Fiber-reinforced concrete

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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 [1] – each of which lend varying properties to the concrete. [2] In addition, the character of fiber-reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation, and densities. [3]

Contents

Historical perspective

The concept of using fibers as reinforcement is not new. Fibers have been used as reinforcement since ancient times. Historically, horsehair was used in mortar and straw in mudbricks. In the 1900s, asbestos fibers were used in concrete. In the 1950s, the concept of composite materials came into being and fiber-reinforced concrete was one of the topics of interest. Once the health risks associated with asbestos were discovered, there was a need to find a replacement for the substance in concrete and other building materials. By the 1960s, steel, glass (GFRC), and synthetic (such as polypropylene) fibers were used in concrete. Research into new fiber-reinforced concretes continues today. [4]

Fibers are usually used in concrete to control cracking due to plastic shrinkage and to drying shrinkage. They also reduce the permeability of concrete and thus reduce bleeding of water. Some types of fibers produce greater impact, abrasion, and shatter resistance in concrete. Larger steel or synthetic fibers can replace rebar or steel completely in certain situations. Fiber reinforced concrete has all but completely replaced bar in underground construction industry such as tunnel segments where almost all tunnel linings are fiber reinforced in lieu of using rebar. This may, in part, be due to issues relating to oxidation or corrosion of steel reinforcements. [5] [6] [7] This can occur in climates that are subjected to water or intense and repeated moisture, see Surfside Building Collapse. Indeed, some fibers actually reduce the compressive strength of concrete. [8] Lignocellulosic fibers in a cement matrix can degrade due to the hydrolysis of lignin and hemicelluloses. [9] [10]

The amount of fibers added to a concrete mix is expressed as a percentage of the total volume of the composite (concrete and fibers), termed "volume fraction" (Vf). Vf typically ranges from 0.1 to 3%. The aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter (d). Fibers with a non-circular cross section use an equivalent diameter for the calculation of aspect ratio. If the fiber's modulus of elasticity is higher than the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile strength of the material. Increasing the aspect ratio of the fiber usually segments the flexural strength and toughness of the matrix. Longer length results in better matrix inside the concrete and finer diameter increases the count of fibers. To ensure that each fiber strand is effective, it is recommended to use fibers longer than maximum size of aggregate. Normal concrete contains 19 mm equivalent diameter aggregate which is 35-45% of concrete, fibers longer than 20mm are more effective. However, fibers that are too long and not properly treated at time of processing tend to "ball" in the mix and create work-ability problems.

Fibers are added for long term durability of concrete. Glass [11] and polyester [12] decompose in alkaline condition of concrete and various additives and surface treatment of concrete.

The High Speed 1 tunnel linings incorporated concrete containing 1 kg/m3 or more of polypropylene fibers, of diameter 18 & 32 μm, giving the benefits noted below. [13] Adding fine diameter polypropylene fibers, not only provides reinforcement in tunnel lining, but also prevents "spalling" and damage of lining in case of fire due to accident. [14]

Benefits

Glass fibers can:

Polypropylene and nylon fibers can:

Steel fibers can:

Natural (lignocellulosic, LC) fibers and/or particles can: [15] [16]

Blends of both steel and polymeric fibers are often used in construction projects in order to combine the benefits of both products; structural improvements provided by steel fibers and the resistance to explosive spalling and plastic shrinkage improvements provided by polymeric fibers.

In certain specific circumstances, steel fiber or macro synthetic fibers can entirely replace traditional steel reinforcement bar ("rebar") in reinforced concrete. This is most common in industrial flooring but also in some other precasting applications. Typically, these are corroborated with laboratory testing to confirm that performance requirements are met. Care should be taken to ensure that local design code requirements are also met, which may impose minimum quantities of steel reinforcement within the concrete. There are increasing numbers of tunnelling projects using precast lining segments reinforced only with steel fibers.

Micro-rebar has also been recently tested and approved to replace traditional reinforcement in vertical walls designed in accordance with ACI 318 Chapter 14. [19]

Some developments

At least half of the concrete in a typical building component is used to protect the steel reinforcement from corrosion. Concrete using only fiber as reinforcement can result in saving of concrete, thereby greenhouse effect associated with it. [20] FRC can be molded into many shapes, giving designers and engineers greater flexibility.

High performance FRC (HPFRC) claims it can sustain strain-hardening up to several percent strain, resulting in a material ductility of at least two orders of magnitude higher when compared to normal concrete or standard fiber-reinforced concrete. [21] HPFRC also claims a unique cracking behavior. When loaded to beyond the elastic range, HPFRC maintains crack width to below 100 μm, even when deformed to several percent tensile strains. Field results with HPFRC and The Michigan Department of Transportation resulted in early-age cracking. [22]

Recent studies performed on high-performance fiber-reinforced concrete in a bridge deck found that adding fibers provided residual strength and controlled cracking. [23] There were fewer and narrower cracks in the FRC even though the FRC had more shrinkage than the control. Residual strength is directly proportional to the fiber content.

Use of natural fibers has become a topic of research mainly due to expected positive environmental impact, recyclability and economy. [24] [25] The degradation of natural fibers and particles in a cement matrix is a concern. [26]

Some studies were performed using waste carpet fibers in concrete as an environmentally friendly use of recycled carpet waste. [27] A carpet typically consists of two layers of backing (usually fabric from polypropylene tape yarns), joined by CaCO3 filled styrene-butadiene latex rubber (SBR), and face fibers (majority being nylon 6 and nylon 66 textured yarns). Such nylon and polypropylene fibers can be used for concrete reinforcement. Other ideas are emerging to use recycled materials as fibers: recycled polyethylene terephthalate (PET) fiber, for example. [28]

Standards

See also

Related Research Articles

<span class="mw-page-title-main">Concrete</span> Composite construction material

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures 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.

<span class="mw-page-title-main">Reinforced concrete</span> Concrete with rebar

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 bars (rebar) 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.

<span class="mw-page-title-main">Composite material</span> Material made from a combination of two or more unlike substances

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.

<span class="mw-page-title-main">Rebar</span> Steel reinforcement

Rebar, known when massed as reinforcing steel or steel reinforcement, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface features a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.

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 continuous, staple and super-thin fibers are produced and used. Basalt continuous fibers (BCF) are used for the production of reinforcing materials and composite products, fabrics and non-woven materials. Basalt staple fibers - for the production of thermal insulation materials. Basalt superthin fibers (BSTF) - for the production of high quality heat and sound insulating and fireproof materials.

<span class="mw-page-title-main">Delamination</span> Mode of failure for which a material fractures into layers

Delamination is a mode of failure where a material fractures into layers. A variety of materials, including laminate composites and concrete, can fail by delamination. Processing can create layers in materials, such as steel formed by rolling and plastics and metals from 3D printing which can fail from layer separation. Also, surface coatings, such as paints and films, can delaminate from the coated substrate.

Engineered Cementitious Composite (ECC), also called Strain Hardening Cement-based Composites (SHCC) or more popularly as bendable concrete, is an easily molded mortar-based composite reinforced with specially selected short random fibers, usually polymer fibers. Unlike regular concrete, ECC has a tensile strain capacity in the range of 3–7%, compared to 0.01% for ordinary portland cement (OPC) paste, mortar or concrete. ECC therefore acts more like a ductile metal material rather than a brittle glass material, leading to a wide variety of applications.

Glass fibre reinforced concrete (GFRC) is a type of fibre-reinforced concrete. The product is also known as glassfibre reinforced concrete or GRC in British English. Glass fibre concretes are mainly used in exterior building façade panels and as architectural precast concrete. Somewhat similar materials are fibre cement siding and cement boards.

<span class="mw-page-title-main">Filler (materials)</span> Particles added to improve its properties

Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity, etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. Particulates and fibers are the main subgroups of filler materials. Particulates are small particles of filler that are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.

<span class="mw-page-title-main">Rebar spacer</span> Component of reinforced concrete construction

A rebar spacer is a device that secures the reinforcing steel or "rebar" in reinforced concrete structures as the rebar is assembled in place before the final concrete pour. The spacers are left in place during the pouring to keep the rebars in place. After the pour, the spacers become a part of the structure.

<span class="mw-page-title-main">Textile-reinforced concrete</span> Type of reinforced concrete

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.

<span class="mw-page-title-main">Cellulose fiber</span> Fibers made with ethers or esters of cellulose

Cellulose fibers are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.

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.

<span class="mw-page-title-main">Concrete degradation</span> Damage to concrete affecting its mechanical strength and its durability

Concrete degradation may have many different causes. Concrete is mostly damaged by the corrosion of reinforcement bars due to the carbonatation of hardened cement paste or chloride attack under wet conditions. Chemical damages are caused by the formation of expansive products produced by various chemical reactions, by aggressive chemical species present in groundwater and seawater, or by microorganisms. Other damaging processes can also involve calcium leaching by water infiltration and different physical phenomena initiating cracks formation and propagation. All these detrimental processes and damaging agents adversely affects the concrete mechanical strength and its durability.

Steel fibre-reinforced shotcrete (SFRS) is shotcrete with steel fibres added. It has higher tensile strength than unreinforced shotcrete and is quicker to apply than weldmesh reinforcement. It has often been used for tunnels.

Concrete has relatively high compressive strength, but significantly lower tensile strength. The compressive strength is typically controlled with the ratio of water to cement when forming the concrete, and tensile strength is increased by additives, typically steel, to create reinforced concrete. In other words we can say concrete is made up of sand, ballast, cement and water.

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.

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.

<span class="mw-page-title-main">Self-healing concrete</span>

Self-healing concrete is characterized as the capability of concrete to fix its cracks on its own autogenously or autonomously. It not only seals the cracks but also partially or entirely recovers the mechanical properties of the structural elements. This kind of concrete is also known as self-repairing concrete. Because concrete has a poor tensile strength compared to other building materials, it often develops cracks in the surface. These cracks reduce the durability of the concrete because they facilitate the flow of liquids and gases that may contain harmful compounds. If microcracks expand and reach the reinforcement, not only will the concrete itself be susceptible to attack, but so will the reinforcement steel bars. Therefore, it is essential to limit the crack's width and repair it as quickly as feasible. Self-healing concrete would not only make the material more sustainable, but it would also contribute to an increase in the service life of concrete structures and make the material more durable and environmentally friendly.

References

  1. ↑ Yan, Libo; Kasal, Bohumil; Huang, Liang (May 2016). "A review of recent research on the use of cellulosic fibres, their fibre fabric reinforced cementitious, geo-polymer and polymer composites in civil engineering". Composites Part B: Engineering. 92: 94–132. doi:10.1016/j.compositesb.2016.02.002. ISSN   1359-8368.
  2. ↑ M, Guadagnuolo; G, Faella; G, Frunzio; L, Massaro; D, Brigante (January 1, 2023). "The capacity of GFRP anchors in concrete and masonry structures". Procedia Structural Integrity. XIX ANIDIS Conference, Seismic Engineering in Italy. 44: 942–949. doi: 10.1016/j.prostr.2023.01.122 . ISSN   2452-3216.
  3. ↑ https://www.mdpi.com/1996-1944/15/23/8339 |https://doi.org/10.3390/ma15238339
  4. ↑ Fiber Concrete in Construction , Wietek B. , Springer 2021 , pages 268 ; ISBN 978-3-658-34480-1
  5. ↑ Baena, Marta; Torres, Lluís; Turon, Albert; Barris, Cristina (December 1, 2009). "Experimental study of bond behaviour between concrete and FRP bars using a pull-out test". Composites Part B: Engineering. 40 (8): 784–797. doi:10.1016/j.compositesb.2009.07.003. ISSN   1359-8368.
  6. ↑ Tighiouart, B.; Benmokrane, B.; Gao, D. (December 1, 1998). "Investigation of bond in concrete member with fibre reinforced polymer (FRP) bars". Construction and Building Materials. 12 (8): 453–462. doi:10.1016/S0950-0618(98)00027-0. ISSN   0950-0618.
  7. ↑ Pepe, M.; Mazaheripour, H.; Barros, J.; Sena-Cruz, J.; Martinelli, E. (July 1, 2013). "Numerical calibration of bond law for GFRP bars embedded in steel fibre-reinforced self-compacting concrete". Composites Part B: Engineering. 50: 403–412. doi:10.1016/j.compositesb.2013.03.006. hdl: 1822/26253 . ISSN   1359-8368.
  8. ↑ "PP Fibres | India | XETEX INDUSTRIES PRIVATE LIMITED". Archived from the original on February 27, 2021.
  9. ↑ Li, Juan; Kasal, Bohumil (July 2023). "Degradation Mechanism of the Wood-Cell Wall Surface in a Cement Environment Measured by Atomic Force Microscopy". Journal of Materials in Civil Engineering. 35 (7). doi:10.1061/JMCEE7.MTENG-14910. ISSN   0899-1561.
  10. ↑ Li, Juan; Kasal, Bohumil (April 11, 2022). "Effects of Thermal Aging on the Adhesion Forces of Biopolymers of Wood Cell Walls". Biomacromolecules. 23 (4): 1601–1609. doi:10.1021/acs.biomac.1c01397. ISSN   1525-7797. PMC   9006222 . PMID   35303409.
  11. ↑ ASTM C1116/C1116M - 06
  12. ↑ Mechanical Properties of Recycled PET Fibers in Concrete, Materials Research. 2012; 15(4): 679-686
  13. ↑ "News - Fibres add much needed protection to prestigious tunnelling projects". September 27, 2007. Archived from the original on September 27, 2007. Retrieved February 5, 2017.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  14. ↑ FIRE PROTECTION OF CONCRETE TUNNEL LININGS by Peter Shuttleworth, Rail Link Engineering. UK
  15. ↑ Kasal, Bohumil; Leschinsky, Moritz; Oehr, Christian; Unkelbach, Gerd; Wolperdinger, Markus (2020), Neugebauer, Reimund (ed.), "The Resource Principle", Biological Transformation, Berlin, Heidelberg: Springer, pp. 261–310, doi:10.1007/978-3-662-59659-3_14, ISBN   978-3-662-59659-3 , retrieved April 10, 2024
  16. ↑ Wang, Bo; Yan, Libo; Kasal, Bohumil (March 1, 2022). "A review of coir fibre and coir fibre reinforced cement-based composite materials (2000–2021)". Journal of Cleaner Production. 338: 130676. doi:10.1016/j.jclepro.2022.130676. ISSN   0959-6526.
  17. ↑ Li, Juan; Kasal, Bohumil (April 11, 2022). "Effects of Thermal Aging on the Adhesion Forces of Biopolymers of Wood Cell Walls". Biomacromolecules. 23 (4): 1601–1609. doi:10.1021/acs.biomac.1c01397. ISSN   1525-7797. PMC   9006222 . PMID   35303409.
  18. ↑ Li, Juan; Kasal, Bohumil (July 2023). "Degradation Mechanism of the Wood-Cell Wall Surface in a Cement Environment Measured by Atomic Force Microscopy". Journal of Materials in Civil Engineering. 35 (7). doi:10.1061/JMCEE7.MTENG-14910. ISSN   0899-1561.
  19. ↑ Evaluation report core-construction-products.com
  20. ↑ "Home | Building Design + Construction".
  21. ↑ Bagher Shemirani, Alireza (2022), "Effects of Fiber Combination on the Fracture Resistance of Hybrid Reinforced Concrete", Iranian Journal of Science and Technology, Transactions of Civil Engineering, 46 (3), Springer: 2161–2172, doi:10.1007/s40996-021-00703-x, S2CID   237755564
  22. ↑ Li, V.; Yang, E.; Li, M. (January 28, 2008), Field Demonstration of Durable Link Slabs for Jointless Bridge Decks Based on Strain-Hardening Cementitious Composites – Phase 3: Shrinkage Control (PDF), Michigan Department of Transportation
  23. ↑ ACI 544.3R-93: Guide for Specifying, Proportioning, Mixing, Placing, and Finishing Steel Fiber Reinforced Concrete, American Concrete Institute, 1998
  24. ↑ Wang, Bo; Yan, Libo; Kasal, Bohumil (March 1, 2022). "A review of coir fibre and coir fibre reinforced cement-based composite materials (2000–2021)". Journal of Cleaner Production. 338: 130676. doi:10.1016/j.jclepro.2022.130676. ISSN   0959-6526.
  25. ↑ Hamada, Hussein M.; Shi, Jinyan; Al Jawahery, Mohammed S.; Majdi, Ali; Yousif, Salim T.; Kaplan, Gökhan (June 1, 2023). "Application of natural fibres in cement concrete: A critical review". Materials Today Communications. 35: 105833. doi:10.1016/j.mtcomm.2023.105833. ISSN   2352-4928.
  26. ↑ Li, Juan; Kasal, Bohumil (July 2023). "Degradation Mechanism of the Wood-Cell Wall Surface in a Cement Environment Measured by Atomic Force Microscopy". Journal of Materials in Civil Engineering. 35 (7). doi:10.1061/JMCEE7.MTENG-14910. ISSN   0899-1561.
  27. ↑ Wang, Y.; Wu, HC.; Li, V. (November 2000). "Concrete Reinforcement with Recycled Fibers". Journal of Materials in Civil Engineering. 12 (4): 314–319. doi:10.1061/(ASCE)0899-1561(2000)12:4(314).
  28. ↑ Ochia, T.; Okubob, S.; Fukuib, K. (July 2007). "Development of recycled PET fiber and its application as concrete-reinforcing fiber". Cement and Concrete Composites. 29 (6): 448–455. doi:10.1016/j.cemconcomp.2007.02.002.
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