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Keywords = fiber-reinforced cementitious matrix (FRCM)

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18 pages, 4967 KiB  
Article
Effect of Pre-Damage on the Behavior of Axially and Eccentrically Compressed Concrete Cylinders Confined with PBO-FRCM
by Maciej Pazdan, Tomasz Trapko and Michał Musiał
Materials 2025, 18(12), 2881; https://doi.org/10.3390/ma18122881 - 18 Jun 2025
Viewed by 279
Abstract
In the case of strengthening building structures, the process usually involves elements that have a certain loading history and are typically subjected to loading during the strengthening process. In scientific research, on the other hand, strengthening is usually applied to elements that are [...] Read more.
In the case of strengthening building structures, the process usually involves elements that have a certain loading history and are typically subjected to loading during the strengthening process. In scientific research, on the other hand, strengthening is usually applied to elements that are not representative of real structures. This article presents a study of the effect of pre-damage on the behavior of eccentrically compressed concrete cylinders confined with PBO-FRCM (fabric-reinforced cementitious matrix with PBO fibers) composite. Concrete confinement introduces a favorable triaxial stress state, which leads to an increase in the compressive strength of concrete. FRCM systems are an alternative to FRP (fiber-reinforced polymer) composites. Replacing the polymer matrix with a mineral matrix primarily improves the fire resistance of the strengthening system. The elements were made of concrete with a compressive strength of about 40 MPa, which is typical for current reinforced concrete columns. Pre-damage was induced by loading the test elements to 80% of the average compressive strength and then fully unloading. The elements were then strengthened with three layers of PBO-FRCM composite and subjected to axial or eccentric compression with force applied at two different eccentricities. In addition to electric strain gauges, a digital image correlation system was used for measurements, to identify the initiation of PBO mesh overlap delamination. This study analyzed the elements in terms of load-bearing capacity, deformability, ductility, and failure mechanisms. In general, there was no negative effect of pre-damage on the behavior of the tested elements. Full article
(This article belongs to the Special Issue Strengthening, Repair, and Retrofit of Reinforced Concrete)
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26 pages, 6314 KiB  
Article
Influence of PBO-FRCM Composite Mesh Anchorage on the Strengthening Effectiveness of Reinforced Concrete Slabs
by Filip Grzymski, Tomasz Trapko and Michał Musiał
Materials 2025, 18(11), 2583; https://doi.org/10.3390/ma18112583 - 31 May 2025
Viewed by 516
Abstract
FRCM (Fabric-Reinforced Cementitious Matrix) composites, while providing an effective alternative to FRP (Fiber-Reinforced Polymer) strengthening systems when epoxy resins cannot be used, typically fail to achieve their full strengthening potential. Research indicates that appropriate mesh anchorage systems can minimize some of the undesirable [...] Read more.
FRCM (Fabric-Reinforced Cementitious Matrix) composites, while providing an effective alternative to FRP (Fiber-Reinforced Polymer) strengthening systems when epoxy resins cannot be used, typically fail to achieve their full strengthening potential. Research indicates that appropriate mesh anchorage systems can minimize some of the undesirable effects that limit FRCM composite performance. This study investigates the effectiveness of different anchorage systems for PBO (p-Phenylene Benzobis Oxazole) fibers in FRCM composites used for strengthening reinforced concrete slabs. A series of unidirectionally bent RC slabs were tested under four-point bending: an unstrengthened control element, slabs strengthened with PBO-FRCM without anchorage, with bar anchorage (GFRP bar in a groove), and with cord anchorage (PBO cord through the slab). The research focused on analyzing the load–deflection behavior and key strain mechanisms that influence structural performance. The findings indicate that a single layer of PBO-FRCM increases bending capacity, raises yield load, and delays initial cracking. Most significantly, the research reveals substantial differences in composite mesh utilization efficiency. This study confirms that mechanical anchorage, particularly bar anchorage, significantly enhances the effectiveness of PBO-FRCM strengthening systems by delaying composite detachment and allowing for greater utilization of the high-strength fiber material. These results contribute valuable insights for RC slabs using FRCM composite systems and the anchorage of their mesh. Full article
(This article belongs to the Special Issue Strengthening, Repair, and Retrofit of Reinforced Concrete)
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19 pages, 8021 KiB  
Article
Research on the Flexural Performance of Shield Tunnel Segments Strengthened with Fabric-Reinforced Cementitious Matrix Composite Panels
by Caixia Guo, Kaiwen Yang, Yichen Duan, Jiulin Li, Jianlin Wang and Weidong Lu
Buildings 2025, 15(8), 1355; https://doi.org/10.3390/buildings15081355 - 18 Apr 2025
Viewed by 385
Abstract
To investigate the strengthening effectiveness of Fabric-Reinforced Cementitious Matrix (FRCM) composites on shield tunnel segments, this study conducted four-point bending tests on FRCM composite panels. The influence of different cementitious matrices (engineered cementitious composite, ECC; ultra-high-performance concrete, UHPC) on the flexural behavior of [...] Read more.
To investigate the strengthening effectiveness of Fabric-Reinforced Cementitious Matrix (FRCM) composites on shield tunnel segments, this study conducted four-point bending tests on FRCM composite panels. The influence of different cementitious matrices (engineered cementitious composite, ECC; ultra-high-performance concrete, UHPC) on the flexural behavior of FRCM panels was systematically analyzed. Numerical simulations were additionally conducted to analyze deformation behavior, damage progression, and stress variations in steel reinforcements within standard structural segments strengthened with FRCM composite panels. A parametric analysis was performed to assess the effects of cementitious matrix type, panel thickness, and carbon fiber-reinforced polymer (CFRP) grid layers on the reinforcement efficiency. The experimental results demonstrated that FRCM composite panels exhibit superior flexural performance. Specimens with UHPC matrices exhibited higher cracking stresses and enhanced flexural stiffness during the elastic phase, while those with ECC matrices demonstrated advantages in post-peak hardening behavior and energy dissipation capacity. Both matrix types achieved similar cracking strains and comparable ultimate flexural strengths. Numerical simulations revealed that FRCM strengthening significantly improves the ultimate flexural bearing capacity of segments while effectively controlling deformation. For UHPC-based FRCM reinforced segments, the ultimate bearing capacity increased with both UHPC thickness and CFRP layer quantity. In contrast, ECC-based FRCM reinforced segments exhibited capacity enhancement primarily correlated with CFRP layer addition, with negligible sensitivity to ECC thickness variations. Full article
(This article belongs to the Special Issue Dynamic Response of Civil Engineering Structures under Seismic Loads)
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17 pages, 15945 KiB  
Article
Shear Strengthening with a Fiber-Reinforced Cementitious Matrix of Reinforced Concrete Elements Under Different Levels of Loads: An Experimental Investigation
by Pavlo Vegera, Viktor Borzovic, Zinovii Blikharskyi, Iryna Grynyova and Jaroslav Baran
Constr. Mater. 2024, 4(4), 721-737; https://doi.org/10.3390/constrmater4040039 - 22 Nov 2024
Viewed by 911
Abstract
This article explores the impact of strengthening reinforced concrete beams under different load levels, focusing on the use of polyphenylene benzobisoxazole (P.B.O.) fibers in a stabilized inorganic matrix to enhance the shear capacity. This research examines the interaction between modern composite materials and [...] Read more.
This article explores the impact of strengthening reinforced concrete beams under different load levels, focusing on the use of polyphenylene benzobisoxazole (P.B.O.) fibers in a stabilized inorganic matrix to enhance the shear capacity. This research examines the interaction between modern composite materials and existing reinforced concrete structures, highlighting the practical challenges when the full unloading of structures is impossible. The experiments demonstrate that strengthening significantly increases the shear strength, with a maximum enhancement of 25%. However, the effect decreases as the load applied during strengthening increases, dropping to 16% at 70% of the ultimate load. This research also highlights the importance of refining current calculation methods due to the complex stress–strain state of beams and the unpredictable nature of shear failures. It concludes that composite materials, especially fiber-reinforced cementitious matrix (FRCM) systems, provide a practical solution for enhancing structural performance while maintaining the integrity and safety of concrete elements. This article emphasizes that the strengthening efficiency should be adjusted based on the applied load, suggesting a 5% reduction in effectiveness for every 10% increase in the initial load level. The findings support the empirical hypothesis that the shear strength improvement diminishes linearly with higher load levels during strengthening. Full article
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12 pages, 3012 KiB  
Article
Simplified Procedure to Determine the Cohesive Material Law of Fiber-Reinforced Cementitious Matrix (FRCM)–Substrate Joints
by Francesco Focacci, Tommaso D’Antino and Christian Carloni
Materials 2024, 17(7), 1627; https://doi.org/10.3390/ma17071627 - 2 Apr 2024
Cited by 5 | Viewed by 1380
Abstract
Fiber-reinforced cementitious matrix (FRCM) composites have been largely used to strengthen existing concrete and masonry structures in the last decade. To design FRCM-strengthened members, the provisions of the Italian CNR-DT 215 (2018) or the American ACI 549.4R and 6R (2020) guidelines can be [...] Read more.
Fiber-reinforced cementitious matrix (FRCM) composites have been largely used to strengthen existing concrete and masonry structures in the last decade. To design FRCM-strengthened members, the provisions of the Italian CNR-DT 215 (2018) or the American ACI 549.4R and 6R (2020) guidelines can be adopted. According to the former, the FRCM effective strain, i.e., the composite strain associated with the loss of composite action, can be obtained by combining the results of direct shear tests on FRCM–substrate joints and of tensile tests on the bare reinforcing textile. According to the latter, the effective strain can be obtained by testing FRCM coupons in tension, using the so-called clevis-grip test set-up. However, the complex bond behavior of the FRCM cannot be fully captured by considering only the effective strain. Thus, a cohesive approach has been used to describe the stress transfer between the composite and the substrate and cohesive material laws (CMLs) with different shapes have been proposed. The determination of the CML associated with a specific FRCM–substrate joint is fundamental to capture the behavior of the FRCM-strengthened member and should be determined based on the results of experimental bond tests. In this paper, a procedure previously proposed by the authors to calibrate the CML from the load response obtained by direct shear tests of FRCM–substrate joints is applied to different FRCM composites. Namely, carbon, AR glass, and PBO FRCMs are considered. The results obtained prove that the procedure allows to estimate the CML and to associate the idealized load response of a specific type of FRCM to the corresponding CML. The estimated CML can be used to determine the onset of debonding in FRCM–substrate joints, the crack number and spacing in FRCM coupons, and the locations where debonding occurs in FRCM-strengthened members. Full article
(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)
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13 pages, 6299 KiB  
Article
Shear Performance of the Interface of Sandwich Specimens with Fabric-Reinforced Cementitious Matrix Vegetal Fabric Skins
by Lluís Gil, Luis Mercedes, Virginia Mendizabal and Ernest Bernat-Maso
Appl. Sci. 2024, 14(2), 883; https://doi.org/10.3390/app14020883 - 19 Jan 2024
Cited by 2 | Viewed by 1246
Abstract
The utilization of the vegetal fabric-reinforced cementitious matrix (FRCM) represents an innovative approach to composite materials, offering distinct sustainable advantages when compared to traditional steel-reinforced concrete and conventional FRCM composites employing synthetic fibers. This article introduces a design for sandwich solutions based on [...] Read more.
The utilization of the vegetal fabric-reinforced cementitious matrix (FRCM) represents an innovative approach to composite materials, offering distinct sustainable advantages when compared to traditional steel-reinforced concrete and conventional FRCM composites employing synthetic fibers. This article introduces a design for sandwich solutions based on a core of extruded polystyrene and composite skins combining mortar as a matrix and diverse vegetal fabrics as fabrics such as hemp and sisal. The structural behavior of the resulting sandwich panel is predominantly driven by the interaction between materials (mortar and polyurethane) and the influence of shear connectors penetrating the insulation layer. This study encompasses an experimental campaign involving double-shear tests, accompanied by heuristic bond-slip models for the potential design of sandwich solutions. The analysis extends to the examination of various connector types, including hemp, sisal, and steel, and their impact on the shear performance of the sandwich specimens. The results obtained emphasize the competitiveness of vegetal fabrics in achieving an effective composite strength comparable to other synthetic fabrics like glass fiber. Nevertheless, this study reveals that the stiffness of steel connectors outperforms vegetal connectors, contributing to an enhanced improvement in both stiffness and shear strength of the sandwich solutions. Full article
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22 pages, 4557 KiB  
Article
Prediction of Flexural Strength of RC Circular Columns Considering Lateral Confinement Effects of FRCM and Transverse Steel Reinforcement
by Min-Su Jo, Hyeong-Gook Kim, Dong-Hwan Kim, Jin-Hyeong Choi and Kil-Hee Kim
Buildings 2023, 13(9), 2361; https://doi.org/10.3390/buildings13092361 - 16 Sep 2023
Cited by 2 | Viewed by 1572
Abstract
There has recently been growing interest in making a sustainable and durable fiber reinforced cementitious matrix (FRCM) to improve the seismic performance of RC column members. However, most studies evaluating the lateral confinement effect on FRCM jacketing concrete have excluded the confinement effect [...] Read more.
There has recently been growing interest in making a sustainable and durable fiber reinforced cementitious matrix (FRCM) to improve the seismic performance of RC column members. However, most studies evaluating the lateral confinement effect on FRCM jacketing concrete have excluded the confinement effect of transverse steel reinforcement and focused solely on mechanical properties. This paper, based on existing studies, proposes a peak axial stress formula that considers the lateral confinement effects of FRCM composite and transverse steel reinforcement. Additionally, the study assesses the structural performance of FRCM composites with flexural strengthening in actual size RC circular columns and predicts the maximum flexural strength by applying the proposed formula. The proposed peak axial stress formula, considering the influence of transverse reinforcement, was compared with the experimental value (databases) and the predicted value, and the suitability was confirmed with a standard deviation of 27.6% and a coefficient of variation of 0.856. In addition, the maximum flexural strength of actual size RC circular columns predicted by applying this formula ranged from 0.97 to 1.02, which effectively predicted the experimental values. Full article
(This article belongs to the Section Building Structures)
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12 pages, 7691 KiB  
Article
Experimental Investigation of Concrete Cylinders Confined with PBO FRCM Exposed to Elevated Temperatures
by Reem Talo, Farid Abed, Ahmed El Refai and Yazan Alhoubi
Fire 2023, 6(8), 322; https://doi.org/10.3390/fire6080322 - 18 Aug 2023
Cited by 11 | Viewed by 2304
Abstract
Externally bonded fiber-reinforced polymers (FRPs) have been widely used for strengthening and retrofitting applications. However, their efficacy is hindered by the poor resistance of their epoxy resins to elevated temperatures and their limited compatibility with concrete substrates. To address these limitations, fabric-reinforced cementitious [...] Read more.
Externally bonded fiber-reinforced polymers (FRPs) have been widely used for strengthening and retrofitting applications. However, their efficacy is hindered by the poor resistance of their epoxy resins to elevated temperatures and their limited compatibility with concrete substrates. To address these limitations, fabric-reinforced cementitious matrix (FRCM), also known as textile reinforced mortar (TRM), systems have emerged as an alternative solution. In this study, experimental tests were performed on concrete cylinders confined with FRCM systems that consisted of mineral mortar and poliparafenilenbenzobisoxazole fabric (PBO). The cylinders with concrete strengths of 30, 45, and 70 MPa, were confined with one or two FRCM layers, and were subjected to different target temperatures (100, 400, and 800 °C). The experimental results highlighted the confinement effect of FRCMs on the compressive strength of the tested cylinders. Cylinders exposed to 100 °C exhibited a slight increase in their compressive strength, while no specific trend was observed in the compressive strength of cylinders heated to 400 °C. Specimens heated up to 800 °C experienced a significant reduction in strength, reaching up to 82%. Full article
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18 pages, 3947 KiB  
Article
Effects of Defects on Masonry Confinement with Inorganic Matrix Composites
by Gian Piero Lignola, Gaetano Manfredi and Andrea Prota
Materials 2023, 16(13), 4737; https://doi.org/10.3390/ma16134737 - 30 Jun 2023
Cited by 1 | Viewed by 1093
Abstract
Fabric-reinforced cementitious matrix (FRCM) composites are currently considered a suitable solution for strengthening existing structures. Confinement applications are still being investigated, since experimental programs showed significant scatter in the results and theoretical models are struggling to become established as a consequence. The main [...] Read more.
Fabric-reinforced cementitious matrix (FRCM) composites are currently considered a suitable solution for strengthening existing structures. Confinement applications are still being investigated, since experimental programs showed significant scatter in the results and theoretical models are struggling to become established as a consequence. The main aim of this study is the identification of potential sources of scatter in the confinement efficiency of FRCM wrappings, in defects such as fiber slip within the matrix or imperfect straightening of fibers, or premature failure of fibers once exposed after complete matrix cracking. A theoretical incremental approach is proposed to simulate such effects. The approach is incremental, but not iterative, so that no convergence is required and the incremental step size has an impact only on the smoothness of the nonlinear theoretical stress vs. strain curves of the FRCM confined material, among other simulation results. Theoretical results are compared to experimental outcomes of previous tests. The main source of variability can be identified in the cited defects, and the approach can be considered satisfactory to simulate the effects of defects and the high scatter found in experimental results; however, further uncertainties in the behavior of materials can be included in future refinements of this study. Full article
(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)
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19 pages, 8671 KiB  
Article
Shear Strengthening of RC Beams Using Fabric-Reinforced Cementitious Matrix, Carbon Plates, and 3D-Printed Strips
by Yasmin Zuhair Murad, Hanady Al-Mahmood, Ahmad Tarawneh, Ahmad J. Aljaafreh, Ayoub AlMashaqbeh, Raghad Abdel Hadi and Rund Shabbar
Sustainability 2023, 15(5), 4293; https://doi.org/10.3390/su15054293 - 28 Feb 2023
Cited by 3 | Viewed by 2326
Abstract
Existing reinforced concrete (RC) structures suffer from degradation in their structural capacity. These structures require strengthening and retrofitting to integrate sustainability and improve their serviceability and durability. RC members strengthened with fiber-reinforced polymer (FRP) composites usually suffer from FRP debonding; therefore, researchers proposed [...] Read more.
Existing reinforced concrete (RC) structures suffer from degradation in their structural capacity. These structures require strengthening and retrofitting to integrate sustainability and improve their serviceability and durability. RC members strengthened with fiber-reinforced polymer (FRP) composites usually suffer from FRP debonding; therefore, researchers proposed several types of sustainable materials to overcome the shortcomings of FRP composites. Limited experimental studies have been conducted for shear strengthening of RC beams using sustainable fabric-reinforced cementitious matrix (FRCM) composites; moreover, the application of 3D-printed strips in strengthening RC beams has never been established. The current research experimentally investigates the efficiency of FRCM composites, 3D-printed sheets (CD), and CFRP plates (CP) in strengthening RC beams that are weak in shear. Various strengthening configurations were adopted, including vertical, oblique, zigzag, and several-slanted layouts. Eight simply supported beams were prepared to find the most efficient shear-strengthening configuration and material for RC beams. Test results showed that FRCM and CP are both efficient for shear strengthening in terms of maximum load capacity, initial stiffness, and ductility. However, CD showed a limited effect on enhancing the performance of shear-strengthened beams. The best shear enhancement was found in the beam strengthened with vertical CP, with improvements in load-carrying capacity, stiffness, and ductility of 43%, 23%, and 23%, respectively. The vertical and oblique strengthening configurations were more efficient than the zigzag and several-slanted layouts. The ACI 440.2R-17 model yielded accurate predictions with an average (Vc, test/Vc, ACI 440) of 1.11. Full article
(This article belongs to the Section Sustainable Materials)
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12 pages, 3234 KiB  
Article
Static Analysis of Wooden Beams Strengthened with FRCM-PBO Composite in Bending
by Piotr Kazimierz Sokołowski and Paweł Grzegorz Kossakowski
Materials 2023, 16(5), 1870; https://doi.org/10.3390/ma16051870 - 24 Feb 2023
Cited by 8 | Viewed by 1894
Abstract
The article presents an analysis of the static work of bent solid-wood beams reinforced with FRCM–PBO (fiber-reinforced cementitious matrix–p-phenylene benzobis oxazole) composite. In order to ensure better adhesion of the FRCM–PBO composite to the wooden beam, a layer of mineral resin and quartz [...] Read more.
The article presents an analysis of the static work of bent solid-wood beams reinforced with FRCM–PBO (fiber-reinforced cementitious matrix–p-phenylene benzobis oxazole) composite. In order to ensure better adhesion of the FRCM–PBO composite to the wooden beam, a layer of mineral resin and quartz sand was applied between the composite and the wooden beam. Ten wooden pine beams with dimensions of 80 × 80 × 1600 mm were used for the tests. Five wooden beams, unreinforced, were used as referenced elements and another five were reinforced with FRCM–PBO composite. The tested samples were subjected to a four-point bending test in which the static scheme of a simply supported beam subjected to two symmetrical concentrated forces was used. The main purpose of the experiment was to estimate the load capacity, the flexural modulus and the maximum bending stress. The time needed to destroy the element and the deflection were also measured. The tests were carried out based on the PN-EN 408: 2010 + A1 standard. The material used for the study was also characterized. The methodology and assumptions adopted in the study were presented. The tests confirmed a significant increase in destructive force by 141.46%, maximum bending stress by 118.9%, modulus of elasticity by 18.32%, time needed to destroy the sample by 106.56% and deflection by 115.58% compared to the reference beams. The unusual method of wood reinforcement presented in the article can be considered as innovative, characterized not only by a significant load capacity margin exceeding 141%, but also by simplicity of application. Full article
(This article belongs to the Special Issue New Advances in Strengthening of Structural Timber)
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13 pages, 5524 KiB  
Article
Experimental Test of Reinforced Timber of FRCM-PBO with Pull-Off Adhesion Method
by Piotr Sokołowski, Paulina Bąk-Patyna, Dominika Bysiec and Tomasz Maleska
Materials 2022, 15(21), 7702; https://doi.org/10.3390/ma15217702 - 2 Nov 2022
Cited by 2 | Viewed by 1729
Abstract
The article describes the results of pull-off adhesion strength of the FRCM-PBO (Fiber Reinforced Cementitious Matrix-p-Phenylene benzobis oxazole) composite adhered to the epoxy resin layer which is the connector with the timber beam. In addition, this paper shows the results of the tests [...] Read more.
The article describes the results of pull-off adhesion strength of the FRCM-PBO (Fiber Reinforced Cementitious Matrix-p-Phenylene benzobis oxazole) composite adhered to the epoxy resin layer which is the connector with the timber beam. In addition, this paper shows the results of the tests of resistance to pull-off the epoxy resin layer from the pine beam. The tests were carried out based on the Polish Standard PN-EN 1542. The Pearson linear correlation analysis was also carried out in order to determine the correlation between the obtained results and the destructive forces. The factors that occurred during the test that may affect its results, such as the method of applying the bursting force, surface preparation of the tested elements and the types of substrate destruction, were also characterized. The experimental data show that in all the tested samples, non-initial adhesive destruction between the adhesive layer and the disc was observed. Full article
(This article belongs to the Special Issue Rheology and Mechanical Properties of Wood and Wood-Based Materials)
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19 pages, 7216 KiB  
Article
Clevis-Grip Tensile Tests on Basalt, Carbon and Steel FRCM Systems Realized with Customized Cement-Based Matrices
by Dario De Domenico, Natale Maugeri, Paolo Longo, Giuseppe Ricciardi, Giuseppe Gullì and Luigi Calabrese
J. Compos. Sci. 2022, 6(9), 275; https://doi.org/10.3390/jcs6090275 - 17 Sep 2022
Cited by 10 | Viewed by 2657
Abstract
The tensile properties of fabric-reinforced cementitious matrix (FRCM) composites are experimentally investigated through clevis-grip tensile tests (according to AC434 provisions) on FRCM coupons realized with customized (ad hoc developed in this paper) cement-based matrices. The tested FRCM coupons are reinforced with basalt, carbon, [...] Read more.
The tensile properties of fabric-reinforced cementitious matrix (FRCM) composites are experimentally investigated through clevis-grip tensile tests (according to AC434 provisions) on FRCM coupons realized with customized (ad hoc developed in this paper) cement-based matrices. The tested FRCM coupons are reinforced with basalt, carbon, or steel fabrics, and are prepared with three different matrices: one-component mortar incorporating dispersible copolymer powders of vinyl acetate and ethylene (matrices A and B) and two-component mortar with carboxylated styrene–butadiene copolymer liquid resin (matrix C). This has made it possible to investigate the mechanical compatibility between different mortar matrices and fabrics and the resulting tensile properties of FRCM composites in the uncracked, cracking, and fully cracked phases. Experimental results are critically analyzed in terms of stress–strain curves and failure mechanisms comparatively for the analyzed FRCM systems. It has been shown that the matrix B exhibits a good compatibility with the basalt pre-impregnated fabric, while the matrix C appears to be the most suitable candidate to optimize the interfacial stress transfer at the fiber–matrix interface for all fabrics, thus exalting the mechanical performances in terms of tensile strength and ultimate strain. The results of this experimental program can be useful for designing optimized mortar mixes aimed at realizing novel FRCM composites or at improving existing FRCM systems by suitably accounting for compatibility behavior and slippage at the fabric–matrix interface. Full article
(This article belongs to the Section Fiber Composites)
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16 pages, 10110 KiB  
Article
Natural FRCM and Heritage Buildings: Experimental Approach to Innovative Interventions on “Wall Beams”
by Riccardo Liberotti, Federico Cluni, Francesco Faralli and Vittorio Gusella
Buildings 2022, 12(8), 1076; https://doi.org/10.3390/buildings12081076 - 23 Jul 2022
Cited by 10 | Viewed by 2268
Abstract
In this paper, an innovative strengthening system for masonry walls made of externally bonded Fabric-Reinforced Cementitious Matrix (FRCM) is presented. Due to the good mechanical properties and the compatibility with the architectural heritage, the FRCM is an adequate alternative to the use of [...] Read more.
In this paper, an innovative strengthening system for masonry walls made of externally bonded Fabric-Reinforced Cementitious Matrix (FRCM) is presented. Due to the good mechanical properties and the compatibility with the architectural heritage, the FRCM is an adequate alternative to the use of Fiber-Reinforced Polymer (FRP) composites and other traditional techniques. The proposed system is applied to the strengthening of a classical architectural typology in cultural heritage architecture, which is the “in falso” masonry: a load-bearing wall built over a masonry vault, and hence without a direct load path to the ground. A research program, characterized by an experimental campaign, has been started in order to devise and verify an optimal strengthening system that assures for the masonry wall a structural behavior similar to a “wall beam”, so to prevent progressive collapses when the underlying masonry vault loses its carrier function. In particular, rather than the canonical application, consisting in widespread application to the whole surface of the masonry wall, an innovative intervention made of “Green Tape” of composites has been designed and verified by a specifically designed experimental set-up. The main objective of the research is to propose a reinforcement strategy not detrimental to unmovable artistic assets and tied to the safety and robustness of the architectural heritage. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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15 pages, 4866 KiB  
Article
Fabric-Reinforced Cementitious Matrix (FRCM) Carbon Yarns with Different Surface Treatments Embedded in a Cementitious Mortar: Mechanical and Durability Studies
by Francesca Bompadre and Jacopo Donnini
Materials 2022, 15(11), 3927; https://doi.org/10.3390/ma15113927 - 31 May 2022
Cited by 8 | Viewed by 2346
Abstract
Nowadays, FRCM systems are increasingly used for the strengthening and retrofitting of existing masonry and reinforced concrete structures. Their effectiveness strongly depends on the bond that develops at the interface between multifilament yarns, which constitute the reinforcing fabric, and the inorganic matrix. It [...] Read more.
Nowadays, FRCM systems are increasingly used for the strengthening and retrofitting of existing masonry and reinforced concrete structures. Their effectiveness strongly depends on the bond that develops at the interface between multifilament yarns, which constitute the reinforcing fabric, and the inorganic matrix. It is well known that fabric yarns, especially when constituted by dry carbon fibers, have poor chemical-physical compatibility with inorganic matrices. For this reason, many efforts are being concentrated on trying to improve the interface compatibility by using different surface treatments on multifilament yarns. In this paper, three different surface treatments have been considered. The first two involve yarn pre-impregnation with flexible epoxy resin or nano-silica coating, while the third one involves a fiber oxidation process. Uniaxial tensile tests were carried out on single carbon yarns to evaluate tensile strength, elastic modulus and ultimate strain before and after surface treatments, and also after yarn exposure to accelerated artificial aging conditions (1000 h in saline or alkaline solutions at 40 °C), to evaluate their long-term behavior in aggressive environments. Pull-out tests on single carbon yarns embedded in a cementitious mortar were also carried out, under normal environmental conditions and after artificial exposure. Epoxy proved to be the most effective treatment, by increasing the yarn tensile strength of 34% and the pull-out load of 138%, followed by nano-silica (+9%; +40%). All surface treatments were shown to remain effective even after artificial environmental exposures, with a maximum reduction of yarn tensile strength of about 13%. Full article
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