Reinventing concrete with textiles
Textile-based composites have been studied extensively in the past two decades as they are used in the construction of newly fabricated structural elements and the strengthening of existing structures.
The advancement in construction materials and technology has led to research into efficient and sustainable structural systems that incorporate the properties of minimum material usage, light weight, and added economic benefits. To attain this, researchers impregnated a certain number of fibres into the concrete matrix as they are effective in reducing cracks and can improve the ductility behavior of concrete by making the sections more compact, which can ultimately lead to more economic designs. The alternative method is to replace the steel reinforcement with textile (fibre) mesh, creating textile-reinforced concrete (TRC). The nonmetallic nature of TRC eliminates the usage of concrete cover, resulting in slender members.
Textile-based composites have been studied extensively in the past two decades as they are used in the construction of newly fabricated structural elements and the strengthening of existing structures. TRC possesses enhanced properties such as increased flexibility and resistance to fire. Therefore, TRC is becoming progressively more attractive for strengthening existing structures, in comparison to the more extensively used fibre-reinforced polymer (FRP).
Numerous studies have been conducted globally to assess the suitability of TRC as a building material, in terms of its tensile and flexural strengths. Typically, the specimen is prepared in the form of plates and is subjected to either tensile or three-point bending tests. The results are highly dependent on the type of fibre and the mix design of concrete used. In terms of the bond strength, the majority of researchers have attempted to quantify the bond strength of externally bonded fibre, as TRC is used as a repair material. In textile-reinforced concrete, as the fibre is embedded within the concrete matrix, a new and better bond strength model must be established specifically for this application. This is important for the correct prediction and modeling of the behavior of TRC using numerical analysis. Thus, a comprehensive review of TRC would be useful to provide a holistic picture and allow a wider application of this material in the future.
The novelty of this article is that it applied the science mapping approach (SMA) in the research domain of TRC by using a bibliometric search and scientometrics analysis to reduce the biases. In addition, the current article is further extended with an in-depth qualitative discussion by assessing the existing research on TRC with the following research objectives: to determine (a) the material properties of TRC, (b) the composite behavior of TRC, (c) the bond-slip relations, and (d) the applications of TRC as structural elements. This is followed by a discussion of the recommendations for future research.
1. Bibliometric literature search
The present article adopted a comprehensive approach for evaluating the recent research outputs in the field of TRC from 2010 to 2022 (February) published in Scopus. The research framework illustrated in Figure 1 consists of three sections, namely (i) literature retrieval, (ii) scientometrics analysis, and (iii) qualitative analysis through specific research areas. The literature is divided into four research areas: (A) the material properties of TRC, (B) the composite behavior of TRC, (C) the bond-slip relations, and (D) the applications of TRC as structural elements. This is based on the common theme found in the literature review conducted.
Figure 1: Workflow for reviewing the literature on TRC
1.1. Literature retrieval
The literature retrieval on TRC articles was performed using Scopus, which is considered the major search engine for academic publications. The literature search was performed by entering the following keywords in Scopus: TITLE-ABS-KEY (“textile reinforced concrete, TRC, textile fibres, and textile shells”). The keywords search identified relevant articles published from 2010 to 2022 (February). As shown in Figure 1, a total of three substeps were performed to screen-out articles that were out of scope and did not focus on TRC.
1.2. Scientometric analysis on keywords and publication sources
The text-mining tool (VOS Viewer), developed by, was adopted in the current article for the enhanced analysis and visualisation of the bibliometric studies. This study utilised VOS Viewer to achieve the following key objectives: (i) to obtain the downloaded literature data from Scopus, (ii) to study the mainstream research keywords and their inter-relationships, and (iii) to visualise, compute, and analyse the publication sources and countries belonging to the TRC research community.
1.2.1. Keyword network analysis
The keyword-based literature search in Scopus produced 1097 articles, from which the initial screening removed any articles that were out of the TRC scope (i.e., those that included few other polymers along with TRC). The second set of screening was performed on TRC with a specific focus on engineering applications, leading to a dataset of 510 articles for review. Based on the recommendations proposed by, in the present article, “Author Keywords” and “Fractional Counting” were used in the VOS Viewer analysis.
The minimum occurrence of a keyword was set at 5. Initially, 302 out of 3263 keywords met the threshold, from which some general items were removed to reduce the effect of regular topics, e.g., “reinforced plastics”, “concrete buildings textile industry”, and “steel fibers”. Various other keywords with the same semantic meanings, such as “textile reinforced concretes” versus “textile reinforced concrete”, “bearing capacity” versus “load bearing-capacity”, “FEM” versus “finite element method”, and “mechanical properties” versus “mechanical behavior” were combined in the second-round keyword analysis. Finally, a total of 29 keywords were selected, as shown in Figure 2
Figure 2: Co-occurrence of keywords in TRC research.
The node sizes, distances among the nodes, and connection lines among the keywords are shown in Figure 2 and display the most frequently studied terms. The node colors were used to divide the keywords into different clusters. The font and node size visually represent the number of articles from the given journals, with larger fonts and node sizes indicating larger numbers of publications. The clusters represented by different colors and connection lines indicate the closeness among the keywords in terms of mutual citations.
1.2.2. Periodical publications
The literature retrieval was conducted for publications from the years 2010 to 2022 (February) based on the keyword analysis. The study of TRC is a newly emerging research area, in which a significant number of publications were produced after 2010. In total, 510 publications were found within the last 11 years, with 313 coming from journals. Figure 3 illustrates the number of yearly publications on TRC and shows the increasing trend in recent years.
1.2.3. Research streams of textile-reinforced concrete
Based on the selected papers, the mainstream research work on TRC can be categorised in terms of (A) the material properties of TRC, (B) the composite behavior of TRC, (C) the bond-slip relations, and (D) the applications of TRC as structural elements.
Most articles on TRC fall within research areas (A) and (B), showing that studies of material properties and composite behavior are still ongoing. A significant number of articles (135) discuss the material properties of TRC (A), including the evaluation of bending and shear strength], the effect of elevated temperature and fire, freeze-thaw cycles, and dry-wet cycles. In addition, some publications detail the self-sensing ability of the carbon fibre embedded in the concrete by means of electrical resistance for structural health monitoring. In the area of the composite behavior of TRC (B), 108 articles focus on using textiles as a retrofitting material and a complementary substance in the sandwich sections. In detail, these articles discuss the mechanical behavior of structural elements strengthened with TRC, sandwich composite faces, the dynamic and fatigue responses of composites, and the prestressing behavior of TRC beams. The studies on TRC further focus on bond-slip relations (26 articles) and application as a structural element. In the aspect of research on bond-slip relations (C), most articles explain the bond behavior [37,38], pull-out response of fibres, and interface relations through numerical and experimental methods. Articles related to TRC applications (D) address the evolution, fabrication, and design of TRC as structural elements such as shells, facade panels, and bridges.
The research papers on TRC have been published in 84 different journals. . As shown, the leading two journals in this area are Beton- und Stahlbetonbau and Construction and Building Materials. The main themes in these publications are the material properties of TRC (A) followed by the composite behavior of TRC (B).
1.2.4. Countries focusing on textile-reinforced concrete
The distribution of TRC-based publications according to countries has been determined. The two countries leading the research in this area are China and Germany, accounting for approximately 60 per cent of the total publications. The large number of publications in these countries reflect their focus on using sustainable materials and technology. In countries such as China and France, 75 per cent of their research is conducted on the use of TRC in retrofitting technology (e.g., strengthening columns or beams). Germany is the most advanced country in terms of using TRC as a reinforcing material (e.g., application as sandwich facades, shells, and bridges). In regard to international collaborations, researchers from Germany have collaborated widely with those from other countries, such as Israel, Sweden, and Austria. However, other countries are still in the early stages of adopting TRC technology; hence, the research is limited to the determination of material behavior rather than its applications.
For this analysis, the minimum number of both documents and citations for a country was set at 5. This resulted in a total of 20 out of 40 countries that met the threshold. It is found that the network lines indicate the citations of TRC research undertaken jointly between different countries. According to the size of the regional nodes and the density of the connecting lines, the China, Germany, USA, Canada, and Israel regions were found to be the most active in collaborating with other regions, despite the number of publications.
2. Discussions on TRC research areas
2.1. Material properties of TRC
TRC is a composite structure, which consists of the textile fibre and the concrete matrix. The typical properties of the concrete and the textile embedded in it are discussed in the following sections.
2.1.1. Textile fibre
Steel has traditionally been used as a reinforcing material in concrete due to its high tensile strength and ductile behavior. However, steel is often associated with high carbon emissions during production and higher cost due to the depletion of natural resources. Moreover, steel requires sufficient concrete cover for corrosion protection, causing larger sections in an otherwise slender member. Possible substitutions for steel as reinforcement have been explored and the usage of textile reinforcement has been proposed by many researchers.
Fibre, yarn, and fabric are various forms of reinforcement that have been used as reinforced fibre composites. Textile reinforcements were initially used in the form of chopped and short fibres. The use of mesh or continuous reinforcement has been explored over the past two decades because of its flexibility and ability to be fabricated into complex shapes. Fibres can be classified into two types, natural and man-made fibres. The main sources of natural textile fibres are animals, plants, and natural minerals, whereas synthetic materials and ceramics fabricated using mineral fibres are considered as man-made. Natural fibres made of animal products are not applicable in the construction field, while plant-produced fibres could be used to some extent by having them chemically treated. The most suitable and commonly used fibres in engineering structures are synthetic fibres because of their enhanced mechanical properties and stable nature. Different fibres have been listed along with their mechanical properties. It is found that manmade fibres typically have higher tensile strength and elastic modulus compared to natural fibres, making them preferable for use in structural applications.
A set of combined fibres interlocked and used for sewing, weaving, or knitting is called yarn. A single yarn (filament) typically has a diameter of 5–30 µm and, when combined in thousands, is called roving. The major issue with using textiles directly as reinforcement is their poor bonding in concrete. To improve the bonding of yarns in concrete, three manufacturing techniques have been developed: cabled, friction-spun, and commingled yarns.
Fabric is a combination of a group of yarns. They are classified based on the manufacturing procedure, namely woven, nonwoven, and knitted. Woven fabrics are produced by weaving a set of yarns interlaced perpendicularly. The yarns that run along the length of the fabric are known as warp yarns, while those on the other side are called weft yarns. For construction applications, leno-type fabrics are used, whereby two sets of warp yarns are twisted around the weft yarn to form a grid-like structure. It is common to find textile fabrics woven in the form of a mesh, with specific mesh sizes in the warp and weft directions. The presence of a mesh increases the bond between the concrete and the textile, thus increasing the overall structural strength. Mesh sizes between 5/5 and 10/10 mm (warp/weft directions) are commonly used in structural applications (for example)
Three types of materials are mainly used as textile reinforcement, namely carbon, AR glass, and basalt. Carbon textile is abundantly used in TRC. The properties explaining its frequent usage include its high ductility, tensile strength (1100–4000 MPa), and Young’s modulus (150–235 GPa). Commonly used mesh sizes are 5/5–8/8 mm (warp/weft directions). This material is widely used in shells, slabs, and most structural applications. The next most widely used fibre in TRC is AR glass textile. It has a tensile strength of 120–790 MPa and a Young’s Modulus of 30–40 GPa, and it is less ductile than carbon fibre. Commonly used mesh sizes are 5/5–10/10 mm. Based on the mechanical properties, this material is limited to secondary structural applications such as facade panels, formwork, and non-load-bearing partition walls. The fibre least commonly used in TRC is basalt. This material is always used with coated resins because of its low mechanical properties in comparison with the other available fibres. The tensile strength of basalt (with coating) ranges from 490 to 890 MPa and its Young’s Modulus ranges from 28 to 45 GPa. Commonly used mesh sizes are 5/5–25/25 mm. This material is one of the more sustainable alternatives and is used in riverbanks (bunds) and nonstructural elements.
A comparison of the stress-strain relationship of steel and carbon textile mesh reinforcements. Steel reinforcement yields at a stress of fs,y corresponding to the strain of εs,y (approximately 0.3 per cent). Upon yielding, the steel undergoes significant ductility until it fails at the ultimate stress and strain of fs,u and εs,lim, respectively. In comparison, carbon textile reinforcement has a lower initial stiffness compared to steel, up to the strain of εt,1. An increase in stiffness occurs beyond εt,1 as the yarns elongate. Brittle failure occurs once the ultimate limit strain εt,lim has been reached, which prevents the widespread use of textile reinforcement.
2.1.2. Coatings
When filaments are bundled, microscopic gaps are formed between the fibres that cannot be penetrated by the cement matrix, causing a nonhomogeneous textile-cement composite. Due to this, only the outer end filaments will be strained, resulting in the straining of only 35 per cent of the roving capacity. To overcome these effects, the textiles are coated to stabilise the inner structure of the filaments, ultimately increasing their tensile strength. By coating the textile reinforcement, the load can be transferred more homogeneously among the filaments that enhance the load-bearing capacity, producing a smoother response to loads. Coatings such as epoxy resin or styrene-butadiene have shown encouraging results in terms of tensile stress and maximum ultimate strain. Epoxy resin is generally used for planar members or molded reinforcements such as facades and web reinforcement for T-beam bridges. Meanwhile, rolled-up sections such as temporary reinforcements used for renovations are produced using styrene-butadiene as the fibre coating. Experimental work was carried out by to compare the effect of coatings (epoxy resin and styrene-butadiene) on two different fibre materials, namely AR-glass and carbon, in terms of the load-carrying capacity and stress-strain behavior. The results showed that the fibres coated with epoxy resin achieved considerably higher tensile strength compared to those coated with styrene-butadiene. Researchers have coated the textile surface with sand to increase the bond strength and ultimately increase the bearing strength of the element.
Figure 8: Comparison of different textiles and coatings under tensile stress.
Based on the extensive literature review, carbon fibre mesh with an epoxy coating is the most common type of fibre reinforcement used for structural applications due to its high tensile strength. AR glass with a coating is also widely used in non-load-bearing structural elements as it is cost-effective and shows good bonding behavior with concrete.
2.1.3. Cement matrix
The cement matrix for TRC comprises binders, fine-grained aggregates, and a low water-to-binder ratio. The matrix has to be designed to be physically and chemically compatible with textile reinforcement. When choosing the binding material, the main parameters are (i) its high strength, based on the application, (ii) a sufficient bond between the reinforcement and cement matrix, (iii) its workability during fabrication and setting, (iv) its geometrical stability, (v) the production process, and (vi) low shrinkage and creep. The rheological properties of concrete (incorporated with textile reinforcement) are enhanced by various compositions of the cement-based matrix. The most frequently used binder content for TRC is 40–50 per cent, with a water-to-binder ratio ranging from 0.29 to 0.40. An increase in binder content improves the bonding of mortar with reinforcement. The grain size ranges from 1 to 2 mm, depending on the mesh size of the reinforcement used.
The addition of pozzolans in the cement matrix increases its alkalinity. However, there are no concerns in maintaining the pH balance as the textile used in TRC is alkali-resistant. The mineral admixtures often used in TRC include fly ash, micro silica, and metakaolin. Due to their small particle size and highly pozzolanic reactivity, these materials improve the bonding and mechanical performances. Durability is ultimately improved due to their lower permeability. A substantial replacement of cement with fly ash increases the dicalcium silicate (C2S) content, which leads to an increase in carbonation.
The hardened concrete properties are assessed based on mechanical behavior during compression and tension. The typical application of TRC demands special concrete that is more durable, more ductile, and stronger than normal concrete. Based on the literature, the typical compressive strength used in the cement matrix is 50–60 MPa for structural applications (for example,. A higher strength of 120 MPa has also been used for filigree construction and bearing applications in architecture.
2.1.4. Cost analysis
Similar to conventional reinforced concrete, the production cost of TRC-fabricated elements depends on the fibre used, the type of structural application, and the labor costs. For instance, if a structure is designed to resist major chemical attacks, then high-strength fibre (with high-cost carbon) should be selected as reinforcement. In addition, polymer-based coatings are also applied, which increase the overall cost. For normal applications such as shells and facades, low-cost textiles (basalt or glass fibres) can be used.
The concrete cost will also vary depending on the type of structural application. For instance, when constructing a traditional reinforced concrete flat slab, grade 30 concrete is used (fck = 30 N/mm2). If TRC is used instead, a self-compacting concrete of grade 45 (fck = 45 N/mm2) is required to avoid vibration during material placing. Even though TRC requires higher concrete strength, a slender section can be designed that reduces the overall material cost compared to that of conventional concrete. In addition, the concrete used for TRC possesses high workability, which reduces the labor cost, based on the simplified placement of textile mats and the ease of concrete casting when self-compacting concrete is used. Moreover, the time-dependent costs, such as those of equipment and scaffolding, can be minimised using TRC.
(This is the first part of the article; the second will appear in our next edition.)
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About the author:
* A Jothimanikandan and Dr N Gokarneshan are from the the Department of Textile Chemistry, SSM College of Engineering, Komarapalayam, Tamil Nadu.
* Dr C Kayalvizhiis from the Department of Textile Technology, RVS College of Engineering and Technology, Dindigal, Tamil Nadu.
* Dr M Ezhilarasi, N Sakthivel and MVignesh are from the Department of Civil Engineering, SSM College of Engineering, Komarapalayam, Tamil Nadu.
* K K Hema is from the Department of Mechanical Engineering, SSM College of Engineering, Komarapalayam, Tamil Nadu.
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