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Fiber Reinforced Materials for Buildings Strengthening

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (31 July 2021) | Viewed by 33266

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Special Issue Editors

Prof. Francesco Micelli

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Guest Editor

University of Salento, Lecce, Italy
Interests: structural analysis; structural strengthening; composites; FRP; FRCM/TRM; FRC; confinement; durability; concrete; masonry

Prof. Dr. Maria Antonietta Aiello

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Guest Editor

Department of Engineering for Innovation, University of Salento, Lecce, Italy
Interests: retrofitting of existing RC and masonry structures with innovative materials and systems; seismic vulnerability of structures and non-structural elements; short and long term behavior of structures and structural materials; sustainable structural materials

Special Issue Information

Dear Colleagues,

Fiber-reinforced materials have been extensively studied and used in structural strengthening of civil and heritage buildings over the last two decades. Fiber-reinforced polymer (FRP) composites have been introduced in technical provisions and design guidelines in different countries. More recently, fabric-reinforced mortar (FRCM), textile-reinforced mortar (TRM), and composite-reinforced mortar (CRM) materials have found an interesting field of application in heritage masonry buildings. Moreover, high-performance fiber-reinforced cements (HPFRC) have been studied and applied for the external strengthening of reinforced concrete (RC) buildings. All these materials are grouped in the family of fiber-reinfroced materials, which have opened a new era in structural repair and retrofitting in civil engineering.
Ongoing research and new trends for the structural modeling and applications of such materials may find an ideal placement in this Special Issue. New papers in this field are welcome in order to provide an international forum for scientists, industrial partners, and practitioners to present and discuss the recent advances and future perspectives in the use of fiber-reinforced materials as strengthening systems in civil engineering.
Topics include: bond behavior; codes and design guidelines; concrete-filled FRP tubular members; RC structures reinforced or pre-stressed with FRP; confinement; durability and long-term behavior; field applications and case studies; fire, impact, and blast loading; FRP as internal reinforcement; new fiber reinforced materials and products; seismic retrofit of structures; strengthening of concrete, steel, masonry and timber structures; sustainability; and testing.
It is our pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Francesco Micelli
Prof. Maria Antonietta Aiello
Guest Editors

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Keywords

fibers
strengthening
retrofitting
repair
FRP
TRM
FRCM
HPFRC
confinement
bond
flexure
shear
durability
seismic

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Published Papers (12 papers)

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Research

23 pages, 4130 KiB

Open AccessArticle

Flexural Strength Design of Hybrid FRP-Steel Reinforced Concrete Beams

by Binbin Zhou, Ruo-Yang Wu, Yangqing Liu, Xiaohui Zhang and Shiping Yin

Materials 2021, 14(21), 6400; https://doi.org/10.3390/ma14216400 - 25 Oct 2021

Cited by 11 | Viewed by 3253

Abstract

Through proper arranging of a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and steel bars in the tensile region of the beam, the advantages of both FRP and steel materials can be sufficiently exploited to enhance the flexural capacity and ductility of a concrete beam. In this paper, a methodology for the flexural strength design of hybrid FRP-steel reinforced concrete (RC) beams is proposed. Firstly, based on the mechanical features of reinforcement and concrete and according to the latest codified provisions of longitudinal reinforcement conditions to ensure ductility level, the design-oriented allowable ranges of reinforcement ratio corresponding to three common flexural failure modes are specified. Subsequently, the calculation approach of nominal flexural strength of hybrid FRP-steel RC beams is established following the fundamental principles of equilibrium and compatibility. In addition to the common moderately-reinforced beams, the proposed general calculation approach is also applicable to lightly-reinforced beams and heavily-reinforced beams, which are widely used but rarely studied. Furthermore, the calculation process is properly simplified and the calculation accuracy is validated by the experimental results of hybrid FRP-steel RC beams in the literature. Finally, with the ductility analysis, a novel strength reduction factor represented by net tensile steel strain and reinforcement ratio is proposed for hybrid FRP-steel RC beams. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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18 pages, 2722 KiB

Open AccessArticle

Residual TRM-to-Concrete Bond after Freeze–Thaw Cycles

by Paraskevi D. Askouni and Catherine (Corina) G. Papanicolaou

Materials 2021, 14(18), 5438; https://doi.org/10.3390/ma14185438 - 20 Sep 2021

Cited by 2 | Viewed by 2566

Abstract

In the present work, the effect of various freeze–thaw cycles (namely, 0, 10, 30, 50, 60, and 70) on the residual bond characteristics of textile reinforced mortar (TRM)-to-concrete was experimentally examined. The TRM consisted of a carbon dry fiber textile embedded in a cement-based matrix. Two mortar types were used as the matrix: a normal-weight and a lightweight one sharing the same hydraulic powders but different aggregates (limestone and pumice sand, respectively). The single-lap/single-prism set up was applied after the specimens underwent hygro-thermal treatment (according to ASTM C 666-Procedure B). Failure was due to the sleeve fibers rupturing the load aligned yarns or textile slippage from the mortar for an exposure period ranging between 0 and 60 cycles and to TRM debonding from the substrate for 70 cycles. Increasing cycles resulted in the intensification of partial interlaminar debonding phenomena and the weakening of the textile-to-matrix bond, with lightweight mortar being more prone to these effects. In the absence of a commonly accepted standardized method for the assessment of the freeze–thaw resistance of cement-based composites, the criterion for the termination of the freeze–thaw sequence was the number of cycles inferring a shift in failure mode (from fiber rupture/fiber slippage to TRM debonding from the substrate). Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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18 pages, 8383 KiB

Open AccessArticle

Strengthening of Continuous Reinforced Concrete Deep Beams with Large Openings Using CFRP Strips

by Mohammed Riyadh Khalaf, Ali Hussein Ali Al-Ahmed, Abbas AbdulMajeed Allawi and Ayman El-Zohairy

Materials 2021, 14(11), 3119; https://doi.org/10.3390/ma14113119 - 6 Jun 2021

Cited by 13 | Viewed by 3235

Abstract

To accommodate utilities in buildings, different sizes of openings are provided in the web of reinforced concrete deep beams, which cause reductions in the beam strength and stiffness. This paper aims to investigate experimentally and numerically the effectiveness of using carbon fiber reinforced polymer (CFRP) strips, as a strengthening technique, to externally strengthen reinforced concrete continuous deep beams (RCCDBs) with large openings. The experimental work included testing three RCCDBs under five-point bending. A reference specimen was prepared without openings to explore the reductions in strength and stiffness after providing large openings. Openings were created symmetrically at the center of spans of the other specimens to represent 40% of the overall beam depth. Moreover, finite elements (FE) analysis was validated using the experimental results to conduct a parametric study on RCCDBs strengthened with CFRP strips. The results confirmed reductions in the ultimate load by 21% and 7% for the un-strengthened and strengthened specimens, respectively, due to the large openings. Although the large openings caused reductions in capacities, the CFRP strips limited the deterioration by enhancing the specimen capacity by 17% relative to the un-strengthened one. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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21 pages, 22685 KiB

Open AccessArticle

The Effect of SCMs in Blended Cements on Sorption Characteristics of Superabsorbent Polymers

by Rohollah Rostami, Agnieszka J. Klemm and Fernando C. R. Almeida

Materials 2021, 14(7), 1609; https://doi.org/10.3390/ma14071609 - 25 Mar 2021

Cited by 4 | Viewed by 2121

Abstract

Supplementary cementitious materials (SCMs), such as fly ash (FA) and ground granulated blast-furnace slag (GGBS), are often used as a partial replacement of cements to improve the sustainability of Portland cement-based materials and reduce their environmental impact. Superabsorbent polymers (SAPs) can be successfully used as internal curing agents in ultra-high performance cementitious materials by facilitating the hydration process and controlling the water supply in both fresh and hardened states. This paper intends to characterise the physical and chemical properties of SAPs and their sorption properties in different blended cement environments. The swelling capacity and kinetics of absorption of three superabsorbent polymers with different chemical compositions and grading were tested in different cement environments. Experimental results of their sorption performance in distinct solutions, including deionised water (DI), Portland cement (PC), and blended cements (PC-FA and PC-GGBS) and changes in pH of different solutions over time were investigated. The results showed that PC-FA solution had the lowest pH followed by PC-GGBS solution. Moreover, SAPs samples displayed the highest absorption capacities in PC-FA solutions, and the lowest swelling capacities were found in PC-GGBS solutions. Furthermore, SAP with smaller particle sizes had the greatest absorption capacity values in all solutions. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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20 pages, 4442 KiB

Open AccessArticle

Chloride Diffusion Property of Hybrid Basalt–Polypropylene Fibre-Reinforced Concrete in a Chloride–Sulphate Composite Environment under Drying–Wetting Cycles

by Yang Luo, Ditao Niu and Li Su

Materials 2021, 14(5), 1138; https://doi.org/10.3390/ma14051138 - 28 Feb 2021

Cited by 14 | Viewed by 1930

Abstract

The effect of fibre reinforcement on the chloride diffusion property of concrete is controversial, and the coupling effect of sulphate erosion and drying–wetting cycles in marine environments has been neglected in previous studies. In this study, the chloride diffusion property of hybrid basalt–polypropylene fibre-reinforced concrete subjected to a combined chloride–sulphate solution under drying–wetting cycles was investigated. The effects of basalt fibre (BF), polypropylene fibre (PF), and hybrid BP–PF on the chloride diffusion property were analysed. The results indicate that the presence of sulphate inhibits the diffusion of chloride at the early stage of erosion. However, at the late stage of erosion, sulphate does not only accelerate the diffusion of chloride by causing cracking of the concrete matrix but also leads to a decrease in the alkalinity of the pore solution, which further increases the risk of corrosion of the reinforcing steel. An appropriate amount of fibre can improve the chloride attack resistance of concrete at the early stage. With the increase in erosion time, the fibre effectively prevents the formation and development of sulphate erosion microcracks, thus reducing the adverse effects of sulphate on the resistance of concrete to chloride attack. The effects of sulphate and fibre on the chloride diffusion property were also elucidated in terms of changes in corrosion products, theoretical porosity, and the fibre-matrix interface transition zone. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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18 pages, 3031 KiB

Open AccessArticle

Finite Element Modeling of Bond Behavior of FRP and Steel Plates

by Elena Ciampa, Francesca Ceroni and Maria Rosaria Pecce

Materials 2021, 14(4), 757; https://doi.org/10.3390/ma14040757 - 5 Feb 2021

Cited by 3 | Viewed by 2236

Abstract

Strengthening systems for existing reinforced concrete (RC) structures are increasingly needed due to several problems such as degradation of materials over the time, underdesign, serviceability or seismic upgrading, or new code requirements. In the last decades, strengthening by fibers composite materials applied with various techniques (FRP, FRCM, NSM) were largely investigated and theoretical formulations have been introduced in national and international design guidelines. Although they are an excellent strengthening solution, steel plates may represent still a valid traditional alternative, due to low costs, ductile stress-strain behavior, simple and fast mounting with possibility of reusing the material. Guidelines for a correct design are still lack and, therefore, detailed models and design formulas are needed. In this paper, the bond behavior at the plate-concrete interface, which plays a key role for the effectiveness of the strengthening system, is analyzed by means of 3D finite element models calibrated on experimental results available in literature. Parametric analyses were carried out by changing some meaningful parameters. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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17 pages, 3553 KiB

Open AccessFeature PaperArticle

Constitutive Models for the Tensile Behaviour of TRM Materials: Literature Review and Experimental Verification

by Maria Concetta Oddo, Giovanni Minafò and Lidia La Mendola

Materials 2021, 14(3), 700; https://doi.org/10.3390/ma14030700 - 2 Feb 2021

Cited by 8 | Viewed by 2469

Abstract

In recent years, the scientific community has focused its interest on innovative inorganic matrix composite materials, namely TRM (Textile Reinforced Mortar). This class of materials satisfies the need of retrofitting existing masonry buildings, by keeping the compatibility with the substrate. Different recent studies were addressed to improve the knowledge on their mechanical behaviour and some theoretical models were proposed for predicting the tensile response of TRM strips. However, this task is complex due to the heterogeneity of the constituent materials and the stress transfer mechanism developed between matrix and fabric through the interface in the cracked stage. This paper presents a state-of-the-art review on the existing constitutive models for the tensile behavior of TRM composites. Literature experimental results of tensile tests on TRM coupons are presented and compared with the most relevant analytical models proposed until now. Finally, a new experimental study is presented and its results are used to further verify the reliability of the literature expressions. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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18 pages, 4865 KiB

Open AccessArticle

Finite Element Analysis of Axial Compression Steel Members Strengthened with Unbonded CFRP Laminates

by Fengky Satria Yoresta, Phan Viet Nhut and Yukihiro Matsumoto

Materials 2020, 13(16), 3540; https://doi.org/10.3390/ma13163540 - 11 Aug 2020

Cited by 5 | Viewed by 3265

Abstract

This paper presented a non-linear finite element (FE) analysis to investigate the potential of unbonded carbon fiber-reinforced polymers (CFRP) strengthening in improving the axial compression performance of steel members. The FE model was firstly developed and validated against experimental works. Four parameters considered in the parametric study were the number of CFRP layers, CFRP length, slenderness ratio, and elastic modulus of CFRP. It was confirmed that the unbonded CFRP strengthening method is effective at enhancing the load-carrying capacity as well as delaying the overall buckling of the axial steel members. The strength increase is highly affected by the first three parameters. In addition, the method of an equivalent slenderness ratio can be used for strength design. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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18 pages, 8387 KiB

Open AccessArticle

Mechanical Properties of Carbon-Fabric-Reinforced High-Strength Matrices

by Bekir Yılmaz Pekmezci and Ali Çopuroğlu

Materials 2020, 13(16), 3508; https://doi.org/10.3390/ma13163508 - 9 Aug 2020

Cited by 6 | Viewed by 2378

Abstract

Fabric-reinforced cementitious matrices (FRCM) are promising technologies that respond to today’s architectural approaches. However, due to their high strength and ductility, they are starting to be implemented in buildings as strengthening systems. In this experimental study, the amount of fiber along the load direction in high-strength cementitious matrices and the effects of the fiber orientation on FRCM mechanical properties were studied. A total of four different composites were produced with two fabrics and two matrices. Tensile and flexural tests were carried out on composites. Within the scope of microstructure studies, scanning electron microscope micrographs were obtained and analyzed, along with microtopography sections. The main result obtained from the study indicates that as the fiber area in the direction of the load increases, the load order carried in this direction increases. However, this increase does not have to be proportional to the fiber area used in the direction of the load. The fiber coating and coating matrix interface play important roles in a composite’s performance. The carbon fibers can be used more efficiently by using them along the load direction and the loads in the matrix can be transferred to the carbon fibers by creating a larger fiber–matrix interface area. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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16 pages, 6410 KiB

Open AccessArticle

Properties of Alkali-Resistant Glass Fiber Reinforced Coral Aggregate Concrete

by Shutong Yang, Miao Yu, Kun Dong and Yushan Yang

Materials 2020, 13(16), 3450; https://doi.org/10.3390/ma13163450 - 5 Aug 2020

Cited by 20 | Viewed by 3145

Abstract

The intention of this paper is to analyze the properties of coral aggregate concrete (CAC) that is reinforced by alkali-resistant glass fibers (ARGF) and the bond performance with BFRP (basalt fiber reinforced polymer) bars. Two types of ARGF, denoted by Type A and Type B with different manufacturing technologies and fiber lengths, are used in the test. Tests of compressive strength, splitting tensile strength, and flexural performance were performed on ARGF-CAC with four different contents for the two types of ARGF. It is found that the cubic compressive strength is slightly reduced when the fiber volume fraction exceeds 0.5%, but almost keeps invariable if the fiber content further increases. However, the tensile strength, residual strength retention and flexural toughness are improved as more ARGFs are added into CAC, and even higher with Type B ARGF addition. The optimized volume fraction is 1.5% for both the two types of ARGF based on the evaluation of the workability and mechanical performance. Moreover, central pull-out test was performed to study the bond properties of ARGF-CAC with BFRP bars. It is found that both the maximum average bond stress and residual frictional stress are generally reduced as the bond length is longer. The addition of Type B ARGFs can significantly improve the bond strength; however, the Type A ARGFs seem to have marginal effect. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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18 pages, 6995 KiB

Open AccessArticle

Flexural Behavior of Fire-Damaged Prefabricated RC Hollow Slabs Strengthened with CFRP versus TRM

by Zheng-Ang Sui, Kun Dong, Jitong Jiang, Shutong Yang and Kexu Hu

Materials 2020, 13(11), 2556; https://doi.org/10.3390/ma13112556 - 4 Jun 2020

Cited by 9 | Viewed by 2273

Abstract

In this paper, carbon fiber reinforced polymer (CFRP) and textile reinforced mortar (TRM) strengthening techniques were proposed to retrofit and strengthen fire-damaged prefabricated concrete hollow slabs. A total of six slabs, from an actual multi-story masonry building, were tested to investigate the flexural performance of reinforced concrete (RC) hollow slabs strengthened with TRM and CFRP. The investigated parameters included the strengthening method (CFRP versus TRM), the number of CFRP layers, and with or without fire exposure. One unstrengthened slab and one TRM strengthened slab served as the control specimens without fire exposure. The remaining four slabs were first exposed to ISO-834 standard fire for 1 h, and then three of them were strengthened with CFRP or TRM. Through the four-point bending tests at ambient temperature, the failure modes, load and deformation response were recorded and discussed. Both CFRP and TRM strengthening methods can significantly increase the cracking load and peak load of the fire-damaged hollow slabs, as well as the stiffness in the early stage. The prefabricated hollow slabs strengthened by CFRP have better performance in the ultimate bearing capacity, but the ductility reduced with the increase of CFRP layers. Meanwhile, the TRM strengthening technique is a suitable method for the performance improvement of fire-damaged hollow slabs, in terms of not only the load capacity, especially the cracking load, but also the flexural stiffness and deformation capacity. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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15 pages, 2661 KiB

Open AccessArticle

Fatigue Behavior of PBO FRCM Composite Applied to Concrete Substrate

by Angelo Savio Calabrese, Tommaso D’Antino, Pierluigi Colombi, Christian Carloni and Carlo Poggi

Materials 2020, 13(10), 2368; https://doi.org/10.3390/ma13102368 - 21 May 2020

Cited by 18 | Viewed by 2567

Abstract

Several reinforced-concrete (RC) structural elements are subjected to cyclic load, such those employed in highway and railroad bridges and viaducts. The durability of these elements may be reduced as a consequence of fatigue, which mainly affects the steel reinforcement. The use of externally bonded (EB) fiber-reinforced cementitious matrix (FRCM) composites allows the moment capacity to be shared by the internal reinforcement and the EB composite, thus increasing the fatigue life of the strengthened RC member. The effectiveness of EB FRCM composites is related to the composite bond properties. However, limited research is currently available on the effect of fatigue on the bond behavior of FRCM-substrate joints. This study provides first the state of the art on the fatigue behavior of different FRCM composites bonded to a concrete substrate. Then, the fatigue bond behavior of a polyparaphenylene benzo-bisoxazole (PBO) FRCM is experimentally investigated using a modified beam test set-up. The use of this set-up provided information on the effect of fiber-matrix interface shear and normal stresses on the specimen fatigue bond behavior. The results showed that fatigue loading may induce premature debonding at the matrix-fiber interface and that stresses normal to the interface reduce the specimen fatigue life. Full article

(This article belongs to the Special Issue Fiber Reinforced Materials for Buildings Strengthening)

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