Research

12 pages, 3012 KiB

Open AccessArticle

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 - 02 Apr 2024

Viewed by 539

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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18 pages, 3947 KiB

Open AccessArticle

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

Viewed by 559

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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23 pages, 2666 KiB

Open AccessArticle

Design of Strain-Hardening Natural TRM Composites: Current Challenges and Future Research Paths

by Rogiros Illampas, Daniel V. Oliveira and Paulo B. Lourenço

Materials 2023, 16(13), 4558; https://doi.org/10.3390/ma16134558 - 24 Jun 2023

Cited by 1 | Viewed by 1394

Abstract

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that [...] Read more.

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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14 pages, 2085 KiB

Open AccessEditor’s ChoiceArticle

Numerical Modelling of the Constitutive Behaviour of FRCM Composites through the Use of Truss Elements

by Maria Concetta Oddo, Giovanni Minafó, Marielisa Di Leto and Lidia La Mendola

Materials 2023, 16(3), 1011; https://doi.org/10.3390/ma16031011 - 22 Jan 2023

Cited by 2 | Viewed by 1314

Abstract

The modeling of the mechanical behavior of Fabric Reinforced Cementitious Matrix (FRCM) composites is a difficult task due to the complex mechanisms established at the fibre-matrix and composite-support interface level. Recently, several modeling approaches have been proposed to simulate the mechanical response of [...] Read more.

The modeling of the mechanical behavior of Fabric Reinforced Cementitious Matrix (FRCM) composites is a difficult task due to the complex mechanisms established at the fibre-matrix and composite-support interface level. Recently, several modeling approaches have been proposed to simulate the mechanical response of FRCM strengthening systems, however a simple and reliable procedure is still missing. In this paper, two simplified numerical models are proposed to simulate the tensile and shear bond behavior of FRCM composites. Both models take advantage of truss and non-linear spring elements to simulate the material components and the interface. The proposed approach enables us to deduce the global mechanical response in terms of stress-strain or stress-slip relations. The accuracy of the proposed models is validated against the experimental benchmarks available in the literature. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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19 pages, 5726 KiB

Open AccessArticle

Experimental Characterisation of Lime-Based Textile-Reinforced Mortar Systems Made of Either Jute or Flax Fabrics

by Marco Pepe, Rosario Lombardi, Giuseppe Ferrara, Stefano Agnetti and Enzo Martinelli

Materials 2023, 16(2), 709; https://doi.org/10.3390/ma16020709 - 11 Jan 2023

Cited by 3 | Viewed by 1449

Abstract

Existing buildings are often in need of strengthening interventions, and several technical solutions have been recently developed for this purpose. Among them, the use of textile-reinforced mortar (TRM) composites has gained consensus as a technically viable and economically convenient option. Moreover, TRM has [...] Read more.

Existing buildings are often in need of strengthening interventions, and several technical solutions have been recently developed for this purpose. Among them, the use of textile-reinforced mortar (TRM) composites has gained consensus as a technically viable and economically convenient option. Moreover, TRM has the potential to be employed as a reversible and sustainable strengthening technique for masonry buildings. In this context, the present paper aims to investigate the mechanical properties of TRM systems consisting of sustainable phases, such as lime-based matrices and natural fabrics produced by waiving fibers obtained from plants, such as Jute or Flax. This class composite system can be referred to as natural TRM and is denoted by the acronym NTRM. The present study moves from the geometric and mechanical characterisation of fibres and fabrics and, after having also investigated the properties of the mortar, it reports the results of tensile tests carried out on specimens of the NTRM systems under consideration, with the main aim of providing the empirical bases of the relationships between the geometric and physical properties of the constituents and the resulting mechanical response of the composite system. The obtained results show that the considered Flax-TRM system has an apparent composite behavior, as its response to tension is clearly characterised by the well-known three stages corresponding to the elastic response, the formation of cracks, and the reinforcement response up to rupture. Conversely, the Jute-TRM system needs to be further improved in terms of balance between the properties of the matrix and the internal reinforcement. Further studies will be devoted to this specific aspect and, more generally, to investigating the relationships between constituents’ properties and the NTRM behavior. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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16 pages, 5626 KiB

Open AccessEditor’s ChoiceArticle

Theoretical Modelling of the Degradation Processes Induced by Freeze–Thaw Cycles on Bond-Slip Laws of Fibres in High-Performance Fibre-Reinforced Concrete

by Rosa Penna, Luciano Feo, Enzo Martinelli and Marco Pepe

Materials 2022, 15(17), 6122; https://doi.org/10.3390/ma15176122 - 03 Sep 2022

Cited by 6 | Viewed by 1139

Abstract

High-performance fibre-reinforced concrete (HPFRC) is a composite material in which the advantages of fibre-reinforced concrete (FRC) are combined with those of a high-performance concrete (HPC), which mitigates the weaknesses of conventional concrete and improves its overall performance. With the aim to reduce the [...] Read more.

High-performance fibre-reinforced concrete (HPFRC) is a composite material in which the advantages of fibre-reinforced concrete (FRC) are combined with those of a high-performance concrete (HPC), which mitigates the weaknesses of conventional concrete and improves its overall performance. With the aim to reduce the long-term maintenance costs of structures, such as heavily loaded bridges, HPFRC is highly recommended due to its major durability performance. Specifically, its good antifreezing property makes it suitable for application in cold regions where cyclic freeze–thaw conditions cause the concrete to degrade. In this paper, a numerical simulation of the degradation processes induced by freeze–thaw cycles on bond-slip laws in HPFRC beam specimens has been developed so as to assess their effect on the flexural response of specimens as the fibres’ volume percentage changes. Their cracking strength, postcracking strength, and toughness were predicted, with the present model being able to predict the cracking strength, postcracking strength and toughness of the HPFRC beam element under bending load conditions. Its accuracy was confirmed by comparing the model predictions with experimental results. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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19 pages, 6085 KiB

Open AccessArticle

Development in Sustainable Concrete with the Replacement of Fume Dust and Slag from the Steel Industry

by Maria Eugenia Parron-Rubio, Benaissa Kissi, Francisca Perez-García and Maria Dolores Rubio-Cintas

Materials 2022, 15(17), 5980; https://doi.org/10.3390/ma15175980 - 29 Aug 2022

Cited by 3 | Viewed by 1402

Abstract

Nowadays, the reuse of waste is a challenge that every country in the world is facing in order to preserve the planet and introduce a circular economy. The chemical composition of some steel waste suggests that there are potentially appropriate substances for reuse, [...] Read more.

Nowadays, the reuse of waste is a challenge that every country in the world is facing in order to preserve the planet and introduce a circular economy. The chemical composition of some steel waste suggests that there are potentially appropriate substances for reuse, since this type of slag undergoes a process similar to that of cement in its manufacture. The advantages for the environment are obvious, as it valorises waste that is deposited in landfills. This paper studies the field of stainless steel, because its composition is different from that of carbon steel, and the replacement of cement with material or waste produced in the manufacture of stainless steel in a concrete matrix. This paper presents the results of replacing 25% of cement with material or waste produced in the manufacture of stainless steel in a concrete matrix whose values in the substitutions carried out were around 21% and 25% in terms of increased resistance capacity. These results have been obtained by carrying out tests, in terms of both strength and environmental capacity, allowing us to determine viable applications for the use of steel waste to improve the performance of cement or at least match it. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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15 pages, 6122 KiB

Open AccessArticle

Mechanical Properties of Hybrid PVA–Natural Curaua Fiber Composites

by Bartosz Zukowski, Yasmim Gabriela dos Santos Mendonça, Igor José Koury Tavares and Romildo Dias Toledo Filho

Materials 2022, 15(8), 2808; https://doi.org/10.3390/ma15082808 - 11 Apr 2022

Cited by 3 | Viewed by 1510

Abstract

This work presents the experimental study of hybrid cement-based composites with polyvinyl alcohol fiber (PVA) and alkali-treated, short, natural curaua fiber. The objective of this research is to develop composites reinforced with PVA and curaua fiber to present strain-hardening behavior with average crack [...] Read more.

This work presents the experimental study of hybrid cement-based composites with polyvinyl alcohol fiber (PVA) and alkali-treated, short, natural curaua fiber. The objective of this research is to develop composites reinforced with PVA and curaua fiber to present strain-hardening behavior with average crack width control. To achieve this objective, three groups of composites were investigated. The first group had only PVA fiber in volumes of 0.5, 1, and 2%. The composite with 2% PVA fiber was the only one with strain-hardening and crack width control. The second group had 0.5% PVA fiber and volume fractions of 2, 2.5, and 3% curaua fiber, and presented only deflection-hardening behavior. The third group had 1% PVA and volumes of 1, 1.5, and 2% curaua fiber, and presented strain-hardening behavior. Based on the results, the hybrid combination of 1% PVA and 1.5% curaua was the optimal mixture as it presented strain-hardening behavior and crack width control, with a lower volume of synthetic PVA fiber. Additionally, compressive strength and mix workability were calculated for the investigated composites for comparison. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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