Fiber-Reinforced Polymers and Fiber-Reinforced Cement Composites as Concrete Reinforcement

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

Deadline for manuscript submissions: closed (30 April 2021) | Viewed by 32913

Special Issue Editor

Special Issue Information

Dear Colleagues,

Reinforced concrete (RC) structural members have originally been designed using steel reinforcing bars and stirrups. In recent decades, innovative materials manufactured out 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 traditional steel reinforcement or for retrofitting applications in RC structures.

Further, the addition of discontinuous fibers in concrete has long been recognized as a non-conventional mass reinforcement that enhances the mechanical properties of concrete. 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.

FRPs and non-metallic fiber-reinforced cement-based composites are both recommended in cases where the possibility of corrosion in steel RC 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 the attractive characteristics that make them a promising reinforcement technique in new RC construction and rehabilitation/strengthening works of existing deficient RC structures.

This Special Issue brings together experimental and analytical studies aiming to further knowledge and provide a comprehensive overview of the latest advancements in FRPs and fiber-reinforced cement composites and their utilization as internal or externally applied reinforcing material. We are especially interested in studies addressing the following aspects (amongst others): mechanical properties, cracking performance, bond behavior, tension stiffening, rehabilitation, repair and strengthening techniques, structural shapes of the fiber composites such as bars, rods, ropes, sheets, laminates, short fibers, and numerical simulation under various loading conditions. Original research papers, case studies, communications, and authoritative review articles are all 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 research results, developments, and applications.

Dr. Constantin Chalioris
Guest Editor

Manuscript Submission Information

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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

  • concrete
  • reinforced concrete (RC)
  • fiber-reinforced polymers (FRPs)
  • fiber-reinforced cement-based composites
  • geogrid reinforcement
  • tension stiffening
  • mechanical properties
  • bond behavior
  • numerical modeling
  • structural behavior
  • field applications
  • case studies
  • repair/strengthening

Published Papers (7 papers)

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Research

23 pages, 9034 KiB  
Article
Cracking Diagnosis in Fiber-Reinforced Concrete with Synthetic Fibers Using Piezoelectric Transducers
Fibers 2022, 10(1), 5; https://doi.org/10.3390/fib10010005 - 09 Jan 2022
Cited by 50 | Viewed by 3664
Abstract
The addition of short fibers in concrete mass offers a composite material with advanced properties, and fiber-reinforced concrete (FRC) is a promising alternative in civil engineering applications. Recently, structural health monitoring (SHM) and damage diagnosis of FRC has received increasing attention. In this [...] Read more.
The addition of short fibers in concrete mass offers a composite material with advanced properties, and fiber-reinforced concrete (FRC) is a promising alternative in civil engineering applications. Recently, structural health monitoring (SHM) and damage diagnosis of FRC has received increasing attention. In this work, the effectiveness of a wireless SHM system to detect damage due to cracking is addressed in FRC with synthetic fibers under compressive repeated load. In FRC structural members, cracking propagates in small and thin cracks due to the presence of the dispersed fibers and, therefore, the challenge of damage detection is increasing. An experimental investigation on standard 150 mm cubes made of FRC is applied at specific and loading levels where the cracks probably developed in the inner part of the specimens, whereas no visible cracks appeared on their surface. A network of small PZT patches, mounted to the surface of the FRC specimen, provides dual-sensing function. The remotely controlled monitoring system vibrates the PZT patches, acting as actuators by an amplified harmonic excitation voltage. Simultaneously, it monitors the signal of the same PZTs acting as sensors and, after processing the voltage frequency response of the PZTs, it transmits them wirelessly and in real time. FRC cracking due to repeated loading ad various compressive stress levels induces change in the mechanical impedance, causing a corresponding change on the signal of each PZT. The influence of the added synthetic fibers on the compressive behavior and the damage-detection procedure is examined and discussed. In addition, the effectiveness of the proposed damage-diagnosis approach for the prognosis of final cracking performance and failure is investigated. The objectives of the study also include the development of a reliable quantitative assessment of damage using the statistical index values at various points of PZT measurements. Full article
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26 pages, 12297 KiB  
Article
Seismic Performance of RC Beam–Column Joints Designed According to Older and Modern Codes: An Attempt to Reduce Conventional Reinforcement Using Steel Fiber Reinforced Concrete
Fibers 2021, 9(7), 45; https://doi.org/10.3390/fib9070045 - 05 Jul 2021
Cited by 8 | Viewed by 5815
Abstract
An analytical and experimental investigation was conducted herein to examine the cyclic load behavior of beam–column joint subassemblages, typical of both the modern reinforced concrete (RC) structures and of the pre-1960s–1970s existing ones. Seven exterior RC beam–column joint subassemblages were constructed and subjected [...] Read more.
An analytical and experimental investigation was conducted herein to examine the cyclic load behavior of beam–column joint subassemblages, typical of both the modern reinforced concrete (RC) structures and of the pre-1960s–1970s existing ones. Seven exterior RC beam–column joint subassemblages were constructed and subjected to earthquake-type loading. Three specimens were designed according to the requirements of the Eurocode (EC) for ductility class medium (DCM), while the other three specimens possessed poor seismic details, conforming to past building codes. The hysteresis behavior of the subassemblages was evaluated. An analytical model was used to calculate the ultimate shear capacity of the beam–column joint area, while also predicting accurately the failure mode of the specimens. It was clearly demonstrated experimentally and analytically that it is possible for excessive seismic damage of the beam–column joint region to occur when designing according to the current European building codes. In addition, the proposed analytical model was found to be very satisfactory in accurately predicting seismic behavior and in preventing the premature brittle shear failure of the joints. The seventh subassemblage, constructed with steel fiber RC and significantly less transverse reinforcement than that required according to the EC, exhibited satisfactory ductile seismic performance, demonstrating the effectiveness of the proposed design solution. Full article
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15 pages, 5341 KiB  
Article
Application of X-Shaped CFRP Ropes for Structural Upgrading of Reinforced Concrete Beam–Column Joints under Cyclic Loading–Experimental Study
Fibers 2021, 9(7), 42; https://doi.org/10.3390/fib9070042 - 01 Jul 2021
Cited by 34 | Viewed by 5055
Abstract
The effectiveness of externally applied fiber-reinforced polymer (FRP) ropes made of carbon fibers in X-shape formation and in both sides of the joint area of reinforced concrete (RC) beam–column connections is experimentally investigated. Six full-scale exterior RC beam–column joint specimens are tested under [...] Read more.
The effectiveness of externally applied fiber-reinforced polymer (FRP) ropes made of carbon fibers in X-shape formation and in both sides of the joint area of reinforced concrete (RC) beam–column connections is experimentally investigated. Six full-scale exterior RC beam–column joint specimens are tested under reverse cyclic deformation. Three of them have been strengthened using carbon FRP (CFRP) ropes that have been placed diagonally in the joint as additional, near surface-mounted reinforcements against shear. Full hysteretic curves, maximum applied load capacity, damage modes, stiffness and energy dissipation values per each loading step are presented and compared. Test results indicated that joint sub assemblages with X-shaped CFRP ropes exhibited improved hysteretic behavior and ameliorated performance with respect to the reference specimens. The effectiveness and the easy-to-apply character of the presented strengthening technique is also discussed. Full article
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17 pages, 8513 KiB  
Article
Development of a Robot-Based Multi-Directional Dynamic Fiber Winding Process for Additive Manufacturing Using Shotcrete 3D Printing
Fibers 2021, 9(6), 39; https://doi.org/10.3390/fib9060039 - 08 Jun 2021
Cited by 14 | Viewed by 5582
Abstract
The research described in this paper is dedicated to the use of continuous fibers as reinforcement for additive manufacturing, particularly using Shotcrete. Composites and in particular fiber reinforced polymers (FRP) are increasingly present in concrete reinforcement. Their corrosion resistance, high tensile strength, low [...] Read more.
The research described in this paper is dedicated to the use of continuous fibers as reinforcement for additive manufacturing, particularly using Shotcrete. Composites and in particular fiber reinforced polymers (FRP) are increasingly present in concrete reinforcement. Their corrosion resistance, high tensile strength, low weight, and high flexibility offer an interesting alternative to conventional steel reinforcement, especially with respect to their use in Concrete 3D Printing. This paper presents an initial development of a dynamic robot-based manufacturing process for FRP concrete reinforcement as an innovative way to increase shape freedom and efficiency in concrete construction. The focus here is on prefabricated fiber reinforcement, which is concreted in a subsequent additive process to produce load-bearing components. After the presentation of the fabrication concept for the integration of FRP reinforcement and the state of the art, a requirements analysis regarding the mechanical bonding behavior in concrete is carried out. This is followed by a description of the development of a dynamic fiber winding process and its integration into an automated production system for individualized fiber reinforcement. Next, initial tests for the automated application of concrete by means of Shotcrete 3D Printing are carried out. In addition, an outlook describes further technical development steps and provides an outline of advanced manufacturing concepts for additive concrete manufacturing with integrated fiber reinforcement. Full article
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24 pages, 9416 KiB  
Article
Seismic Performance Enhancement of RC Columns Using Thin High-Strength RC Jackets and CFRP Jackets
Fibers 2021, 9(5), 29; https://doi.org/10.3390/fib9050029 - 03 May 2021
Cited by 4 | Viewed by 2937
Abstract
The existing non-ductile RC structures built prior to the 1960s–1970s were mainly conceived to carry only vertical loads. As a result, the columns of these structures demonstrate poor overall hysteresis behavior during strong earthquakes, dominated by brittle shear or/and premature excessive slipping of [...] Read more.
The existing non-ductile RC structures built prior to the 1960s–1970s were mainly conceived to carry only vertical loads. As a result, the columns of these structures demonstrate poor overall hysteresis behavior during strong earthquakes, dominated by brittle shear or/and premature excessive slipping of the inadequately lap-spliced reinforcement. In the present study, the effectiveness of two different strengthening systems (including either the wrapping of the columns by carbon-fiber-reinforced polymer textile or the use of thin high-strength reinforced concrete jackets), was experimentally and analytically investigated. The main variables examined were the strengthening material, the length of the lap splices and the amount of confinement provided by the jackets. Three cantilever column specimens were constructed without incorporating modern design code requirements for preserving seismic safety and structural integrity. Subsequently, the specimens were strengthened and subjected to earthquake-type loading. Their hysteresis performances were compared, while also evaluated with respect to the response of two similar original specimens and the behavior of a control one with continuous reinforcement, tested in a previous study. The predictions of the proposed analytical formulation for the hysteresis behavior of the strengthened specimens were satisfactorily verified by the experimental results. Full article
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15 pages, 5538 KiB  
Article
A New Fabric Reinforced Geopolymer Mortar (FRGM) with Mechanical and Energy Benefits
Fibers 2020, 8(8), 49; https://doi.org/10.3390/fib8080049 - 30 Jul 2020
Cited by 23 | Viewed by 4528
Abstract
A large part of the European building Heritage is dated back over centuries. Consequently, its structural and thermal performances are often inadequate. Commonly, different interventions are proposed for solving these issues separately. However, reasonable drawbacks arise when the structural retrofitting requires a direct [...] Read more.
A large part of the European building Heritage is dated back over centuries. Consequently, its structural and thermal performances are often inadequate. Commonly, different interventions are proposed for solving these issues separately. However, reasonable drawbacks arise when the structural retrofitting requires a direct contact with the target-member while the insulation layer is potentially interposed in between. In this scenario, the present research proposes a novel and unique system able to guarantee both the energetic and the structural retrofitting. Inorganic Matrix Composites (IMCs) are a promising solution in this sense. Among them, the Fabric Reinforced Cementitous Matrix (FRCM) is one of the most used; or rather a composite made of a fabric (open grid or mesh) within an inorganic matrix (lime or cement based). Even if the inorganic matrix has a relevant thickness (if compared with the one of the fabric), its thermal resistance is insufficient. The novelty of this work consists in assessing a new geo-polymeric FRCM-system by combining fly-ash binder (reused material) and expanded glass aggregate (recycled material). Direct tensile tests, for measuring the tensile strength, ultimate strain and elastic modulus, were performed in addition to thermal conductivity tests. The results were compared with those of traditional FRCM (commercially available). The potentiality of the proposal for structural and energy retrofitting is discussed and examples of its possible application are also reported. Full article
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17 pages, 7286 KiB  
Article
Flexural Behavior of High Strength Self-Compacted Concrete Slabs Containing Treated and Untreated Geogrid Reinforcement
Fibers 2020, 8(4), 23; https://doi.org/10.3390/fib8040023 - 13 Apr 2020
Cited by 5 | Viewed by 4222
Abstract
Geogrid is as one of the component materials classified under the geosynthetics used for soil stabilizing and reinforcement. Due to its higher strength-to-weight ratio, ease of handling, and comparatively low costs, geogrid has been gradually explored for possible use in concrete reinforcement. This [...] Read more.
Geogrid is as one of the component materials classified under the geosynthetics used for soil stabilizing and reinforcement. Due to its higher strength-to-weight ratio, ease of handling, and comparatively low costs, geogrid has been gradually explored for possible use in concrete reinforcement. This research aims to assess the feasibility of using geogrids as a possible reinforcement for high-strength self-compacted concrete slabs to provide additional tensile strength and ductility. To enhance the bond between geogrid layers and the cement matrix, two types of geogrid surface modification methods are introduced. Gluing sand to the geogrid surface as a physical surface modification method and immersion in polycarboxylate as a chemical surface modification method are investigated. The effect of geogrid type (uniaxial, biaxial and triaxial) and the number of layers is also introduced. The test results show that the chemical treatment increased the ultimate flexural loading capacity of the tested slab by about 8.5% for one geogrid layer and 13% for two geogrid layers compared to untreated specimens. This work was extended to add two geogrid layers in addition to the slab’s steel reinforcement. The results show that adding geogrid decreased the ultimate flexural loading capacity but significantly increased the slab ductility. Full article
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