Textile-reinforced Mortar Jacketing Research Articles

Local Strengthening of Reinforced Concrete Frames Using Textile Reinforced Mortar Jackets under Gravity and Cyclic Loadings

Local Strengthening of Reinforced Concrete Frames Using Textile Reinforced Mortar Jackets under Gravity and Cyclic Loadings

Failure Mode Prediction of Unreinforced Masonry (URM) Walls Retrofitted with Cementitious Textile Reinforced Mortar (TRM)

The brittle failure of unreinforced masonry (URM) walls when subjected to in-plane loads present low shear strength remains a critical issue. The investigation presented in this paper touches on the retrofitting of URM structures with textile-reinforced mortar (TRM), which enables shifting the shear failure mode from a brittle to a pseudo-ductile mode. Despite many guidelines for applying composite materials for retrofitting and predicting the performance of strengthened structures, the application of TRM systems in masonry walls is not extensively described. A thorough retrospect of the literature is presented, containing research results relating to different masonry walls, e.g., bricks, cement, and stone blocks strengthened with TRM jackets and subjected to diagonal compression loads. The critical issue of this study is the failure mode of the retrofitted masonry walls. Available prediction models are presented, and their predictions are compared to the experimental results based on their failure modes. The novelty of this study is the more accurate failure mode prediction of reinforced masonry with TRM and also of the shear strength with the proposed model, Thomoglou et al., 2020, at an optimal level compared to existing regulations and models. The novel prediction model estimates the shear failure mode of the strengthened wall while considering the contribution of all components, e.g., block, render mortar, strengthening textile, and cementitious matrix, by modifying the expressions of the Eurocode 8 provisions. The results have shown that the proposed model presents an optimum accuracy in predicting the failure mode of all different masonry walls strengthened with various TRM jackets and could be taken into account in the regulations for reliable forecasting.

Finite-Element Analysis of Wall-Like RC Columns Strengthened with FRP and TRM Jackets under Concentric and Eccentric Loadings

The present paper shows the results of nonlinear finite-element analysis (FEA) of fiber-reinforced polymer (FRP) and textile-reinforced mortar (TRM) confined reinforced concrete (RC) wall-like columns under concentric and eccentric axial loads. The FEA column models were validated with an experimental study in the literature. A parametric study was performed on the validated models to examine the effectiveness of FRP versus TRM considering various columns’ cross section aspect ratios, number of layers, and eccentricities. In addition, interaction diagrams were constructed for the control and strengthened columns. Good agreement was achieved between the experimental and validated FEA results. The parametric study results showed that, as compared to TRM, FRP jackets were more effective in terms of axial strength improvement. This effectiveness was less pronounced in columns with higher aspect ratios. Furthermore, the effectiveness of both systems was distinct when three layers were applied with 45% and 39% enhancements in the axial strength as compared to the control model, respectively. Furthermore, the axial strength of all columns reduced with higher eccentricity values. As the eccentricity increased, the axial capacity of the models strengthened with FRP converged with the control ones. In general, the TRM-confined model’s interaction diagram was superior to that of its FRP-confined counterparts.

Finite Element Analysis of Axially Loaded RC Walls with Openings Strengthened Using Textile Reinforced Mortar for Sustainable Structures

Sustainable solutions in the building construction industry promotes the use of innovative materials such as textile reinforced mortar (TRM) as a strengthening technique resulting in a reduced life-cycle cost. This paper presents a nonlinear finite element analysis (FEA) of TRM strengthened RC walls with cut-out openings under axial loading. FEA models were developed and validated with two experimental tests from the literature. Subsequently, a parametric study was performed to investigate the contribution of TRM in strengthening RC walls considering various opening sizes, types, numbers and orientations of window openings, and TRM strengthening configurations. The parametric study results revealed that strengthened models with smaller opening sizes had higher axial strength enhancement. Furthermore, the increase in the axial load capacities of walls with door and window openings were 34 and 26%, respectively, as compared to the corresponding control ones. TRM was more effective with a lower opening aspect ratio (Ho/Lo). In addition, confining the wall piers with U-shaped TRM jackets was the most effective configuration in improving the walls’ axial strengths with maximum enhancements of 16 and 22% as compared to the models strengthened with side-bonded sheets and strips, respectively. Finally, the axial strengths of the FEA models were also compared with the existing empirical solution and showed reasonable correlation with an average discrepancy of 15%.

Mechanical Properties of Rubberised Concrete Confined with Basalt-Fibre Textile-Reinforced Mortar Jackets

This paper presents an experimental investigation of the mechanical properties of rubberised concrete confined with basalt-fibre textile-reinforced mortar (TRM) jackets. The main aim is to evaluate the effectiveness of the TRM confinement scheme on cylindrical rubberised concrete specimens by examining five different mixtures (rubber content ranging from 10.5% up to 42% of the total aggregate volume), including a plain concrete reference mixture. Unconfined and confined specimens with either one or two TRM layers were subjected to monotonic axial loading. The results indicate a decrease in the compressive strength of unconfined concrete as the rubber content increased. The stress–strain curves of rubberised concrete became smoother at the peak as the rubber content increased, also exhibiting increased axial strain capacity post-peak. Rubberised concrete exhibited less brittle failure than plain concrete, accompanied by increased lateral dilation. Confinement with TRM increased the compressive strength, while also enhanced the performance in terms of toughness and axial deformation capacity compared to unconfined concrete. Overall, it is concluded that there is a promising potential for using TRM-confined rubberised concrete in applications with ductility demands and low environmental footprint specifications.

Lateral Deformation Capacity and Plastic Hinge Length of RC Columns Confined with Textile Reinforced Mortar Jackets

This paper presents a nonlinear finite element analysis (FEA) of textiles reinforced mortars (TRM)-confined reinforced concrete (RC) columns through jacketing, under combined axial and cyclic loadings. The FEA models were validated with an experimental study in the literature that was conducted on full-scale square columns reinforced with continuous steel bars (no lap splices). Subsequently, parametric study was performed on the validated FEA models. The parameters considered include various jacket’s lengths and mortar strengths. Moreover, semiempirical models were developed to evaluate the plastic hinge length (LP) and the ultimate drift ratio of RC columns confined with TRM and FRP jackets, while considering the jacket length effect. The FEA models and experimental results were in good agreement. The finite element results revealed that the increase in the jacket length improved the lateral deformation capacity and increased the plastic hinge length linearly up to a confinement ratio of 0.2. Beyond this point, the plastic hinge length shortened as the confinement ratio raised. Moreover, mortars with higher flexural strength resulted in a slightly higher deformation capacity. However, the difference in the mortar compressive strength did not affect the ultimate lateral deformation capacity. The semiempirical models show that the average difference in the predicted LP and the ultimate drift ratio values as compared to the experimental and simulated columns was 3.19 and 16.06%, respectively.

Integrated Seismic and Energy Retrofitting System for Masonry Walls Using Textile-Reinforced Mortars Combined with Thermal Insulation: Experimental, Analytical, and Numerical Study

Taking into consideration the seismic vulnerability of older buildings and the increasing need for reducing their carbon footprint and energy consumption, the application of an innovative system is investigated; the system is based on the use of textile-reinforced mortar (TRM) and thermal insulation as a means of combined seismic and energy retrofitting of existing masonry walls. Medium-scale tests were carried out on masonry walls subjected to out-of-plane cyclic loading. The following parameters were investigated experimentally: placement of the TRM in a sandwich form (over and under the insulation) or outside the insulation, one-sided or two-sided TRM jacketing and/or insulation, and the displacement amplitude of the loading cycles. A simple analytical method is developed and found in good agreement with the test results. Additionally, numerical modeling is carried out and also found in good agreement with the test results. From the results obtained in this study, the authors believe that TRM jacketing may be combined effectively with thermal insulation, increasing the overall strength and energy efficiency of the masonry panels in buildings.

Mechanical characteristics of brick masonry using natural fiber composites

Unreinforced masonry (URM) is brittle and most vulnerable to damage in the event of earthquake. The failure of masonry walls during earthquakes lead to the development of new techniques for strengthening. In this context, Fiber reinforced polymer (FRP) materials are evolving to retrofit/strengthen both concrete and masonry structures. A novel composite material called textile reinforced mortar (TRM) also known as fiber reinforced cementitious matrix (FRCM) has been introduced by researchers to alleviate the problems arising from the use of fiber reinforced polymers. The present study is hence focused on comparing the mechanical characteristics of brick masonry using two different strengthening systems (TRM versus FRP). Towards this aim, compressive and flexural strength of brick masonry prisms with FRP and TRM jacketing was evaluated. Inorganic cement based mortar such as Cement granite fines paste with jute textile was used in this work. The experimental results indicated that FRP is more effective compared to TRM and the effectiveness ratio of the two systems is 1.13 and 1.06 for F1 fiber, 1.34 and 1.14 for F2 fiber for compression test on English bond prisms. Significant difference in performance of both the composites was observed in case of flexural strength conducted on brick masonry prisms.

Experimental study on the seismic performance of RC columns retrofitted by lap-spliced textile-reinforced mortar jackets after high-temperature exposure

The present experimental study investigated the seismic performance of reinforced concrete columns retrofitted by lap-spliced TRM jackets after high-temperature exposure. A total of eight column specimens were fabricated and tested, with the two main parameters being the amount of carbon fiber mesh, and the surface treatment method in lap-sliced regions. High-temperature tests were performed in a furnace chamber with moderate temperature up to 250 °C, followed by ultrasonic image scanning and cyclic loading tests. The experimental results from ultrasonic image scanning and cyclic loading tests illustrate that even after exposure to high temperature, the retrofitted solution using TRM jackets with the proposed lap-spliced details was effective, in terms of increasing both the strength and the deformation capacity. In addition, an analytical model to evaluate idealized backbone curves used for nonlinear analysis of columns retrofitted by TRM jackets subjected to high temperatures was proposed and showed reasonable agreement with the experimental results.

Confinement of masonry columns with textile-reinforced mortar jackets

This paper presents an experimental investigation on the confinement of masonry columns with textile-reinforced mortar (TRM) jackets as a means of enhancing their axial load-carrying capacity and axial deformability. The experimental program included the construction and testing of twenty-six masonry prisms, which were subjected to monotonic concentric compression. The specimens were equally divided in two testing Series based on their cross-section geometry; square and rectangular with 2:1 aspect ratio. One specimen from each Series was tested unconfined and served as reference specimen, whereas the rest twelve specimens were tested after receiving TRM jacketing. Apart from the cross-section geometry, the investigated parameters included the textile material (two types of carbon-fibre textiles, one glass and one basalt-fibre textile), and the amount of the textile reinforcement (no. of layers). Overall, TRM confinement of masonry columns increased both their compressive strength and ultimate axial strain, with effectiveness factors varying between 1.02 and 1.61 for the strength and from 1.05 to 4.11 for the strain. The effect of the investigated parameters is carefully examined and discussed in the paper, in terms of both the compressive strength and the ultimate axial strain enhancement. Modelling of masonry confined with TRM jackets is presented by adopting a widely accepted confinement model, properly calibrated with the test results to account for the behaviour of the TRM confined masonry. From the results obtained in this study, it is believed that TRM jacketing is a promising solution for the confinement of masonry columns.

Concrete confinement with TRM versus FRP jackets at elevated temperatures

Despite the clear cost, ease of installation, and construction schedule advantages of confinement of concrete structural elements with fibre-reinforced polymers (FRPs) for strength and deformability enhancement, concerns as to their performance at elevated temperature, or in fire, remain. The results of a series of elevated temperature experiments on FRP and textile reinforced mortar (TRM) strengthening systems for confinement of circular concrete columns are presented. The behaviour and effectiveness of the respective confining systems is studied up to temperatures of 400 °C. A total of 24 concrete cylinders were wrapped in the hoop direction with different amounts of FRP or TRM, heated to steady-state temperatures between 20 and 400 °C, and loaded to failure in concentric axial compression under a steady-state thermal regime. The results indicate that the effectiveness of the FRP confining system bonded with epoxy decreased considerably, but did not vanish, with increasing temperatures, in particular within the region of the glass transition temperature of the epoxy resin/adhesive. Conversely, the TRM confining system, bonded with inorganic mortar rather than epoxy, demonstrated superior performance than the FRP confining system at 400 °C as compared against tests performed at ambient temperature.

Seismic performance of reinforced concrete columns retrofitted by textile-reinforced mortar jackets

This study developed a practical retrofit solution for reinforced concrete (RC) columns using textile-reinforced mortar jackets. The main test parameters of this study include the number of textile layers, and the surface treatment methods in lap-spliced regions. The experimental results indicated that the retrofitted solutions by textile-reinforced mortar (TRM) jackets with the proposed details in the lap-spliced regions were quite effective as a means of increasing both the strength and deformation capacity. Moreover, an idealised backbone model to evaluate modelling parameters for the nonlinear analysis of RC columns retrofitted with TRM jackets was constructed, and it showed reasonable agreement with the test results.

Combined seismic and energy upgrading of existing reinforced concrete buildings using TRM jacketing and thermal insulation

The concept of the combined seismic and energy retrofitting of existing reinforced concrete (RC) buildings was examined in this paper through a number of case studies conducted on model buildings (simulating buildings of the „60s-‟80s in southern Europe) constructed according to outdated design standards. Specifically, seismic and thermal analyses have been conducted prior to and after the application of selected retrofitting schemes, in order to quantify the positive effect that retrofitting could provide to RC buildings both in terms of their structural and energy performance. Advanced materials, namely the textile reinforced mortars (TRM), were used for providing seismic retrofitting by means of jacketing of masonry infills in RC frames. Moreover, following the application of the TRM jackets, thermal insulation materials were simultaneously provided to the RC building envelope, exploiting the fresh mortar used to bind the TRM jackets. In addition to the externally applied insulation material, all the fenestration elements (windows and doors) were replaced with new high energy efficiency ones. Afterwards, an economic measure, namely the expected annual loss (EAL) was used to evaluate the efficiency of each retrofitting method, but also to assess whether the combined seismic and energy retrofitting is economically feasible. From the results of this preliminary study, it was concluded that the selected seismic retrofitting technique can indeed enhance significantly the structural behaviour of an existing RC building and lower its EAL related to earthquake risks. Finally, it was found that the combined seismic and energy upgrading is economically more efficient than a sole energy or seismic retrofitting scenario for seismic areas of south Europe.

Out-of-Plane Strengthening of Masonry-Infilled RC Frames with Textile-Reinforced Mortar Jackets

AbstractThis paper presents an experimental investigation on the use of textile-reinforced mortar (TRM) jackets as a means of improving the out-of-plane performance of masonry infill walls in reinf...

On the design of shear-strengthened RC members through the use of textile reinforced mortar overlays

Abstract Textile reinforced mortar (TRM) is a promising alternative to the FRP retrofitting solution for shear strengthening of reinforced concrete (RC) beams, based on the experimental results presented so far in the literature. Thus, the development of reliable and accurate design models for shear strengthening of concrete members with TRM is required for enabling their wider use in real applications. The available experimental data in the literature are limited and in most cases, a detailed description of the failure modes observed in the TRM jackets and information related to the characteristics of the textile material and the mortar strength are missing, complicating the development of design guidelines. In this paper, a design model to calculate the contribution of the TRM jacket to the total shear resistance was developed using all the well reported available data that were grouped based on the observed failure modes. Specifically, local damage of the jacket including slippage of the fibres through the mortar constitutes a recurring failure mode in concrete beams strengthened in shear with TRM jackets, apart from debonding of the jacket from the concrete substrate including peeling-off of the concrete cover or fracture of TRM jacketing that are also observed in case of fibre reinforced polymer (FRP) jacketing. The key parameters affecting each failure mode were defined and design formulations to calculate the contribution of the TRM jacket to the total shear resistance of RC beams for each failure mode were suggested, whereas a criterion indicating when each failure mode is possible to be observed was also set for using the proper formulation for each TRM system.

Shear strengthening of concrete members with TRM jackets: Effect of shear span-to-depth ratio, material and amount of external reinforcement

Abstract An experimental work on reinforced concrete (RC) rectangular beams strengthened in shear with textile reinforced mortar (TRM) jackets is presented in this paper, with focus on the following investigated parameters: (a) the amount of external TRM reinforcement ratio, ρf, by means of using different number of textile layers and different types of textile fibre materials (carbon, glass, basalt); (b) the textile geometry, and (c) the shear span-to-depth ratio, a/d. In total, 22 tests were conducted on simply supported rectangular RC beams under (three-point bending) monotonic loading. The experimental results revealed that: (1) TRM is very effective when the failure is attributed to debonding of the TRM jacket from the concrete substrate; (2) the trend of effective strains for carbon, glass and basalt TRM jackets is descending for increasing values of the TRM reinforcement ratio, ρf, when failure is associated to debonding of the jacket; (3) the effect of textile geometry is significant only for low values of ρf, resulting in variances in the capacity enhancement and the failure modes, and (4) the shear span-to-depth ratio has practically no effect to the failure mode nor to the TRM jacket contribution to the total shear resistance of the RC beams.

An innovative structural and energy retrofitting system for URM walls using textile reinforced mortars combined with thermal insulation: Mechanical and fire behavior

The application of a new system, which combines textile reinforced mortars (TRM) and thermal insulating materials as a means of both structural (including seismic) and energy retrofitting of masonry walls is experimentally investigated in this study. Medium scale tests were carried out on 17 masonry walls subjected to out-of-plane bending. Several parameters were investigated, including the use of fire-resistant (cement-based) versus polymer-based insulating material, one sided versus two-sided insulation and/or TRM jacketing, placement of the TRM outside the insulation or in a sandwich form (over and under the insulation) and the displacement amplitude of the loading cycles. From the results obtained in this study the authors believe that TRM jacketing may be combined effectively with thermal insulation, which can be fire-resistant too.

Bond between textile-reinforced mortar (TRM) and concrete substrates: Experimental investigation

This paper presents an extended experimental study on the bond behaviour between textile-reinforced mortar (TRM) and concrete substrates. The parameters examined include: (a) the bond length (from 50 mm to 450 mm); (b) the number of TRM layers (from one to four); (c) the concrete surface preparation (grinding versus sandblasting); (d) the concrete compressive strength (15 MPa or 30 MPa); (e) the textile coating; and (f) the anchorage through wrapping with TRM jackets. For this purpose, a total of 80 specimens were fabricated and tested under double-lap direct shear. It is mainly concluded that: (a) after a certain bond length (between 200 mm and 300 mm for any number of layers) the bond strength marginally increases; (b) by increasing the number of layers the bond capacity increases in a non-proportional way, whereas the failure mode is altered; (c) concrete sandblasting is equivalent to grinding in terms of bond capacity and failure mode; (d) concrete compressive strength has a marginal effect on the bond capacity; (e) the use of coated textiles alters the failure mode and significantly increases the bond strength; and (f) anchorage of TRM through wrapping with TRM jackets substantially increases the ultimate load capacity.

Shear strengthening of full-scale RC T-beams using textile-reinforced mortar and textile-based anchors

This paper presents a study on the effectiveness of TRM jacketing in shear strengthening of full-scale reinforced concrete (RC) T-beams focussing on the behaviour of a novel end-anchorage system comprising textile-based anchors. The parameters examined in this study include: (a) the use of textile-based anchors as end-anchorage system of TRM U-jackets; (b) the number of TRM layers; (c) the textile properties (material, geometry); and (d) the strengthening system, namely textile-reinforced mortar (TRM) jacketing and fibre-reinforced polymer (FRP) jacketing for the case without anchors. In total, 11 full-scale RC T-beams were constructed and tested as simply supported in three-point bending. The results showed that: (a) The use of textile-based anchors increases dramatically the effectiveness of TRM U-jackets; (b) increasing the number of layers in non-anchored jackets results in an almost proportional increase of the shear capacity, whereas the failure mode is altered; (c) the use of different textile geometries with the same reinforcement ratio in non-anchored jackets result in practically equal capacity increase; (d) TRM jackets can be as effective as FRP jackets in increasing the shear capacity of full-scale RC T-beams. Finally, a simple design model is proposed to calculate the contribution of anchored TRM jackets to the shear capacity of RC T-beams.

Textile-reinforced mortar (TRM) versus fiber-reinforced polymers (FRP) in shear strengthening of concrete beams

This paper presents an experimental study on shear strengthening of rectangular reinforced concrete (RC) beams with advanced composite materials. Key parameters of this study include: (a) the strengthening system, namely textile-reinforced mortar (TRM) jacketing and fiber-reinforced polymer (FRP) jacketing, (b) the strengthening configuration, namely side-bonding, U-wrapping and full-wrapping, and (c) the number of the strengthening layers. In total, 14 RC beams were constructed and tested under bending loading. One of the beams did not receive any strengthening and served as control beam, eight received TRM jacketing, whereas the rest five received FRP jacketing. It is concluded that the TRM is generally less effective than FRP in increasing the shear capacity of concrete, however the effectiveness depends on both the strengthening configuration and the number of layers. U-wrapping strengthening configuration is much more effective than side-bonding in case of TRM jackets and the effectiveness of TRM jackets increases considerably with increasing the number of layers.