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Textile-reinforced concrete is a type of reinforced concrete in which the usual steel reinforcing bars are replaced by textile materials. Instead of using a metal cage inside the concrete, this technique uses a fabric cage inside the same.
Materials with high tensile strengths with negligible elongation properties are reinforced with woven or nonwoven fabrics. The fibres used for making the fabric are of high tenacity like jute, glass fibre, Kevlar, polypropylene, polyamides (Nylon) etc. Recently, attention has been given to the use of plant-based fibers (either dispersed or as a fabric) in reinforcement of concrete [1] [2] [3] [4] [5] [6] . The use of plan-based fibers is promising but the individual components are subject to degradation due to the alkaline environment. [7] [8] [9] The weaving of the fabric is done either in a coil fashion or in a layer fashion. Molten materials, ceramic clays, plastics or cement concrete are deposited on the base fabric in such a way that the inner fabric is completely wrapped with the concrete or plastic.
As a result of this sort of structure the resultant concrete becomes flexible from the inner side along with high strength provided by the outer materials. Various nonwoven structures also get priority to form the base structure. Special types of weaving machines are used to form spiral fabrics and layer fabrics are generally nonwoven.
The initial creation of textile-reinforced concrete (TRC) began in the 1980s. Concepts for TRC originated from the Sächsisches Textiforschungs-institut e.V. STFI, a German institute focusing on Textile technology. [10] The first patent for textile-reinforced concrete design, granted in 1982, was for transportation related safety items. These items were specifically meant to be reinforced with materials other than steel. In 1988, a patent was awarded for a safety barrier that used a rope-like reinforcement as its design. This reinforcement was made from concrete waste and textiles, and the innovative arrangement and size of the reinforcing fibers inside was notable. The reinforcements were set in place so that the concrete could be poured in, and the size of the reinforcement was described using diameter and mesh size. [11]
In 1996, German university students created two concrete canoes using textile reinforcement. One boat utilized alkali-resistant glass as its textile reinforcement. To manufacture the glass in a fabric, a process called Malimo-technique was used to keep the glass in one continuous yarn, such that it could be used to make the fabric. The other boat was constructed using carbon fiber fabric as its method of reinforcement. The boats competed in the 1996 Concrete Canoe Regatta in Dresden, Germany, and this was the first time that textile-reinforced concrete was brought to public attention; the boats received an award for their design. [11]
Four factors are important when constructing TRC, which include the quality of the concrete, the interaction between the textile and the concrete, the amount of fibers used, and the arrangement of the textile reinforcement inside of the concrete. [12]
The particle size of the concrete must be carefully selected. If the concrete is too coarse, it will not be able to permeate through the textile reinforcement. For the best results, fresh concrete should be used. To aid in adhesion, chemical admixtures can be added to help the fibers stick to the concrete. [13]
The characteristic features of TRC are its thin structure and malleable nature, as well as its ability to retain a high tensile strength; this is due to reinforcement in the concrete that uses long continuous fibers that are woven in a specific direction in order to add strength. [11] As the result of the varying strength and properties needed to support correct loading, there are many different types of yarns, textiles weaves, and shapes that can be used in TRC. The textile begins with a yarn that is made of a continuous strand of either filaments or staples. The yarn is woven, knit, glued, braided or is left non-woven, depending on the needs of the project. [13] Carbon, AR glass, and basalt are especially good materials for this process. Carbon has good tensile strength and low heat expansion, but is costly and has bad adhesion to concrete. Basalt is formed by melting basalt rock; it is more cost effective than carbon, and has a good tensile strength. The drawback of basalt is when it is placed in an alkali solution, such as concrete, it loses some of its volume of fibers, thus reducing its strength. This means a nano composite polymer coating must be applied to increase the longevity of the construction. AR glass has this problem, as well, but the positives of using AR glass in TRC structure, including its adhesion to concrete and low cost, outweigh these issues. [13]
Textile-reinforced concrete is described as a strain-hardening composite. Strain-hardening composites use short fiber reinforcements, such as yarn made from carbon fiber, to strengthen a material. Strain-hardening requires the reinforcements and concrete matrix surrounding the reinforcement to be carefully designed in order to achieve the desired strength. [13] The textile must be oriented in the correct direction during design to handle the main loading and stresses it is expected to hold. Types of weaves that can be used to make fabrics for TRC include plain weave, Leno weave, warp-knitted, and 3D spacer. [12]
Another important aspect of textile-reinforced concrete is the permeability of the textile. Special attention must be paid to its structure, such that the textile is open enough for the concrete to flow through, while remaining stable enough to hold its own shape, since the placement of the reinforcement is vital to the final strength of the piece. The textile material must also have a high tensile strength, a high elongation before breaking, and a higher Young's Modulus than the concrete surrounding it. [13]
The textile can be hand laid into the concrete or the process could be mechanized to increase efficiency. Different ways of creating textile-reinforced concrete vary from traditional form-work casts, all the way to Pultrusion. When making TRC using casting, the form work must be constructed, and the textile reinforcement must be pre-installed and ready for concrete to be poured in. After the concrete is poured and has had time to harden, the form-work is removed to reveal the structure. Another way of creating a TRC structure is lamination by hand. Similar to casting, a form-work must be created to house the concrete and textile; concrete is then spread evenly in the form work, and then the textile is laid on top. More concrete is poured on top, and a roller is used to push the concrete into the spaces in the textile; this is completed layer after layer, until the structure reaches its required size. TRC can also be created by Pultrusion. In this process, a textile is pushed through a slurry infiltration chamber, where the textile is covered and embedded with concrete. Rollers squeeze the concrete into the textile, and it can take several sized rollers to get the desired shape and size. [12]
Uses of textile reinforced materials, concretes are extensively increasing in modern days in combination with materials science and textile technology. Bridges, Pillars and Road Guards are prepared by kevlar or jute reinforced concretes to withstand vibrations, sudden jerks and torsion (mechanics). The use of reinforced concrete construction in the modern world stems from the extensive availability of its ingredients – reinforcing steel as well as concrete. Reinforced concrete fits nearly into every form, is extremely versatile and is therefore widely used in the construction of buildings, bridges, etc. The major disadvantage of RC is that its steel reinforcement is prone to corrosion. Concrete is highly alkaline and forms a passive layer on steel, protecting it against corrosion. Substances penetrating the concrete from outside (carbonisation) lowers the alkalinity over time (depassivation), making the steel reinforcement lose its protection thus resulting in corrosion. This leads to spalling of the concrete, reducing the permanency of the structure as a whole and leading to structural failure in extreme cases.
Due to the thin, cost effective, and lightweight nature of textile-reinforced concrete, it can be used to create many different types of structural components. The crack control of TRC is much better than that tradition steel-reinforced concrete; when TRC cracks, it creates multiple small fissures, between 50 and 100 nanometers wide. In some cases, the cracks can self-heal, since a 50 nanometer crack is almost as impermeable as a non-cracked concrete. [13] Due to these properties, TRC would be a great material for all different types of architectural and civil engineering applications.
Textile-reinforced concrete can be used to create full structures, like bridges and buildings, as well as large structures in environments with much water, such as in mines and boat piers. [13] As of 2018, the testing procedures and approval for these structures is not available, although it can currently be used to create small components, such as panels. Façade panels would be a convenient use of TRC, due to the material being thinner and lighter than typical concrete walls, and a cheaper alternative to other options. For bridges and building profiles, TRC could add to the strength and overall design of the structure. [13] TRC could also be used to create irregular shapes with hard edges, and could be a novel way to enhance style and architectural design of modern buildings. [12] [11]
Textile-reinforced concrete could also be used to reinforce, repair, or add on to existing buildings, in either a structural or cosmetic basis. Furthermore, TRC could be used to provide a protective layer for old structures or retrofit new elements to an old structure, due to the lack of corrosion associated with this mechanism. Unlike steel, which will rust if a crack forms, TRC does not corrode and will retain its strength, even with small cracks. If carbon fiber fabric is used as the textile, TRC could be used to heat buildings; carbon fiber is conductive, and could be used to support the building, as well as heat it. [11]
Large scale textile-reinforced concrete can be seen in Germany, at RWTH Aachen University, where a pavilion was constructed using a textile-reinforced concrete roof. The roof was engineered using four TRC pieces; each piece was thin and double curved in the shape of a hyperbolic paraboloid. Traditional concrete design would not allow this structure, due to the complex form-work needed to create the piece. RWTH Aachen University also utilized textile-reinforced concrete to create façade panels on a new extension added to their Institute of Structural Concrete building. This façade was made using AR glass and was made much lighter weight and in a more cost effective manner than a traditional façade of steel-reinforced concrete or stone. In 2010, RWTH Aachen University also helped to design a textile-reinforced concrete bridge in Albstadt, Germany, using AR glass as the reinforcement; the bridge is approximately 100 meters long, and is expected to have a much longer service life than the steel reinforced concrete bridge it replaced. [12]
Textile-reinforced concrete is generally thinner than traditional steel-reinforced concrete. Typical steel-reinforced construction is 100 to 300 mm thick, while a TRC structure is generally 50 mm thick. TRC is much thinner due to an extra protective layer of concrete that is not needed for its design. Due to this thinner structure, less material is used, which helps to reduce the price of using concrete, since the amount of concrete needed is also reduced. [12] Since TRC can be used to extend the life of existing structures, it cuts down on the cost of materials and man power needed to tear down these existing structures, in order to create new ones. Instead of replacing old structures, they can now be repaired to add years of service to the lives of their construction. [13]
Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures to a solid over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.
Reinforced concrete, also called ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.
Glass fiber is a material consisting of numerous extremely fine fibers of glass.
A composite material is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions. Composite materials with more than one distinct layer are called composite laminates.
Carbon fibers or carbon fibres are fibers about 5 to 10 micrometers (0.00020–0.00039 in) in diameter and composed mostly of carbon atoms. Carbon fibers have several advantages: high stiffness, high tensile strength, high strength to weight ratio, high chemical resistance, high-temperature tolerance, and low thermal expansion. These properties have made carbon fiber very popular in aerospace, civil engineering, military, motorsports, and other competition sports. However, they are relatively expensive compared to similar fibers, such as glass fiber, basalt fibers, or plastic fibers.
Fiberglass or fibreglass is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinyl ester resin—or a thermoplastic.
Fibre-reinforced plastic is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, aramid, or basalt. Rarely, other fibres such as paper, wood, boron, or asbestos have been used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, though phenol formaldehyde resins are still in use.
Basalt fibers are produced from basalt rocks by melting them and converting the melt into fibers. Basalts are rocks of igneous origin. The main energy consumption for the preparation of basalt raw materials to produce of fibers is made in natural conditions. Basalt fibers are classified into 3 types:
Metallic fibers are manufactured fibers composed of metal, metallic alloys, plastic-coated metal, metal-coated plastic, or a core completely covered by metal.
Warp knitting is defined as a loop-forming process in which the yarn is fed into the knitting zone, parallel to the fabric selvage. It forms vertical loops in one course and then moves diagonally to knit the next course. Thus the yarns zigzag from side to side along the length of the fabric. Each stitch in a course is made by many different yarns. Each stitch in one wale is made by several different yarns.
A geogrid is geosynthetic material used to reinforce soils and similar materials. Soils pull apart under tension. Compared to soil, geogrids are strong in tension. This fact allows them to transfer forces to a larger area of soil than would otherwise be the case.
Glass fiber reinforced concrete (GFRC) is a type of fiber-reinforced concrete. The product is also known as glassfibre reinforced concrete or GRC in British English. Glass fiber concretes are mainly used in exterior building façade panels and as architectural precast concrete. Somewhat similar materials are fiber cement siding and cement boards.
Fiber-reinforced concrete or fibre-reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers – each of which lend varying properties to the concrete. In addition, the character of fiber-reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation, and densities.
Carbon fiber-reinforced polymers, carbon-fibre-reinforced polymers, carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic, also known as carbon fiber, carbon composite, or just carbon, are extremely strong and light fiber-reinforced plastics that contain carbon fibers. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications.
Three-dimensional composites use fiber preforms constructed from yarns or tows arranged into complex three-dimensional structures. These can be created from a 3D weaving process, a 3D knitting process, a 3D braiding process, or a 3D lay of short fibers. A resin is applied to the 3D preform to create the composite material. Three-dimensional composites are used in highly engineered and highly technical applications in order to achieve complex mechanical properties. Three-dimensional composites are engineered to react to stresses and strains in ways that are not possible with traditional composite materials composed of single direction tows, or 2D woven composites, sandwich composites or stacked laminate materials.
Textile-reinforced mortars (TRM) (also known as fabric-reinforced cementitious mortars are composite materials used in structural strengthening of existing buildings, most notably in seismic retrofitting. The material consists of bidirectional orthogonal textiles made from knitted, woven or simply stitched rovings of high-strength fibres, embedded in inorganic matrices. The textiles can also be made from natural fibres, e.g. hemp or flax. When combining plant fibers with mortars, one must pay attention to potential hydrolysis of hemicelluloses and lignin.
In materials science, reinforcement is a constituent of a composite material which increases the composite's stiffness and tensile strength.
The reinforcement of 3D printed concrete is a mechanism where the ductility and tensile strength of printed concrete are improved using various reinforcing techniques, including reinforcing bars, meshes, fibers, or cables. The reinforcement of 3D printed concrete is important for the large-scale use of the new technology, like in the case of ordinary concrete. With a multitude of additive manufacturing application in the concrete construction industry—specifically the use of additively constructed concrete in the manufacture of structural concrete elements—the reinforcement and anchorage technologies vary significantly. Even for non-structural elements, the use of non-structural reinforcement such as fiber reinforcement is not uncommon. The lack of formwork in most 3D printed concrete makes the installation of reinforcement complicated. Early phases of research in concrete 3D printing primarily focused on developing the material technologies of the cementitious/concrete mixes. These causes combined with the non-existence of codal provisions on reinforcement and anchorage for printed elements speak for the limited awareness and the usage of the various reinforcement techniques in additive manufacturing. The material extrusion-based printing of concrete is currently favorable both in terms of availability of technology and of the cost-effectiveness. Therefore, most of the reinforcement techniques developed or currently under development are suitable to the extrusion-based 3D printing technology.
An Automotive textile is a technical textile used in the transportation and automotive industries. The choice of type of automotive textile focuses on aspects of safety, comfort, and aesthetics. These textiles have variety of applications in the automotive industry, such as interior fittings, safety features, sound insulation, and tire reinforcement.
A fiber-reinforced cementitious matrix (FRCM) is a reinforcement system composed by fibers embedded in an inorganic-based matrix, usually made by cement or lime mortar. Plant fibers are a promising area but they are subjected to degradation in the alkaline environment and elevated temperatures during cement hydration.
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