Fiber-Reinforced Polymers and Fiber-Reinforced Cement-Based Mortars in Repair/Strengthening Methods of Masonry and Reinforced Concrete Structural Members

A special issue of Fibers (ISSN 2079-6439).

Deadline for manuscript submissions: closed (30 September 2023) | Viewed by 11279

Special Issue Editors


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Guest Editor
Division of Structural Engineering Science, Democritus University of Thrace, Xanthi, Greece
Interests: FRP; reinforced concrete; shear; tentioned concrete; steel fiber reinforced concrete; repair; tortion; structural health monitoring; strengthening and structural rehabilitation
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Guest Editor
Reinforced Concrete Lab., Department of Civil Engineering, Structural Engineering Division, Democritus University of Thrace, University Campus, Kimmeria, 67100 Xanthi, Greece
Interests: reinforced concrete structures; seismic design of reinforced structures; damage detection of structures based on piezoelectric sensors; seismic pathology of reinforced concrete structures; rehabilitation (repair-strengthening) of structures; pre-stressed concrete
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A significant number of existing masonry and reinforced concrete (RC) buildings were designed and constructed according to older Codes with inadequate seismic requirements regarding the provisions of modern Code Standards. Many of these structures have also low-quality building materials, insufficient load bearing or seismic capacity, inadequate reinforcement, several morphological problems and damages due to corrosion, cracking, ageing and inevitable deterioration during their service life. Apparently, the structural members of such buildings present weaknesses concerning their strength, ductility, stiffness and deformability. Upgrading in this type of structure is essential in order to avoid excessive decays, sudden total or local collapses or even loss of life. However, proper strengthening works is a complex, highly labor-intensive, time-consuming and usually expensive process that is difficult to widely apply in the majority of the existing vulnerable structures.

Innovative materials manufactured of glass, carbon, aramid or basalt continuous fibers in polymer matrix (Fiber-Reinforced Polymers or FRPs) have been proposed as alternatives for the substitution of the traditional steel reinforcement. Furthermore, the addition of discontinuous fibers in concrete has long been recognized as a non-conventional mass reinforcement that enhances the mechanical properties of cement-based mortars and concretes. Fiber-reinforced concrete with short randomly distributed fibers exhibits significant resistance to the formation and growth of cracks, increased post-cracking ductility and energy dissipation capacity. Furthermore, FRPs and non-metallic Fiber-Reinforced Cement-based Mortars are both recommended in cases that the possibility of corrosion in existing structures may cause serious safety and financial concerns in harsh environments. The lightweight, non-corrosive and non-magnetic nature of these composite materials are some of their attractive characteristics that make them a promising upgrading technique in repair/strengthening works of existing deficient masonry and RC structures.

This Special Issue brings together experimental and analytical studies aiming to provide a further contribution in advancing knowledge and a comprehensive overview on the advancements of FRPs and Fiber-Reinforced Cement Mortars and their utilization as internal or externally applied in novel repair/strengthening techniques of masonry and RC structural members. Research is encouraged in, but not limited to, the following aspects: Repair and strengthening methods, mechanical properties, bond behavior, structural shapes of the fiber composites to enhance strength, stiffness ductility and poor deformability of deficient or damaged masonry and RC structures by experimental investigations or/and numerical simulation under various loading conditions. Original research papers, case studies, communications and authoritative review articles are invited for this Special Issue.

Papers selected for this Special Issue will be subject to a rigorous peer-review procedure with the aim of rapid and wide dissemination of the research results, developments and applications.

Prof. Dr. Constantin Chalioris
Prof. Dr. Chris Karayannis
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fibers is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • fiber-reinforced polymers (FRPs)
  • fiber-reinforced cement-based mortars
  • concrete
  • reinforced concrete (RC)
  • masonry
  • repair
  • strengthening
  • mechanical properties
  • experimental study
  • bond behavior
  • numerical modeling
  • structural behavior
  • field applications
  • case studies
  • structural health monitoring (SHM) of fiber-reinforced structural members

Published Papers (6 papers)

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Research

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30 pages, 14678 KiB  
Article
Repairing of One-Way Solid Slab Exposed to Thermal Shock Using CFRP: Experimental and Analytical Study
by Mousa Shhabat, Ahmed Ashteyat and Mu’tasim Abdel-Jaber
Fibers 2024, 12(2), 18; https://doi.org/10.3390/fib12020018 - 19 Feb 2024
Viewed by 980
Abstract
This research was conducted to investigate, experimentally, theoretically, and numerically, the use of CFRP materials for repairing a reinforced concrete one-way solid slab exposed to thermal shock. Nine slabs, measuring 1800 mm in length, 500 mm in width, and 100 mm in depth, [...] Read more.
This research was conducted to investigate, experimentally, theoretically, and numerically, the use of CFRP materials for repairing a reinforced concrete one-way solid slab exposed to thermal shock. Nine slabs, measuring 1800 mm in length, 500 mm in width, and 100 mm in depth, were cast. Seven of these slabs underwent thermal shock at a temperature of 600 °C, rapidly cooled by immersion in water for 15 min. Three primary parameters were examined: the type of CFRP (rope, strip, and sheet), spacing (100 and 200 mm), and the number of sheet layers (one and two). The experimental results revealed a significant decrease of approximately 45.4% in the compressive strength of the concrete after exposure to thermal shock. The thermally shocked RC slab showed a reduction in ultimate capacity by 15.4% and 38.5% in stiffness compared to the control slab. The results underscored the efficacy of CFRP materials, with all repair configurations exhibiting a substantial increase in maximum load capacity and stiffness. Capacity enhancement ranged from 23.7% to 53.4%, while stiffness improvement ranged from 27.6% to 57.1%. Notably, all repair configurations effectively minimized the maximum deflection. This reduction in deflection ranged from 5.2% to 26% compared to the control slab. Numerical results demonstrated strong concurrence with experimental results for both capacity and deflection. The enhancement in capacity ranged from 0.7% to 10.4%, while deflection decreased within a range from 0.95% to 14.16% compared to experimental results. Full article
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19 pages, 3438 KiB  
Article
Failure Mode Prediction of Unreinforced Masonry (URM) Walls Retrofitted with Cementitious Textile Reinforced Mortar (TRM)
by Athanasia K. Thomoglou, Martha A. Karabini, Dimitra V. Achillopoulou, Theodoros C. Rousakis and Constantin E. Chalioris
Fibers 2023, 11(6), 53; https://doi.org/10.3390/fib11060053 - 15 Jun 2023
Cited by 5 | Viewed by 1577
Abstract
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 [...] Read more.
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. Full article
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25 pages, 10545 KiB  
Article
An Electromechanical Impedance-Based Application of Realtime Monitoring for the Load-Induced Flexural Stress and Damage in Fiber-Reinforced Concrete
by Maria C. Naoum, George M. Sapidis, Nikos A. Papadopoulos and Maristella E. Voutetaki
Fibers 2023, 11(4), 34; https://doi.org/10.3390/fib11040034 - 11 Apr 2023
Cited by 5 | Viewed by 1518
Abstract
Effective real-time structural health monitoring in concrete structures is paramount to evaluating safety conditions and the timely maintenance of concrete structures. Especially, the presence of discrete fibers in fiber-reinforced concrete restrains crack propagation into small and thin cracks, which increases the difficulty in [...] Read more.
Effective real-time structural health monitoring in concrete structures is paramount to evaluating safety conditions and the timely maintenance of concrete structures. Especially, the presence of discrete fibers in fiber-reinforced concrete restrains crack propagation into small and thin cracks, which increases the difficulty in detecting damage. In this study, an array of piezoelectric lead zirconate titanate (PZT) transducers was applied to study the effects of external load-induced flexural stress and damage in fiber-reinforced concrete beams using the electromechanical impedance (EMI) or electromechanical admittance (EMA) methods. Beams were subjected to a four-point bending test under repeatable loading, while PZTs evaluated corresponding flexural stress and induced damage simultaneously. Due to the influence of the medium’s stress fields in the different types of wave propagation in structural elements, PZT transducers measurements are accordingly affected under variable stress fields, in addition to the effect of the higher level of damage that occurred in the medium. According to the results of the tests, variation in EMA signatures, following flexural stress and gradual damage changes, provided convincing evidence for predicting stress and damage development. Full article
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14 pages, 2645 KiB  
Article
Improving the Performance of Lightweight Crumb Rubber Mortar Using Synthetic, Natural, and Hybrid Fiber Reinforcements
by S. M. Iqbal S. Zainal, Debbie Mattius, Zulhelmi Baba, Ahmad Nurfaidhi Rizalman and Farzad Hejazi
Fibers 2023, 11(1), 9; https://doi.org/10.3390/fib11010009 - 12 Jan 2023
Cited by 5 | Viewed by 2025
Abstract
The global market for tires is ever-growing, and partially replacing sand with crumb rubber (CR) as fine aggregates in concrete could reduce environmental pollution. However, the main barrier to the complete usage of recycled tire crumbs in construction is the deterioration effect of [...] Read more.
The global market for tires is ever-growing, and partially replacing sand with crumb rubber (CR) as fine aggregates in concrete could reduce environmental pollution. However, the main barrier to the complete usage of recycled tire crumbs in construction is the deterioration effect of CR on the mechanical properties of cement-based composites. Therefore, this paper attempts to improve the fresh and hardened properties of crumb rubber mortar (CRM) by incorporating polypropylene-polyethylene synthetic fibers with coconut and kenaf natural fibers as reinforcements. A total of 18 mix designs were developed with varying fiber combinations and rubber crumb replacement. Subsequently, parametric studies with chemical admixture were conducted at 3, 7, and 28 days to improve the flowability and resulting mechanical properties of the fiber-reinforced CRM. According to the results, the single and hybrid fibers positively improved the mechanical properties of cement mortar at 5–15% CR replacement. It can be concluded that adding single and hybrid fibers enhanced the performance of cement mortar modified with tire crumb rubber aggregates by providing varying degrees of improvement. Full article
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22 pages, 9453 KiB  
Article
Influence of Different Surfactants on Carbon Fiber Dispersion and the Mechanical Performance of Smart Piezoresistive Cementitious Composites
by Athanasia K. Thomoglou, Maria G. Falara, Fani I. Gkountakou, Anaxagoras Elenas and Constantin E. Chalioris
Fibers 2022, 10(6), 49; https://doi.org/10.3390/fib10060049 - 31 May 2022
Cited by 18 | Viewed by 2815
Abstract
This experimental study presents the effect of different surfactants on micro-scale carbon fiber (CFs) distribution into carbon fiber reinforced cement-based composites (CFRC) in terms of flexural and compressive strength, stiffness, flexural toughness, and strain-sensing ability. Conducting a narrative review of the literature focusing [...] Read more.
This experimental study presents the effect of different surfactants on micro-scale carbon fiber (CFs) distribution into carbon fiber reinforced cement-based composites (CFRC) in terms of flexural and compressive strength, stiffness, flexural toughness, and strain-sensing ability. Conducting a narrative review of the literature focusing on the fibers’ separation, this paper follows a methodology introducing a combination of mechanical and chemical carbon fibers dispersion, as well as the different mixing processes (wet or dry). Three types of surfactants: Carboxymethyl cellulose (CMC), cellulose nanocrystal (CNC), and superplasticizer (SP), were applied to evaluate the CFs distribution in the cement paste matrix. Compressive and flexural strength, modulus of elasticity, and ductility of the cement-based composites (CFRC) reinforced with 0.5 wt.% CFs were investigated by three-point bending and compressive tests; flexure tests were also conducted on notched 20 × 20 × 80 mm specimens using the Linear Elastic Fracture Mechanics (L.E.F.M.) theory. Moreover, the electrical conductivity and the piezoresistive response were determined by conducting electrical resistance measurements and applying compressive loading simultaneously. The results clearly reveal that the CFs/SP solution or the CFs’ dry incorporation led to a significant enhancement of flexural strength by 32% and 23.7%, modulus of elasticity by 30% and 20%, and stress-sensing ability by 20.2% and 18.2%, respectively. Although the wet mixing method exhibits improved mechanical and electrical conductivity performance, constituting an adequate strain and crack sensor, the authors propose dry mixing as the most economical method, in addition to the enhanced mechanical and electrical responses. The authors recommend an effective method for structural health monitoring systems combining an economical CFs insertion in cementitious smart sensors with great mechanical and self-sensing responses. Full article
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Review

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17 pages, 6427 KiB  
Review
Review of Out-of-Plane Strengthening Techniques of Unreinforced Masonry Walls
by Athanasia K. Thomoglou, P. Jagadesh and Maristella E. Voutetaki
Fibers 2023, 11(9), 78; https://doi.org/10.3390/fib11090078 - 19 Sep 2023
Cited by 2 | Viewed by 1360
Abstract
When a seismic load is applied horizontally or laterally on unreinforced masonry walls (URM), the walls behave in two different ways, viz., in-plane (IP) and out-of-plane (OoP). This review beneficially provides a literature overview of the most cited research papers on Scopus, and [...] Read more.
When a seismic load is applied horizontally or laterally on unreinforced masonry walls (URM), the walls behave in two different ways, viz., in-plane (IP) and out-of-plane (OoP). This review beneficially provides a literature overview of the most cited research papers on Scopus, and the database is evaluated with VOSviewer software for scientometric analysis. This review paper delves into the practical applications of various types of reinforcement for masonry walls, specifically focusing on four commonly used systems: externally bonded strengthening techniques using fiber-reinforced polymers (FRP), steel-reinforced grout (SRG), fabric-reinforced cementitious mortar (FRCM), and textile-reinforced mortars (TRM). The main objective of the paper is to explore the efficacy of these reinforcement techniques in strengthening masonry walls, and to provide a comprehensive overview of their respective advantages and limitations. A further detailed study of the extent of the literature is performed about the effect of the different strengthening systems on the mechanical properties of different categories of masonry walls like a cement block, stone, and clay brick are described and categorized. The efficiency of OoP strengthening can depend on various factors, such as the types of masonry units, the rendering mortar, the type of strengthening system, the bond between the different materials interfaces, the geometry of the wall, and the loading conditions. By utilizing the practical method of Dematel (Decision-making trial and evaluation laboratory) analysis, this review can delve deeply into the impact of various factors and precisely identify the crucial components of the cause-and-effect connection. The results indicate that the bond between material interfaces is the critical factor. This meticulous and structured review offers valuable perspectives for researchers and engineers, showcasing current research trends and presenting potential avenues for future exploration. Full article
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