England), “Erfib” (Japan), SC-6 (Russia) is used to create glass fiber reinforced concrete..

Taking into account the physical properties of certain fiber-reinforced concrete, the areas of application at the construction site are somewhat different. Steel fiber concrete is used more at industrial facilities with severe operating conditions. Steel-fiber concrete is used for the production of industrial vibration-resistant structures – floors, railway sleepers, slabs for the construction of airfields and roads, bridges. Given the high strength, they are actively used in the construction of explosion and burglary-resistant structures – banks, defense structures. For the construction of irrigation facilities – canals, drainage dams, tanks for water and other liquids.

Fiberglass concrete is more used in civil engineering and in the construction of construction projects that do not require special strength. It is flexible, easy to use and has an excellent aesthetic appearance when dyes are added. Various decorative structures, facade panels for natural stone, volumetric and curvilinear elements of any shape for the restoration of historical buildings are made from fiber-glass concrete. They can replace traditional roofing materials (slate, ceramic tiles), but unlike them, it is durable and lightweight.

Fiberglass concrete is used in the construction of recreation areas with the construction of fountains, swimming pools and the construction of small architectural forms (benches, flower beds, balustrades, etc.). In industrial construction, it is used as a permanent formwork, especially at hydraulic facilities and chemical industry facilities. Lightweight irrigation systems and drainage systems are constructed from glass fiber concrete, as well as when creating waterproofing coatings for buildings.

Recently, they began to use the technology of block construction of cottages. Panels made of glass fiber reinforced concrete (GRC panel) with interlocking structures are manufactured at the factory with their subsequent assembly on site. Considering the lightness of the material and ease of assembly, the work can be carried out by a small team of builders without the use of heavy construction equipment. The use of dyes and various forms of decor in the creation of block slabs from fiberglass allows you to build beautiful, individual design houses.

Fiber concrete based on polypropylene fibers has a limited area of ​​application, since the fibers have lower mechanical and reinforcing characteristics than steel and fiberglass. It is used mainly for pouring floors in the construction of industrial and civil construction projects..

In some cases, to achieve special technical indicators, fibers from various materials are used simultaneously. Recently, they began to carry out fiber reinforcement of foam concrete. The result is a more durable composite material that retains the positive qualities of foam concrete – low weight with low thermal conductivity.

Exotic materials are also used for concrete reinforcement – jute, sisal, cellulose, nylon and other fibers. The search continues for a better material than steel or fiberglass, and given the development of the chemical industry, it will be found.

One detail should be noted that scares potential customers. Fiberglass concrete has a higher cost (up to 3 times) per 1 cubic meter compared to conventional concrete. This should not be scared, given the high quality indicators of glass fiber reinforced concrete, the total amount for work is less, with an equal bearing capacity with thick-walled concrete products. Additionally, the costs of transportation and the use of light lifting equipment are reduced due to the low weight of the products.

The active use of fiber-reinforced concrete at the construction site allows you to quickly erect elegant, durable modern buildings with lower financial costs.