A Review-strengthening of reinforced concrete beams with textile-reinforced concrete

Numerous problems that can occur during regular building use may necessitate the need for reinforced concrete RC members to be strengthened. An increase in live loads or structural damage is two examples. Various techniques can be used to increase load-carrying capability. Concrete reinforcement with textile-reinforced materials (TRC) is a more recent option. For almost all active forces, this strengthening procedure is appropriate. For bending, shear, torsion, or axial forces, strengthening is an option. Due to their many appealing qualities, characteristics as their high specific strength (i.e., strength to weight ratio), resistance to corrosion, the convenience of use, speedy installation, and little variation in cross-section, (TRC) have become more and more popular among structural engineers for strengthening and retrofitting projects The conclusions made from the experimental results of members made of reinforced concrete strengthened in shear suggest that textile-mortar composites greatly increase shear resistance, with the gain increasing with the number of layers. This review focuses on strengthening RC beams in flexure by textile-reinforced concrete. According to the authors, TRC jacketing is a very promising technique for increasing reinforced concrete components’ confinement, in addition to their shear and bending capability, which is necessary for seismic retrofitting and strengthening.


Introduction
The need for structural retrofitting of older Reinforced Concrete (RC) structures is continually increasing due to problems like aging and insufficient concrete production, environmental degradation, neglect, and the requirement for more rigorous design standards [1], Additionally, the repair is required in the event of a visible crack to continue transporting loads and transferring them to the ground [2].The mechanical and durability features can be improved by adding different types of fibers in the right amounts.[3].Due to their advantageous characteristics fiber-reinforced Polymers (FRP) compositions are the most often utilized strengthening options for Reinforced Concrete elements due to factors including their extraordinarily high strength-to-width ratio, rapidity of application, and corrosion resistance [4].where these fibers reinforced polymers (FRP) aimed at intended to improve shear strength in zones with insufficient transverse reinforcement [13].Despite all of these benefits, there are some drawbacks to the FRP strengthening process, most of which are connected to the application of epoxy resins.These disadvantages include high costs, subpar performance in hot environments, applying to moist surfaces is not possible, the FRP separating from the concrete base, etc.To solve the previously mentioned problems, one alternative to the organic binder (usually epoxy) is an inorganic adhesive (cement mortar).As a result, the scientists have created Textile Reinforced Concrete (TRC), a unique material that blends cementitious matrix and cutting-edge textile fabric (with open-mesh arrangement).Technological textiles, which are mostly consisting of Alkali resistant-glass, basalt, Carbon, and aramid textile, have a high level of effectiveness since they are positioned in the principal stress orientation of the combinations [5].This makes it possible to construct concrete parts with very thin structures.In this experimental study, RC beams were strengthened using TRC composites made of textile carbon fiber [6].

Strengthening with Textile Reinforced Concrete (TRC)
A relatively innovative and complex composite material is textile-reinforced concrete.Carbon fiber reinforcement and a cementitious matrix make up the majority of it, while other fiber materials, such as glass that can resist alkalis (AR) glass fiber textiles, may also be applied as reinforcement.Contrary to steel reinforcement, a single AR glass or carbon fiber in a textile can be placed almost anywhere, thus, almost completely adapting to the load's direction of application.Thus, highly efficient reinforcement can be made.The multiaxial fabric serves as the built-in reinforcement for the fabric.A maximum of four layers of fiber textiles in various directions can be stacked on top of one another.As a matrix, high-strength fine-grained concrete with aggregates no larger than 1 mm is employed [6].
Today, upgrading concrete structures with textile reinforcement is a widespread practice.Textiles are composed of long-woven, knotted, or unwoven in two directions of fabric meshes (usually perpendicular).To improve the strength qualities, polymeric additives are used as binders in the mortars in which the textile reinforcement is embedded.Woven or unwoven fabrics are used to reinforce materials with high tensile strengths and minimal elongation characteristics [7].

Types of Textiles
Types of Mesh fabrics that can be used are made of: 1. Mesh basalt fibers textiles (as shown in figure 2a), 2. Mesh carbon fibers textiles (as shown in figure 2b), 3. Mesh Poliparafenil-benzobisoxazole -PBO fibers textiles (as shown in figure 2c), and 4. mesh glass fiber textiles (as shown in figure 2)

Flexural strengthening with TRC
TRC layer-to-tension surface bonding, which would be frequently a beam's soffit, strengthens beams or slabs in flexure.In areas where more moment capacity is required, textile reinforcement is offered.Additionally, a long enough anchorage should be offered.Not every fiber in a textile is used to carry tensile pressures during the strengthening of beams for flexure.The effectiveness of this strengthening technique is debatable because just the fibers parallel to the main axis are pressed in tension in the typical instance of a bidirectional textile (with fiber roving in two perpendicular orientations); the other fibers merely contribute to the formation of the mechanical interlock mechanism.[9].

Failure modes of TRC strengthened beams
The TRC reinforcing system's complicated mechanistic characteristics are shown by the numerous failure mechanisms that have been described in the literature.Schematic representations of all the observed failure modes are shown in (figure 3).In general, an RC element that has had its flexure strengthened using TRM may fail because the strengthening action has been lost [figures 3 (a) through

Previous Experimental Studies
Flexural strengthening beams bonded with TRC have received a lot of interest from most researchers through experimental tests.To better understand how retrofit beams, behave and the various factors that may affect them, numerous tests have been conducted.
Triantafillou. [10] focused on the efficiency of TRC as externally applied bending-enhancing reinforcement in reinforced concrete (RC) beams.Under four-point bending, 3 down-reinforced beams (150 x 250 x 2000 mm) using 2D12 as their main reinforcement were put to the test.Self-compacting concrete with a compressive strength of 28 days of 34.5 MPa was employed for the molding of tested beams.As a control sample, one out of three specimens were utilized for the test (un-strengthened).Whereas the 2nd specimen had 4 layers of textile fabric strengthened with cement-based mortar, the 3rd specimen had 4 layers of reinforcement but was bound with an epoxy resin-based matrix.The specimens were monotonically tested when the load was applied using an actuator while they were placed vertically can and heavily distributed specimens.Two different transducers were put on either side of the beams to measure the deformations at the mid-span.According to the experimental findings, the control specimen had a bilinear response, and the maximum load (83 kN) caused a deflection of over 40 mm.The epoxy-impregnated textile-strengthened beam demonstrated a 50% increase in stiffness and strength.The beam abruptly failed due to the tensile rupture of externally bonded reinforcement at mid-span (at 125 kN).The other beam, which had been reinforced with mortar made of cement, showed nearly identical traits, however, its reaction was a bit more ductile, which implies that steel tends to give at lower load values.The maximum load (111 kN) was even smaller.Debonding toward the bottom of the TRC layer as a result of inter-laminar shearing was the mode of failure.In summary, the TRC-based strengthening has 30 percentage points high efficiencies in terms of ductility but 30 percentage points less efficient in terms of flexural strength (displacement).Si Larbi Amir et al. [11] This study involved the behavior of five 2 m beams that were all four points bent and had the same steel framing (and were therefore shielded from collapse by shearing pressure) (figure 5).They had a compression strength of 30 MPa 2 after 28 days and were all built with the same masonry mixture (mean of 6 beams).The outcomes demonstrate that TRC by itself has a sizable impact and that the load at fracture is significantly higher than for the reference specimen.It is imperative to show how comparable the reference beam's behavior its ductile behavior is.It is conceivable and encouraging, in terms of final behavior, to reinforce beams that are susceptible to bending with connected TRC sheets.Al-Salloum et al. [12] studied the experimentally and numerically, it examined if textile-reinforced mortars (TRCs) are effective at boosting reinforced concrete beams' shear resistance.using concrete that has been pre-mixed and has the required compressive strength of 20 MPa.Eight beams that had their exterior shear capacity increased by TRC layers are tested as part of the experimental program, along with two control beams that were purposefully created to have inadequate shear capacity.The conclusion drawn from experiment results members made of reinforced concrete enhanced that mortar-textile in shear composites significantly increases shear resistance, with the gain increasing with how many layers there are.The greatest rise in shear force is achieved with more layers of cloth with a 45° orientation and cementitious mortar treated with polymers.The tested beams were also subjected to nonlinear finite-element (FE) analysis using the transient nonlinear dynamic analysis program LSDYNA.Case studies for TRC models both with and without mortar were used in the numerical analysis.Particularly with the use of mortar in FE models, there was a good agreement between the outcomes from experiments and computations for the maximum load-bearing capacity.The research was numerically expanded to contain more instances of TRC-enhanced specimens with more TRC layers as well as an instance of an FRP-enhanced specimen.Information about test beams is shown in figure (6).The concrete that had been pre-mixed and had a specific compressive strength of 20 MPa was used to cast the specimens.Four-point loads were used to evaluate six small-scale beams (150 x 200 x 2000 mm) with straightforward supports.Three beams acted as control specimens, three beams underwent TRM using basalt as a textile, and one layer of CFRP laminates was used to strengthen the fifth beam.The specimens were strengthened with 2D10 longitudinal steel bars at the top and 25 mm covers at the bottom.Cementitious materials and cementitious mortar with polymer modifications were employed in the investigation.By using basalt textile-reinforced mortar, the flexural capacity of RC beams was enhanced from 39 percentage points to 91 percentage points.The findings reveal that while increasing flexural strength is where CFRP somewhat outperforms TRM-based strengthening approaches, displacement ductility is where it falls short.Figure (7) Describes in detail about test beams.Verbruggen, et al. [13] focused on the RC beams' tendency to break that have been enhanced using carbon fiber reinforced polymer (CFRP) or textile-reinforced cement (TRC).Out of a total of 17 beam specimens having various types, 3 beam kinds (control, TRC strengthening, or CFRP reinforcement) were used to assess the effect of external reinforcement on the behavior of interior reinforced concrete beams.All of the beams were evaluated with small-scale third-point stress and four-point bending (100 x 100 x 650 mm).All of the beams' major longitudinal reinforcement bars were 2D8.The ready mix compressive strength After 28 days of the concrete has a 33.9 MPa, 33.8 GPa for the young modulus, and 4.8 MPa for the rupture modulus.Figure (8) showed the exterior reinforced beams are put to the test in third-point loading and four-point bending.According to Verbruggen, Tysmans, and 6 Wastiels' experimental findings, adding exterior reinforcement to a concrete beam boosted without affecting the method of collapse, the total number of cracks, or maximum load capacity, the stabilization of the interior reinforcing bars.The quick opening of pre-existing cracks, however, reduces the beam's high initial undamaged rigidity.Escrig et al. [8] studied four various kinds of TRC on RC beams, which are employed as a tensile strengthening system, and are examined till failure.An analysis of their mechanical behavior in comparison to one another reveals that the various TRC configurations used were able to improve their load-bearing capability and alter their method of failure.9 beams were created and constructed for the experimental campaign without tensile reinforcement in two specific places, as illustrated in figure (9).Beams had a cross-sectional area of 300 mm and a length of 1.70 m.On the top and bottom, a total of three longitudinal steel bars measuring 16 mm were inserted, together with five transverse reinforcement stirrups measuring 8 mm.Additionally, new approaches are described that enable assessing TRC's bonding behavior as well as the improvement in flexural toughness.According to the results, all TRC-enhanced specimens achieved better flexural toughness levels than the control beam.These results also point to the importance of adhesion between the concrete and TRC in determining the rupture mechanism and bending toughness of TRC-enhanced specimens.Shah et al. [14] Experimental research is done to determine how well Textile Reinforced Concrete (TRC) works in terms of improving the Flexural and Shear Capability of (RC) Beams.Instead of using epoxy resin as the bonding agent for the textile fabric, a new type of (AR) glass textile fabric was employed as reinforcement since it has advantages related to fire safety and is reasonably priced.One, three, and five strengthening layers as well as the reinforcing arrangement, which consists of bottomand U-shaped casing -are among the factors that were evaluated in this research.In total, 18 (RC) beams (150 × 250 × 1500 mm) were cast and tested under three-point bending till failure as simply supported.Concrete had a 25MPa stated design strength at 28 days.On each face (top and bottom) of the beams, 2-12mm longitudinal rebar was installed at a cover thickness of 25 mm.In terms of Ushape casing, the maximum load carrying capacities of (1, 3, and 5) strengthened layers increased by (42.43, 11.56, and 2.89) percent, as well as by (38.84, 5.38, and 4.14) percent respectively in terms of bottom casing.The findings from the investigation give rise to the possibility of doing additional research to demonstrate the effectiveness of AR-glass TRC for structural strengthening.Figure (10) showed the geometry of the control beam.Jayakrishnan and Shaji.[7] This study involved using textile reinforcement to strengthen concrete constructions.The beam sections employed in this study have dimensions of 150 x 250 mm and a length of 1500 mm.The beam can support 5 tons.The beam will break when 50KN of the force is put on it.The concrete mix used for casting the beam is 25Mpa.The beam is retrofitted with basalt cloth mesh to fix it after a failure.Before applying weight, some beams are retrofitted, and the resistance of the specimen is tested before and after the basalt net.Crack pattern analyses and the determination of flexural strength were both completed.How well different wrapper profiles behave is investigated, and comparisons between maximum displacement and load are made.As a result, the flexural toughness of the reinforced specimens increased noticeably.Figure (11) showed the longitudinal section of the beam.Koutas et al. [9] An up-to-date review of TRC's use in concrete structure strengthening is provided in this publication.First, a description of TRC's tensile and bond characteristics is given.The important parameters are then examined, and a summary of studies on the usage of TRC for retrofitting concrete or RC member's modification for bending, tensile, restriction, and earthquake is included.Bonding TRC layers to the tensile surface, which is commonly the bottom face of a slab or the soffit of a beam figure (12), strengthens beams or slabs in flexure.The tested components in the bulk of the investigations were cylinders made of unreinforced concrete with dimensions of 150 mm in diameter and 300 mm in height.But rectangular column-type elements with sections beginning with 150 mm x 150 mm to 250 mm x 350 mm and heights between 300 and 1,500 mm have also been researched.The experiments mentioned above used AR glass, basalt, aramid, carbon, and PBO fiber fabrics, textiles made of PBO and carbon are the most frequently studied.According to the authors, the use of textile-based composites for earthquake-resistant design and reinforcement of concrete structures has a great promise approach that is gaining more and more attention from the scientific community throughout the world.
Future research in this area should focus on improving the textile reinforcement, understanding how durable the strengthening system is (even in elevated temperatures), and developing design standards within the framework of existing principles for design.Koutas and Papakonstantinou.[15] Explained the result of slurry type on the effectiveness of TRC reinforcement by changing the kind of fabric and the no. of layers of fabric.Nine medium-sized RC beams in total are produced, tested, and found to be under 4-point bending, simply supported.A single beam was used as a control sample and was tested as compact without reinforcing.The remaining packs are initially strengthened using different combinations before being bent repeatedly.parameters being examined Included are: a) the type of mortar (cement-based mortar without polymers) b) (3 versus 6) of reinforcement layers; and c) the kind of fabric (basalt fiber with a small net size vs. fiberglass fabric with a big mesh size).As a result, the flexural capacity caused by TRC strengthening increased and ranged from 7.4% to 37.4% for all strengthened beams.Ponniah and Chidambaram.[16] To prevent growth in cross-section in the tension area of this investigation, the TRM layers were used there.25Mpa of concrete compressive strength is used to make five beam specimens.cementitious matrix makes up the stratum of reinforcement (with and without discontinuous fibers).Four various arrangements of RC beams are tested, also with one control sample for comparison.The tensile face of the beam and the reinforcing layer was from outside joined.Cover concrete was taken out and TRM sections were put in their place to keep the depth of the beam.The proper connection between the old concrete surface and cementitious materials is achieved using a thin coating of epoxy covering.The study's reinforcing method was successful in improving the bending behavior of the RC beams.Figure 14.Details of the geometry and strengthening of RC beams [16].

TRC composite layer
Jie Zhu et al. [17] To strengthen RC beams at the soffit, this study created a textile-reinforced cementitious composite (TRCC) based on MKPC (magnesium potassium phosphate cement).Two reference beams without reinforcement and two reinforced beams underwent three-point bending experiments.The TRCC system shows good adhesion with substrate concrete, according to research observations.Textile grid rupture in TRCC caused the reinforced beams to fail.TRCC has the potential to increase the maximum load by 4-25%, delay the spread of cracks, reduce tensile strain on the primary reinforcement, and decrease deformation at the same load level.Elevated textile rates reduced the ductility of reinforced beams while increasing load resistance.Giese et al. [18] This research aims to investigate the possibility of bending enhancing reinforced concrete beams using a locally made AR fiberglass textile.The specimens underwent a four-point flexure experiment and had dimensions (of 1500 mm long, 200 mm deep, and 120 mm broad).The experimental investigation examines the effects of different textile layers (2, 3, and 4), TRM age (3, 7, and 28 days), and specimen pre-cracking level (no precracking, 50% and 100% of the yielding load) on the bending performance of reinforced RC specimens.The following major findings were made: (a) All specimens showed an increase in max.load and load under serviceability situations.(b) The cracking and yielding loads are affected by various TRM ages and precracking levels, but the max.load is not significantly impacted; (c) As would be expected, the load-carrying capacity rises with the no. of textile layers.

Conclusions
The examination of the wide literature review and the existing body of information can support the following conclusions of the behavior of RC beams reinforcing by TRC provided in this literature: 1.In this literature review, a novel strengthening method (TRC) for shear and flexural strengthening as well as confinement strengthening of reinforced concrete elements is described.The mixture of textiles and cementitious adhesives with polymer modifications is a key component of this technology so it might be used instead of FRP reinforcement.The study's findings demonstrated that TRC jacketing of RC is almost similarly efficient to FRP casing.2. Precracking (initial) stiffness and cracking load increases, post-cracking toughness, and maximum load capability are brought about by adding more TRC layers.In the state of serviceability limit, the flexural resistance also progresses.
12 3.The load capacity rise is in connection with the axial toughness of the textile layers when different fiber types (glass or carbon) are used.4. According to the authors, TRC jacketing is a very promising method for enhancing the capability of reinforced concrete components in terms of attachment, tensile, and bending strength, which is essential for seismic retrofitting and strengthening.The repair of buildings, notably monument-style structures, appears to be a suitable application for this new descent of inorganic binder-based composite materials.Extrapolation of The method to unstrengthen masonry walls produced a notable improvement in strength and deformation resistance.

Figure ( 4 )
Describes in detail the test beam

Figure 8 .
Figure 8.The exterior reinforced beams are put to the test in third-point loading and fourpoint bending [13].

Figure 13 .
Figure 13.Details of the geometry and strengthening of RC beams (all dimensions in mm) [15].

Figure 15 .
Figure 15.Details of the geometry and strengthening of RC beams [17].

Figure 16 .
Figure 16.Details of the geometry and strengthening of RC beams [18].

Table 1 .
Summary of recent research investigation of enhancement RC beams utilizing the TRC strategy.