Dispersed Reinforcement: Revolution in Concrete Technologies

CONTENT

• History of concrete
• Distributed Reinforcement History
• How do fibers affect concrete reinforcement?
• Types of distributed concrete reinforcement:
  • Steel Fiber Concrete:
  • Concrete with man-made fibres:
  • Carbon Fiber Concrete:
  • Glass fiber concrete:
  • Concrete with basalt fibres
  • Concrete with natural (organic) fibers
• When and where to use distributed reinforcement?
  • Here is a list of concrete fiber applications with different fiber types:
  • Advantages of dispersed reinforcement:
  • Disadvantages of dispersed reinforcement:
• ArmoTec ultra-strong polymer macrofiber
• FiberMix® synthetic microfiber
• FiberMix® microfiber for concrete in Ukraine
• PolyMesh® polymer macrofiber
• Polymer macrofiber

Concrete history

To understand what dispersed reinforcement is, it's helpful to remember about concrete as a material. It is an invention as old as the first civilizations in the Mediterranean. Archaeological evidence of the use of concrete leads us back to the 7th millennium BC in what is now Israel and Serbia, where screeds were used in huts that had a concrete-like composition.

As the first on a large scale, a mixture of aggregate, lime, gypsum and water was used by the ancient Assyrians - a people creating a powerful state in Mesopotamia. It was about four thousand years before the creation of Poland.

The Egyptians adopted the method of producing and using concrete from the Assyrians, but it was the Romans who perfected it. They also added volcanic ash (which formed pozzolana) and powdered roof tiles to the mixture of water, gypsum, lime and aggregate. 

Pumice stone was a remarkable achievement, as volcanic ash has the ability to bind in any environment, including water, which explains the wide use of this material, mainly as a hydraulic mortar. Roman bridges and aqueducts from this period (around 200 B.C.) and later ones from the time of the empire still serve well and fulfill their original functions. We are also amazed by the domes of the Pantheon, built in the early 2nd century, weighing 5,000 tons.

Reinforced concrete was invented by the French. The technology of reinforcing concrete with reinforced concrete rods was first presented to the world by Joseph-Louis Lambot in 1855 in Paris. At the World's Fair, he showed a concrete barge reinforced with metal rods, which he made in 1848. The mesh reinforcement method was accidentally discovered and patented in 1867 by gardener Joseph Monier.

Distributed reinforcement history

To know the history of fiber concrete, we have to go back in time to Mesopotamia. In Assyria and other countries in the region, chopped straw and animal hair were added to clay bricks. We can consider this moment as the beginning of the search for methods of strengthening building materials with fiber reinforcement.

At the beginning of the 20th century, the world began to massively use eternit - a concrete product reinforced with asbestos fibres. Currently, due to the harmful impact on human and animal health, asbestos has been withdrawn from production and use (in the EU in 1983, in Poland in 1997).

Research on improving the strength of concrete was conducted simultaneously in many laboratories around the world. In the 1960s, it was discovered that adding shredded wire to concrete significantly improved its properties. Theoretically, concrete reinforced with steel fibers, called reinforced concrete, was presented in 1963 by J. Romualdi and G. Batson, and then put into production. In the 1970s, steel fibers of various shapes began to be used. In the 20th century, methods of reinforcing concrete with polypropylene and glass fibers were also developed.

In the 1980s, experiments were conducted with natural fibers such as sisal, cellulose, bamboo, modern carbon, aramid and other polymer fibers.

According to research and many years of experimentation, the best results are achieved by using steel, polypropylene and glass fibers, and the future undoubtedly belongs to carbon fibers.

The use of fiber concrete with the addition of steel fibers improves strength properties, which is why it is widely used as a material for structural reinforcement, and steel fibers additionally protect against scratches.

Concrete with dispersed reinforcement made of polypropylene and glass fibers is perfect as architectural concrete. Fibers of this type eliminate the risk of shrinkage cracks in the cement matrix.

Concrete reinforced with natural fibers is also increasingly appreciated in the construction industry. This is a reliable way to strengthen the ground. The best way to improve the strength of the soil is to introduce elements with high tensile strength. To ensure the durability of the natural fibers, coconut fibers are used to reinforce the concrete, which are extremely durable.

How do fibers affect concrete reinforcement?

Concrete with dispersed reinforcement is a precast or screed enriched with the addition of fibers of a certain type. In the case of fiber concrete, in addition to the classic ingredients of the mix, such as aggregate, cement and water, added fibers that act as reinforcement are of great importance.

The most important task of the fibers is to prevent the formation of cracks and micro-cracks in fresh concrete, which is why fibers play a key role in the first phase of concrete bonding, i.e. in the period of 2-3 weeks from application. However, the fibers are also beneficial in the long term. Thanks to their use, the quality of concrete, its functional properties and mechanical parameters are significantly improved.

Use of fibers for reinforcement:

• Minimizes the risk of shrinkage cracks across the entire thickness of the section.
• Significantly improves tightness parameters.
• Increases the tensile strength of concrete, which reduces surface plastic cracking.
• Improves the frost resistance parameter.
• Improves fire resistance and prevents concrete spalling during fire.
• Improves structure response to dynamic loads by increasing energy absorption.
• Improves the formability of concrete (ease and precision of filling forms, while maintaining tightness and homogeneity of the structure).
• Allows you to replace anti-shrink mats in foundation, floor and underlay slabs. Evenly distributed fibers effectively improve the parameters of concrete over the entire thickness of the cross-section, and not only on the surface layers.
• In some cases, it allows the use of a thinner concrete section.
• Thanks to the homogeneity and less segregation of ingredients during the production of concrete, the correct addition of fibers in accordance with regulations allows the production of repeatable mixtures with exactly the same parameters.

The technology of reinforcing concrete with fibers allows you to improve most of the basic parameters of the material, including:

• Crush resistance;
• Strength;
• Resistance to mechanical damage;
• Fire resistance;
• Corrosion resistance;
• Abrasion resistance;
• Anti-crushing.

Fibers improve cohesion, so that concrete does not degrade under the influence of moisture, does not delaminate (elimination of the self-dividing phenomenon).

Types of distributed concrete reinforcement:

Concrete with dispersed reinforcement is classified by the type of fibers used for the reinforcement. Dispersed fiber reinforcement is the most common:

• Steel;
• Artificial - polymer and polypropylene;
• Carbon;
• Glass;
• Basalt;
• Natural organic.

Steel fiber concrete:

This modern and extremely durable compound is primarily used for pouring floors, including industrial floors in high-bay warehouses, which are exposed to extremely high loads. This is very important for investors who build on unstable ground, where until recently the only solution was to pour the floor after strengthening the ground with piles. Thanks to steel fiber reinforcement, investment costs can be significantly reduced and a solution much more durable than traditional screeds with meshes can be obtained.

In the production of armaments, plastic steel fibers with high tensile strength (above 2200 MPa) are used. In order for the fibers to play well in the concrete, branched anchor ends are used. Proper clamping of the fibers guarantees no deformations under stress.

In order to avoid the accumulation of fibers in one place, for example in the form of a ball, mix manufacturers use the method of connecting fibers with glue in strips, which facilitates the even distribution of fibers in the screed.

Concrete with man-made fibres:

Multipolymer or polypropylene fibers completely eliminate or significantly reduce traditional steel reinforcement. This solution is very safe and extremely economical - the price of artificial fibers is lower than the price of steel, and the production emits much less CO2 to the environment than mining iron ores and smelting them in steelworks.

Tests have shown that concrete reinforced with polymers or polypropylene is more resistant to cracking, has greater tensile and impact strength, and is more resistant to high operating temperatures.

Synthetic fibers are not only cheaper, but also reduce installation time. The dosage of the fibers is simple, they do not accumulate and mix easily. Plastics do not corrode, so in many cases the choice of this type of material is obvious. Concrete reinforced with synthetic fibers is very well suited for the construction of sewage treatment plants and sewage systems, parts of hydropower plants and sports facilities related to water disciplines.

In addition to environments exposed to water, polymer or polypropylene reinforced concrete is used for the construction of road tunnels, slope guards, mining tunnels and power plants, production halls, warehouses, farm buildings in agriculture (cowsheds, silos, grain warehouses) and other non-specialist structures where stairs, shafts, facades and structural elements are built.

Carbon Fiber Concrete:

Carbon fibers are usually associated with the aerospace, automotive and sports equipment sectors. Lightweight and very strong carbon fibers have also proven to be an excellent component for concrete reinforcement.

The use of carbon fibers allows to reduce the weight of the structure - concrete with carbon fibers is about 75% lighter than a traditional reinforced concrete structure. It is also more durable and flexible. In addition, carbon fibers are corrosion-resistant, which means that carbon concrete lasts longer than metal-reinforced concrete.

Recently, much attention has been paid to the study of concrete parameters using dispersed reinforcements made of carbon fiber fabrics. This type of reinforcement enables the construction of much thinner façade walls, which means a larger area with the same external dimensions of the building. It is worth noting that the execution of this type of reinforcement requires exceptional precision, and it is best to use machines, which is why the future of carbon concrete belongs to precast producers.

Glass fiber concrete:

Experiments with reinforcing concrete with glass were made before World War II. The first works brought only minor successes, because the alkaline environment of the concrete led to the degradation of the glass. In the 1960s, British scientists found a solution by adding alkali-resistant glass fibers to concrete.

The use of glass fibers in reinforcement has brought revolutionary results, especially in terms of weight savings. Glass fibers also improve the watertightness of concrete, increase fire resistance, but do not contribute to increased load or bending strength.

The lightness and resistance to water and fire of concrete with glass fiber are used to build façades in skyscrapers. In the United States, it is the primary material used to cover tall buildings. Boards with a thickness of 1.25 cm are lightweight. A natural stone-like finish adds extra charm to buildings.

As in the case of carbon fibers, the latest invention is glass-textile fiber concrete, which uses a fabric (specifically a mat) made of glass fibers, instead of individual fibers. The use of fabric increased the tensile strength and revolutionized the load capacity. Tests carried out in the laboratories of TU Dresden indicate an increase in load capacity by up to 125% when using a layer made of glass reinforcing fabric. This technology was used in 2006 during the construction of a pedestrian bridge in Oschatz, Saxony, on the grounds of the Horticultural Exhibition. The three-centimeter-thick bridge weighs five tons. If traditional reinforced concrete technology had been used, the bridge would weigh b25 tons.

Concrete with basalt fibres

Basalt fibers are one of the natural materials. They are produced by melting basalt rocks (1400 degrees Celsius). Concrete fibers have a length of 24 to 54 mm, a diameter of 12 to 18 μm (a micrometer is one millionth of a meter) and a rough, uneven surface structure. Basalt fibers are resistant to corrosion and alkaline environment. They tolerate temperature changes and UV radiation very well.

Concrete with basalt fibers is durable and resistant to wear and tear, as well as to extreme temperatures. It is perfect as an insulator of heat and electricity. Importantly, basalt fiber concrete creates a transparent magnetic field in which very precise and sensitive devices, such as radars, can operate without interference. Its advantage is also much lower weight - three times less than steel-reinforced concrete.

Basalt concrete is an ecological material, completely biodegradable. It is used in the construction of special facilities, such as nuclear power plants and skyscraper facades.

Concrete with natural (organic) fibers

The most easily available but least used fibers for dispersed reinforcement are easily degraded by alkali and other organic agents.

During reinforcement, the following applies:

• horsehair,
• sisal,
• coconut fibres,
• cellulose.

Of the materials listed, coconut is the most durable.

When producing concrete with natural fibers, it is important to distribute them evenly in the mix. For this purpose, substances called superplasticizers are used to help achieve the best results.

Due to the different fibers, fiber concrete has different properties. Some of them are described above, explaining the characteristics of each type of concrete with dispersed reinforcement.

In general, fiber concrete can be considered superior to traditional steel concrete reinforcement in many respects. Please list:

• Increased resistance to scratches and cracks (fiber reinforcement prevents the formation of larger scratches and cracks); even when cracking occurs, the concrete does not lose its load-bearing parameters; scratches and cracks that appear only occasionally are much smaller and shallower than in the case of traditional concrete reinforcement;
• Lower own weight leads to a significant reduction in the weight of finished structures, enabling the construction of more compact objects and contributing to saving space for development;
• Concrete with fibers is more plastic and easily adapts to molding, which allows it to be used in the construction of extremely demanding and complex structures with unusual shapes;
• Due to the different types of fibres, this material has significantly higher flexural tensile strength compared to traditional concrete, a difference of three to five times.
• The compressive strength increases by 15-30 percent.
• Increased tensile strength.
• This material is very resistant to impact and mechanical damage, much more than ordinary concrete.
• Greater durability as it has greater abrasion resistance.
• Both shrinkage and creep parameters are reduced by 10-30 percent (creep is the build-up of deformation under continuous load; shrinkage is the reduction in concrete volume caused by physical and chemical phenomena).
• This material is highly frost resistant, fire retardant and waterproof.

Even if the fiber concrete cracks, the fibers prevent its destruction. Fibrins act inside the composite as a binder and prevent the destruction of the structure. The stresses created are transferred and evenly distributed over the entire surface, and additionally, the fibers reduce the risk of shrinkage cracks.

When and where to use distributed reinforcement?

The parameters of concrete with the use of dispersed reinforcement prove its high quality, which is why this building material is widely used.

Until recently, it could be found on the construction of exceptional investments, but now it is a popular material, used more and more often in all areas of construction. It is gradually becoming a standard for building single-family houses.

Fiber concrete is used where financial and time savings are sought, and where high resistance and strength are important, while at the same time low weight.

The use of dispersed reinforcement can be extremely beneficial in the construction of large facilities, especially those where floors are exposed to heavy loads. Examples of such buildings are production halls and warehouses with high storage capacity, as well as industrial facilities.

Concrete buildings with dispersed reinforcement can be erected in various climatic conditions - concrete is resistant to UV radiation and to high and low temperatures.

High resistance to water means that fiber concrete (especially with glass, artificial and carbon fibers) can be used to build objects permanently exposed to water, such as bridges, sewage systems, sewage treatment plants, swimming pools, infrastructure on rowing or canoe tracks, septic tanks, hydroelectric power plants.

The lightness of fiber concrete makes it an ideal material for high-rise façades or structures on less stable ground where building weight is important.

Good thermal and electrical insulation are benefits that enable the construction of fiber-reinforced concrete poles for high-voltage traction.

Concrete with dispersed reinforcement exceeds traditionally reinforced concrete in terms of resistance to bending, impact and mechanical damage.

Here is a list of concrete fiber applications with different fiber types:

• Industrial facilities (mainly floors on the ground and on piles);
• Roads, highways, bridges;
• Power plants;
• Blocks for reactors in nuclear power plants;
• Airports (surfaces with runways and buildings);
• Foundations and interfloor ceilings of residential and public buildings;
• Retaining walls at embankments;
• Water dams, canals, sluices, water reservoirs;
• Wastewater treatment plants, sewers, septic tanks;
• Sports facilities, including water sports;
• Casing pipes and plates;
• Facades of buildings, including skyscrapers;
• Road, mining and power plant tunnels;
• Buildings erected in places with increased seismic activity;
• Railway slopes and railroad tracks;
• Foundations for machines and all other structures exposed to dynamic loads.

Advantages of dispersed reinforcement:

• High resistance to temperature changes (from -30 to +75 degrees Celsius);
• Water resistant, except for steel fiber concrete;
• Less structural weight;
• Increased resistance to disintegration during an explosion or fire;
• High impact and tensile strength;
• High abrasion resistance;
• Minimization of shrinkage during setting, which minimizes cracking and creep;
• Improving the plasticity of concrete elements;
• Good mix cohesion, which facilitates pumping over long distances;
• High tightness, minimizing the risk of micro-cracks and self-dilatation;
• Reduction of concrete consumption;
• Good adhesive properties.

Disadvantages of dispersed reinforcement:

• Difficulties in making some types of fiber concrete yourself, automation is recommended, which increases production costs;
• Need to use small aggregates;
• The need to use concrete plasticizers during mixing;
• Fiber cost.

For an average investor who builds a single-family house or other residential building, the use of dispersed reinforcement in the ceilings means a significant simplification of the construction process, avoiding errors in arranging traditional reinforcement, saving time and reducing costs. Fiber concrete is more durable, which can be judged by the protection of the corners.

The main disadvantage of fibre-reinforced concrete is that it is expensive to produce, which often leads to the material being overlooked where money is to be saved. However, the long-term durability and retention of fiber concrete properties can make it more cost-effective than traditional concrete or reinforced concrete.

The cost of distributed reinforcement depends on many factors, such as the purchase of ready-mixed concrete or the assembly of fibers on site. The prices of fibers vary depending on their type, and the prices of ready-made fibre-reinforced concrete prefabricated units are also determined by the manufacturers on the basis of the quantity ordered and transport costs.

When it comes to making your own fibre-reinforced concrete on site, it's possible, especially with steel or polymer fibres. Fibers are produced by cutting steel wire into specific lengths or by cutting polypropylene string or polymer bags into thin strips. 

The use of glass fiber reinforcement offers many benefits, such as increased flexural strength, resistance to building shrinkage and environmental damage, and improved waterproofing. Fiberglass can be purchased at home improvement stores in the form of small flakes that can be easily mixed with the mortar.

In the case of reinforcement with glass fiber, it is important to select the right amount of fibers, which affects the parameters of the concrete. With the addition of 300 g/m3 of fiber, there is no significant effect on the concrete, the addition of 600 g/m3 extends its life and increases its resistance to moisture and ductility, and the addition of 800 to 1500 g/m3 achieves the best results in terms of strength, flexibility and abrasion resistance.

The use of dispersed reinforcement is becoming more and more popular, and the future indicates that this material can replace traditional concrete reinforcement and reinforced concrete mesh. It is especially recommended for the construction of tall buildings, such as skyscrapers, nuclear power plants, swimming pools, septic tanks, floors on the ground and ceilings.

It is also important to adjust the type of dispersed reinforcement to the specifics of the investment and to properly calculate the amount of fibers required to avoid excessive consumption and unnecessary costs.

ArmoTec ultra-strong polymer macrofiber

ArmoTec® is a synthetic, high-strength polymer macrofiber used to reinforce concrete. Polymer reinforcement fibers are excellent replacements for welded wires and traditional metal fiber reinforcement, especially in concrete environments where high resistance to chemicals and corrosion is required. Reinforcing concrete with ArmoTec® allows the cracking process to be controlled and provides additional reinforcement to the concrete by uniformly distributing a huge amount of fibers throughout its entire area. ArmoTek reinforced concrete is characterized by a three-dimensional reinforcement with increased flexural strength, impact strength and surface abrasion resistance. Thanks to a special corrugated surface, ArmoTec polypropylene fibers ensure excellent adhesion to concrete, increasing their effectiveness, especially in the case of shotcrete.

FiberMix® synthetic microfiber

FiberMix® provides a full range of services from production to finalization. The high-quality concrete microfiber is the result of a well-coordinated production process. Using modern technologies, high-quality raw materials and process automation, we are able to provide our customers with FiberMix® microfiber with exceptional properties and performance. Polypropylene fiber is not only cost effective but also highly effective; only 0.6-0.9 kg of raw material is needed to replace the steel mesh per 1 m3 of concrete. Microfibers distributed in a cement matrix create a three-dimensional reinforcement that significantly strengthens the structure without excessive effort.

FiberMix® microfiber for concrete in Ukraine

Microfiber for concrete is increasingly being used in both private and commercial construction due to its cost-competitiveness compared to traditional reinforcement methods. There are various materials available on the market, but the quality of some of them leaves much to be desired. At FiberMix®, we are fully committed to monitoring every stage of fiber production, from the delivery of raw materials to the packaging of the finished product. This responsibility for the production process gives our customers the confidence that they will receive a product of the highest quality.

PolyMesh® polymer macrofiber

With PolyMesh® polymeric macrofiber, we can reinforce the entire volume of concrete while improving product performance by distributing fibers evenly throughout the volume of concrete. PolyMesh® does not collapse when the concrete vibrates to the lower layer under its own weight, as is the case with steel fibers. Polymer macrofiber is used to reinforce various mortars, especially concrete, which significantly increases the strength and other technical properties of concrete products. Currently, polymer macrofiber is in great demand both in private and commercial construction.

Polymer macrofiber

Modern technologies and materials contribute significantly to the optimization of construction processes. Polypropylene (polymer) fiber is one of these innovations. Buying such material in Ukraine is not a problem, however, this issue must be approached with full responsibility. FiberMix®, as a manufacturer of a full cycle, ensures the highest quality of its products, confirmed by appropriate certificates.