Textile Reinforced Mortar Composites Research Articles

Application of supervised learning for classification of cracking and non-cracking major damage in TRMs based on AE features

Textile reinforced mortar composites (TRMs) experience various types of damage. In this study, these damage mechanisms (such as cracking and non-cracking) were understood or distinguished with the help of acoustic emissions (AE). Four types of TRMs made of a single mortar matrix and two types of carbon textiles (coated and noncoated) were evaluated under uniaxial tension. Meanwhile, the acoustic emissions were monitored during the tensile test.The study showed that AE features are sensitive to damage evolution but more importantly that TRMs are complex and various modes can coexist. Similarly, the evolution of improved b-value (Ib) also demonstrated sensitivity to the existence of damage. Finally, the supervised learning models (trained on AE data) demonstrated that information on the instant of cracking obtained through digital image correlation (DIC) can be successfully coupled with AE features to separate the cracking and non-cracking damage types with accuracy of above 80 %.

Optimizing Epoxy Interfacial Bonding Properties and Failure Mechanism between Carbon Textile-Reinforced Mortar Composites and Concrete Substrates.

Textile-reinforced mortar (TRM) composites have been extensively utilized in building reinforcement due to their exceptional mechanical properties. The weakest link in the entire structure is the interface between the TRM composites and the concrete; however, it plays a crucial role in effectively transferring stress. Researchers have taken measures to improve the strength of the interface, but the results are relatively scattered. In this paper, the surface treatment of the substrate, the thickness of the surfactant, and the physical doping of the surfactant on the interfacial bonding strength of the concrete were comparatively studied. The results demonstrate that the sandblasting treatment on the surface of the concrete enhances the bonding area between the mortar and the concrete of the reinforcement layer, leading to a 50% increase in the bending resistance of the structure. When the surfactant thickness increases to 0.5 kg/m2, more surfactants penetrate the mortar and concrete. This significantly inhibits the occurrence of cracks in the structure. The addition of 2.5% Al2O3 nanomaterials to the surfactant diminishes the shrinkage rate of the curing process, enhances the impact toughness, and improves the flexural and compressive properties of the bonding layer. The ultimate load of the structure increases by 65%. Physical doping of the surfactant is the most effective measure with the most apparent improvement result. It significantly enhances the bonding strength of the interface and can be widely used in construction.

Experimental and analytical investigation of the tensile mechanism of textile-reinforced mortar (TRM) composites and fabric grids in elevated temperatures

The textile-reinforced mortar (TRM) combines high-strength fabric textiles with cementitious mortar matrix to enhance mechanical behaviour and durability, especially at high temperatures. The current study investigated how basalt, carbon, and glass textile grids and TRM composites respond under direct tensile and thermal loading up to 800 ℃. Changes in microstructure were analyzed using scan electron microscopy (SEM), thermo-gravimetric analysis (TGA), and ultrasonic pulse velocity (UPV). The results indicated that temperature significantly affected the coating material and cementitious mortar, weakening the grids and composite specimens. Carbon and glass fibre grids proved more resilient, and the carbon and glass TRM reduced 50% of their ultimate stress at 500 ℃, while for basalt TRM is 200 ℃. A slight gain of strength was observed for all TRM specimens at 300 ℃, and SEM analysis revealed critical changes in the mortar matrix and interfacial transition region. The results were further utilized to calibrate the Gibson model considering humidity and early-stage coating material changes, and yielding results consistent with experimental data.

Influence of PLA impregnation on the performances of vegetable fibers for lime-based composites

In recent years, the application of inorganic lime-based Textile Reinforced Mortar (TRM) for repairing existing masonry structures has gained a relevant interest due to the strong compatibility between masonry elements and the strengthening composite. In addition, several research groups worldwide have recently focused on the possible use of natural fibers for replacing the traditional reinforcement (e.g., steel, fiberglass, basalt, PBO, aramid, carbon, etc.) generally employed for TRM composites. As a matter of fact, the natural fabrics (easily available and biodegradable) present comparable resistance to conventional fabrics, good compatibility with the lime-based mortars and elastic modules compatible with masonry elements. On the other hand, it has been also demonstrated that one of the most relevant aspects on their possible application is related their long-term and durability performances which can be mitigated with coating and impregnation treatments. In this context, the present paper presents the preliminary result of an experimental research aimed at investigating the influence of a biodegradable coating system (PLA - polylactic acid) applied to different types of natural fibers (made of flax and jute) on the resulting performances either from the physical and mechanical standpoint. The results demonstrate a significant improvement of the observed performance of natural fibers that can be more properly employed for the production of natural TRM composites.

Flexural strengthening of reinforced concrete beams using textile-reinforced mortar improved with short PVA fibers

Textile-reinforced mortar (TRM) composites were developed to avoid the problems caused by fiber-reinforced polymer (FRP) composites. Furthermore, short and dispersible polyvinyl alcohol (PVA) fibers were applied in TRM matrix to improve the brittle behavior and limit the crack width of TRM composites. In this study, eight reinforced concrete (RC) beams, including two reference beams and six strengthened beams, were designed to investigate the flexural behaviors of RC beams strengthened with PVA fibers-improved TRM composites. The investigation variables were (i) the longitudinal steel bar ratio, (ii) the carbon textile reinforcement ratio, and (iii) the sustaining load level. The test results indicated that (1) TRM composites could effectively limit the crack width of RC beams, and multi-crack behavior was observed in the strengthening overlay. (2) The flexural capacity of strengthened beams was enhanced as the number of textile layers increased. This enhancement came with a decrease in deformation, energy absorption, and ductility to some extent depending on the failure modes. (3) For strengthened RC beams with the sustaining load of 60kN and 96kN, the yield load was decreased by 8% and 16% respectively compared with the strengthened beam without the sustaining load. The enhancement efficiency in yield load was reduced as the sustaining load level increased. However, an acceptable reduction in ductility was obtained. Finally, based on the plane section assumption, an analytical mode was proposed to calculate the flexural capacity and deflection of RC beams strengthened with TRM composites.

Design of Strain-Hardening Natural TRM Composites: Current Challenges and Future Research Paths

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed.

Research on mechanical properties and failure mechanism of TRM composites via digital image correlation method and finite element simulation

The purpose of this paper is to study tensile properties and interfacial bonding properties of textile reinforced mortar composites (TRM) widely used for externally strengthening damaged buildings. Based on the digital image correlation (DIC) method and finite element (FE) simulation, the tensile and interfacial shear test results of steel fiber textile and carbon fiber textile reinforced mortar composites were analyzed. First, DIC was used to detect the crack onset and propagation of the specimen during the tensile process. The concept of gradient interface was introduced to improve the bonding performance. The effects of the hydration degree of mortar, and reinforcing textile type on interfacial bonding properties were then evaluated through double-lap shear testing. Last, the stress distribution and load transfer during textile pull-out from the mortar were analyzed based on FE simulation with the bond-slip law extracted from the double-lap shear experiment.

Flexural response of TRM subjected to low-velocity impact loads: Experimental and analytical study

A constitutive approach to investigate the flexural impact performance of textile-reinforced mortar (TRM) is presented in this study. Experiments were performed under three-point bending conditions on a drop-weight impact system at 1, 2, 3, 4, and 4.5 m/s. Experimental results showed that the differences in peak load from 4.5 to 1 m/s were 1.964 kN (for BTRM-4) and 2.191 kN (for BTRM-6), and in energy absorption from 4.5 m/s to 1 m/s incident velocities were 2.66 J (for BTRM-4) and 2.98 J (for BTRM-6). Additionally, analytical modeling of experimental results was performed to identify the correlation between the experimental and analytical results. The parameters for a strain-hardening material model were obtained by using closed-form equations. The prepared model could reproduce a tripartite load-displacement response related to pre-cracking and post-cracking behavior. The results also verified that the best agreement between the analytical model and experimental data was achieved by considering scattering, softening, and reinforcement waviness in cement matrix under different loadings. The tensile properties of the tested samples were predicted by using an inverse algorithm and model parameters. Notably, the parametric model overpredicted the simulated three stages of TRM composites. Results could be used as average load values in the structural design and analysis of cement-based material composites under different impact loads.

Tensile characteristics of carbon textile-reinforced mortar incorporating short amorphous metallic and nylon fibers under designed environmental conditions

This study experimentally investigated the mechanical tensile properties of carbon textile-reinforced mortar (TRM) composites utilizing amorphous metallic and nylon short fibers with lengths of 15 and 12 mm, respectively, at 0.4 % and 0.7 % fiber content under the designed conditions. The conditions of the ambient control, water immersion, sulfate immersion, and wet-dry cycle sulfate attack were designed to investigate the tensile characteristics of the TRM composite and the effectiveness of applying short fibers under normal and harsh environments accelerated using a temperature and humidity machine. The experiments included tensile tests for dried carbon textiles, water absorption tests for mortar matrices with and without short fibers, external damage inspection for TRM specimens and compressive tests for mortar matrices after exposure to the designed conditions. Furthermore, based on RILEM TC 232-TDT, tensile tests of 60 TRM specimens were performed after exposure to the designed conditions. The results indicate that the existence of both amorphous metallic and nylon short fibers significantly improves the TRM tensile properties under all conditions, in which the amorphous metallic fiber was found to be more effective at low strain levels, whereas the positive effect generated by nylon fibers only considerably appeared at high strain values. In addition, a positive effect was observed under the prolonged water immersion condition. Besides, the TRM specimens without short fibers were severely damaged under the designed sulfate attack, and utilizing them could prevent the propagation of the damage, in which applying 0.4 % nylon fibers proved to provide the highest resistance capability.

Tensile Behavior of Textile-Reinforced Mortar: Influence of the Number of Layers and their Arrangement

In the last decade, textile-reinforced mortar (TRM) composites have been introduced as a sustainable solution for the strengthening of masonry structures. As an externally bonded reinforcement system, it consists of textile fibers embedded in an inorganic matrix (e.g., lime or cement mortar) applied to the substrate. Even though many studies have been focused on characterizing the mechanical behavior of TRM composites in recent years, there are still some drawbacks, including their tensile performance and few studies about multilayer textiles arrangement. This work aims at clarifying the effect of adding a second textile layer to TRM composites and investigating how textile arrangement affects the tensile behavior of the composite system. For this purpose, AR-glass and steel-based TRM composites were used in single layer and multilayer with different arrangements embedded in a lime-based mortar. The results show that using two plies of textile mesh improves the tensile response of TRM composites. In addition, it is found that the arrangement of different layers in the matrix influences the TRM response in different stress stages. The addition of a thin layer of mortar between two layers seems to improve the stiffness in uncracked condition and slightly decreases the final strength of TRM. Thus, the present study makes a step toward optimizing the arrangement of textiles in multilayer TRM composites.

Cyclic Load Effects on the Bond Behavior of Textile Reinforced Mortar (TRM) Composites

There has been considerable attention drawn to the application of textile reinforced mortar (TRM) composites for strengthening existing masonry and concrete structures. These composites are made from textile fibers embedded in an inorganic matrix and act as externally bonded reinforcement (EBR). Therefore, a careful observation must be made of the bond of the mortar to the substrate and the bond of the mortar to the textile. Despite numerous studies of the bond behavior of TRM composites conducted in recent years, no constitutive bond behavior law under cyclic loading has been determined. In most available studies, the most common method of testing TRM-to-substrate bonds is the single-lap shear test. Contrary to that, the bond performance of fibers to mortar has received little attention and has been the subject of this study. This paper describes a laboratory study investigating the textile's interfacial bond behavior to the mortar fiber under cyclic loading. It was shown that cycling can cause a loss in strength, which varies with the number of cycles.

Experimental Investigation on the Bond Behaviour of Masonry Element Strengthened with Carbon-TRM and Steel-TRM

Textile reinforced mortar (TRM) composites are an innovative solution for strengthening existing structures. TRM composites are produced with high-strength textile embedded in inorganic mortar matrices, demonstrating compatibility with existing masonry. As TRM is externally bonded to the surface of the structure, the bond behaviour between TRM and masonry substrate is a critical issue to investigate. In this study, experimental research aims to deeply understand the bond behaviour of TRMs for strengthening masonry structures. The experiments mainly consist of a series of single-lap shear bond tests on TRMs to masonry substrates. Two types of textiles (carbon and steel textile) combined with two mortar matrices (cement and lime-based mortar) were used to construct TRM. The effect of the textile and mortar matrix is presented. The test results are discussed in terms of the full range of load-slip responses and failure modes. The result showed that TRM with steel textile and cement-based mortar matrix offers better bond behaviour, but the risk of masonry damage should also be considered.

Characterization of Application Methods for Textile-Based Composite Structures in Coastal Environments

Park, J.; You, J.; Park, S.-K.; Ryu, S.-C., and Hong, S., 2021. Characterization of application methods for textile-based composite structures in coastal environments. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 131-135. Coconut Creek (Florida), ISSN 0749-0208. Textiles exhibit many advantages including high strength/weight ratio and high corrosion resistance. Therefore, textiles can substitute steels in textile-reinforced concrete (TRC) and can strengthen existing RC structures, such as textile-reinforced mortar (TRM), in coastal environments. However, there is a difference in the structural performance of TRC and TRM so that it is important to clearly distinguish the behavior of textile-based composites. In this study, the flexural performance, serviceability, ductility, and fabrication process of TRC and TRM were analyzed and compared via two separate application. The results of the experiments were expressed as indexes, which were compared with that of the reference RC specimen. Finally, an efficient method for applying textile-based composite structures in a coastal environment was considered in terms of flexural strength, serviceability, ductility, and fabrication process. The TRM composite exhibited unstable behavior after the yield stage. The TRC composite exhibited stable behavior in all the loading stages and showed higher ductility than that of the TRM composites. The results of this study are expected to aid in the selection of an appropriate application method for conducting intensive durability verification.

Cyclic behavioral characteristics of RC beams strengthened by U-wrapped TRM jacket with anchorage details

In this study, we investigated the seismic performance of reinforced concrete (RC) beams strengthened by a U-wrapped textile-reinforced mortar (TRM) jacket with and without incorporating anchorage details. Ten full-scale single-curvature RC beams were fabricated and tested under cyclic loading. The main test parameters included longitudinal reinforcement ratio, textile reinforcement ratio adopted in the TRM composite, and anchorage details applied to the U-wrapped TRM jacket. In the present study, a near-surface mounted (NSM) anchorage method with steel rebars was newly proposed to enhance the effectiveness of the TRM jacket. The experimental results indicated that the NSM anchorage detail was beneficial in preventing the debonding of the TRM jacket from the concrete substrates under cyclic loading conditions. Consequently, the specimens retrofitted with anchored jackets showed an improvement in terms of load-carrying and deformation capacity, stiffness degradation, and energy dissipation capacity compared to the non-anchored test specimens. In addition, an analytical model was proposed to predict the inelastic deformation capacity of RC beams strengthened with a U-wrapped TRM jacket based on the failure mechanism of the concrete compression zone after flexural yielding, and its prediction showed reasonable agreement with the experimental results.

Flexural strengthening of RC slabs using textile reinforced mortar improved with short PVA fibers

Textile reinforced mortar (TRM) composite is a viable and effective solution for fiber reinforced polymer (FRP) in some limited environments. Short and dispersible polyvinyl alcohol (PVA) fibers were applied in TRM matrix to remedy the lack of cracking strength of TRM composite, which was conducive to improve the cracking capacity and serviceability of flexural members. The effects of the matrix improved with and without short fibers and the reinforcing ratio of textiles on the flexural behavior of reinforced concrete (RC) slabs were studied in this work. Six RC slabs were fabricated and tested under four-point flexural loading, including one control slab, one with one layer of carbon TRM composite without short fibers, one with a matrix improved by short fibers and three with carbon TRM composite improved with short fibers. The results showed that short PVA fibers could increase the cracking capacity of RC slabs by 90 ~ 105%. The flexural capacity of strengthened slabs was increased with the increasing of reinforcing ratio of textiles. Based on the strain compatibility and force equilibrium, an analytical model was given. Moreover, the model was further improved according to the predicted formula of tensile strength for TRM. The theoretical and experimental results showed a very good agreement.

Diagonal compressive behavior of unreinforced masonry walls strengthened with textile reinforced mortar added with short PVA fibers

Textile reinforced mortar (TRM) has been intensively researched over at last two decades. It is a composite consisting of textiles and inorganic matrix. The study presents an investigation on the diagonal compressive performances of unreinforced masonry (URM) walls strengthened with carbon and glass TRM composites which are added with short and water-dispersible polyvinyl alcohol (PVA) fibers. Ten specimens were designed to study the effect of the reinforcement configuration (single/double sides), layers of textiles and types of textiles on the in-plane behaviors of masonry walls under diagonal compression tests. It included a reference specimen, four single-side strengthened specimens and five double-side strengthened specimens. The failure mode, shear stress–strain response and deformation capacity of specimens were presented and discussed in this paper. The results showed that the improved TRM composites could improve the deformation and bearing capacity of masonry walls. The bearing capacity was predicted based on different failure modes of specimens. Furthermore, two non-dimensional parameters (α and β) were proposed to compare the efficiency and enhancement ratio of different TRM composites reported in literatures and this paper. It indicated that the improved TRM composites reached a considerable efficiency in improving the bearing capacity.

Slip rate effects and cyclic behaviour of textile-to-matrix bond in textile reinforced mortar composites

The structural effectiveness of textile reinforced mortar (TRM) composites relies on their load transfer capacity to the substrate and the interaction between textile and mortar. The bond plays a crucial role in mechanism of TRM composites. Despite some recent investigations, a deep understanding still needs to be gained on the textile-to-mortar bond to develop suitable analytical and numerical predictive models, improve test methods, and orient design criteria. This work describes a laboratory study in which pull-out tests were carried out to investigate the effect of the slip rate and cyclic loading on the textile-to-mortar bond behaviour. Alkali-resistant glass fabric and sgalvanised ultra-high tensile strength steel cords embedded in two different lime-based mortars were tested. The pull-out response was sensitive to the strain rate at low rates. Cyclic loading produced a strength degradation, which reduced with the number of cycles.

Flexural Strengthening of Two-Way RC Slabs with Cut Openings Using Textile-Reinforced Mortar Composites

Abstract This paper presents an experimental investigation on the application of textile-reinforced mortar (TRM) layers as a means of increasing the flexural capacity of two-way reinforced concrete...

Mechanical Response and Analysis of Cracking Process in Hybrid TRM Composites with Flax Textile and Curauá Fibres.

In recent years, the use of plant fibres in Textile-Reinforced Mortar (TRM) composites emerged as a valuable solution to increase their sustainability. Several studies carried out to mechanically characterize the so-called Natural TRMs, although showing promising results, also emphasised some drawbacks due to a severe deformability of the system and to durability issues. This study aims at improving the mechanical behaviour of Natural TRMs including impregnated flax textile (Flax TRMs) by the addition of short curauá fibres within the matrix. Flax TRM specimens were tested in tension to assess the influence of the fibre-reinforced mortar on the composite response. The crack pattern developed during the test was investigated via Digital Image Correlation analysis and by means of an analytical simplified model proposed by the authors. The addition of curauá fibres resulted in a denser crack pattern and in a significant decrease of the mean crack width (around 20%). The overall tensile response of Flax TRMs including curauá fibres resulted closer to the ideal three-linear behaviour of strain-hardening TRM composites with respect to the conventional Flax TRMs by also presenting an increase of dissipated energy of around 45%. This study paves the way for further analysis aimed at enhancing the mechanical performance of Natural TRMs adopting sustainable improvement techniques.

Textile-to-mortar bond behavior: An analytical study

Reliable design and application of textile-reinforced mortar (TRM) composites for the repair of existing masonry and concrete structures requires a fundamental understanding of the textile-to-mortar bond behavior as one of the main mechanisms controlling their nonlinear response and cracking behavior. Suitable test setups and analytical models are needed to extract the bond-slip laws from the experimental pull-out tests. This paper proposes a new bond-slip law and analytical model, which predicts the bond behavior of lime and cement-based TRM composites considering the slip hardening and softening effects observed in experimental tests. For this purpose, the pull-out response of experimental specimens with different fiber types (steel and glass), bond lengths, and mortar age are analyzed, and their bond slip-laws are extracted. The accuracy of the developed model is shown by comparing analytical and experimental results.