Effect of fiber configuration on the fiber-to-mortar bond behaviour (original) (raw)
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Fiber-to-mortar bond behavior in TRM composites: Effect of embedded length and fiber configuration
Composites Part B: Engineering, 2018
The use of Textile Reinforced Mortar (TRM) composites for Externally Bonded Reinforcement (EBR) of reinforced concrete (RC) and masonry structures has attracted several attentions during the last years. The effectiveness of these composites in structural reinforcement is significantly dependent on the TRM-to-substrate and the fiber-to-mortar bond behavior. Despite the importance of the latter, that controls the crack distribution on these composites, have received few attentions and is relatively unknown. This paper presents a combined experimental and analytical study on the effect of fiberembedded length and configuration on the pull-out response. From the obtained results, bond-slip laws are proposed for TRM composites made of unidirectional and bidirectional grids. The tests are performed on a (unidirectional) steel-based and a (bidirectional) glass-based TRM composite as common reinforcing systems. A comparison is also made between the results obtained from single-fiber pull-out tests and conventional single-lap shear bond tests to highlight the differences/similarities between these two test methods.
Single fibre-to-mortar bond characterization in TRM composites
2018
Textile-reinforced mortars (TRM) have been identified as sustainable materials for externally bonded reinforcement (EBR) of masonry and historical structures. The fibre-to-mortar bond, the TRM-to-masonry bond, and the mechanical properties of the TRM constituents have a fundamental role in the performance of this strengthening technique. Although several studies can be found in the literature with the focus on characterization of the tensile response and TRM-to-masonry bond behaviour, the fibre-to-mortar bond response that plays a critical role in the performance of these systems have received few attention. This paper, as an step towards addressing the gap in characterization of the fibre-to-mortar bond behaviour, presents an experimental and analytical investigation on the effect of test setup and fiber embedded length on the pull-out response and bond-slip laws in TRM composites. Three different pull-out test setups, consisting of one pull-pull and two pull-push configurations, are developed and investigated for characterization of the single fibreto-mortar bond behaviour. The experimental and analytical results are discussed and presented and bond-slip laws are extracted for each test setup and embedded length.
Effect of Mortar Age on the Textile-to-Mortar Bond Behavior
XV International Conference on Durability of Building Materials and Components. eBook of Proceedings, 2020
Textile-reinforced mortar (TRM) composites have received extensive attention as a sustainable solution for seismic strengthening of masonry and historical structures. This new system is composed of textile fibers embedded in an inorganic matrix and is applied on the masonry and the concrete substrate surface as an externally bonded reinforcement (EBR) system. The bond at the textile-to-mortar interfaces is the main stress-transfer mechanism and, therefore, should be thoroughly investigated. Furthermore, the effectiveness of TRMs in improving the seismic performance of existing structures is highly dependent on the durability of its components, materials, textile-to-mortar bond, and their long-term behavior. Due to the novelty of these materials in application to masonry structures, several aspects related to the durability and long-term performance of them are still not clear. To that end, a new study has been launched that looks at the time effect on the mechanical properties and bond behavior between fiber and mortar. For this purpose, two different hydraulic lime-based mortars, as well as steel and glass fibers, are used to investigate the effect of mortar age on the TRM system after 180 days. The results show that at the early age of mortars, their mechanical properties, and the bond behavior of textile-to-mortar have been increased. Another critical point to remember is that by increasing the mortar age, textile-to-mortar bond and mortar strength are decreased.
Materials and Structures, 2021
The structural effectiveness of textile reinforced mortar (TRM) composites relies on their load transfer capacity to the substrate and the interaction between textile and mortar. The bond plays a crucial role in mechanism of TRM composites. Despite some recent investigations, a deep understanding still needs to be gained on the textile-to-mortar bond to develop suitable analytical and numerical predictive models, improve test methods, and orient design criteria. This work describes a laboratory study in which pull-out tests were carried out to investigate the effect of the slip rate and cyclic loading on the textile-to-mortar bond behaviour. Alkali-resistant glass fabric and sgalvanised ultra-high tensile strength steel cords embedded in two different lime-based mortars were tested. The pull-out response was sensitive to the strain rate at low rates. Cyclic loading produced a strength degradation, which reduced with the number of cycles.
Textile-to-mortar bond behaviour in lime-based textile reinforced mortars
Construction and Building Materials, 2019
Lime-based textile-reinforced mortars (TRM) have recently found a growing interest for repair and strengthening of masonry and historical structures. Despite extensive experimental and numerical investigations performed in the last years on the performance of these composites, there is still a lack of fundamental understanding of the fabric-to-mortar bond behaviour (as one of the main mechanisms affecting the cracking and nonlinear response of these composites) and the parameters affecting that. This paper, aimed at addressing this gap, presents a comprehensive experimental and analytical investigation on how the test setup, embedded length, load rate, mortar age and fabric configuration affect the bond behaviour in lime-based TRMs. In total 160 pull-out tests are performed on a glass-based and a steel-based TRM commonly used for strengthening of masonry structures. The results contribute to standardization of the test procedures for characterization of the fabric-to-mortar bond behaviour, to fundamental understanding of this mechanism and to optimization of the design of these composites for enhancing their mechanical response.
Journal of Composites for Construction, 2016
Despite the current awareness of the high seismic risk of earthen structures, little has been done so far to develop proper strengthening solutions for the rammed earth heritage. Based on the effectiveness of TRM for masonry buildings, the strengthening of rammed earth walls with externally bonded fibers using earth-based mortar is being proposed as a compatible solution. In this context, the investigation of bond behavior was conducted by means of direct tensile tests, pull-out tests and single lap-shear tests. The specimens were prepared using earth-based mortars and two different types of meshes (glass and nylon) while considering different-bonded lengths. The direct tensile tests on TRM coupons showed the high capacity of the nylon mesh in transferring stresses after cracking of the mortar. The pull-out tests highlighted that in the case of glass fiber mesh, the bond was granted by friction, while the mechanical anchorage promoted by the transversal yarns granted the bond of the nylon mesh. Finally, the single lap-shear tests showed that the adopted earth-based mortar seems to limit the performance of the strengthening.
Bond behaviour in lime-based textile reinforced mortars
CRC Press eBooks, 2020
Application of textile-reinforced mortar (TRM) composites have for strengthening of existing structures or for production of new thin structural elements has attracted a growing recent attention. TRMs are made of continuous fibres (in the form of fabric or mesh) embedded in an inorganic matrix forming a composite material. The large variety of available fabric (glass, steel, basalt, PBO, etc.) and mortar types (cement-based, lime-based, etc.) leads to a wide range of mechanical properties making these composites suit able for fit-for-purpose design applications. Due to mechanical and hygrothermal compatibility issues, limebased TRMs are the preferred choice for application to existing masonry and historical structures. Meanwhile, cement-based TRMs are usually employed for application to existing concrete or new masonry structures. The main characteristic behaviour of these composites is the tension stiffening response and distributed crack ing under tensile loads which are highly influenced by the fabric-to-mortar bond behaviour. Fundamental understanding of this mechanism (the fabric-to-mortar bond behaviour) and parameters affecting that are therefore of critical importance of designing TRM composites with desired properties. This paper presents and overview of the recent studies we performed during the lat years for better udnertanding this mechanism.
Textile-to-mortar bond behavior: An analytical study
Construction and Building Materials, 2021
Reliable design and application of textile-reinforced mortar (TRM) composites for the repair of existing masonry and concrete structures requires a fundamental understanding of the textile-tomortar bond behavior as one of the main mechanisms controlling their nonlinear response and cracking behavior. It means suitable test setups and analytical models are needed to extract the bond-slip laws from the experimental pull-out tests. This paper proposes a new bond-slip law and analytical model, which predicts the bond behavior of lime and cement-based TRM composites considering the slip hardening and softening effects observed in experimental tests. For this purpose, the pull-out response of experimental specimens with different fiber types (steel and glass fibers), bond lengths, and mortar age are analyzed, and their bond slip-laws are extracted. The accuracy of the developed model is shown by comparing the analytical and experimental results.
2019
Due to its low tensile strength and brittle behavior, the use of concrete as structural material has required the use of tensile reinforcement, traditionally on the form of reinforcing bars placed on the locations in which high tensile stresses are expected. In previous decades, the use of steel, glass, or plastic fibers dispersed randomly on the fresh concrete mix for the total or partial replacement of reinforcing bars has shown to provide significant increase on the tensile and flexural strength, abrasion resistance, permeability, toughness and durability of concrete. The use of this composite material, known as fiber reinforced concrete (FRC) or mortar (FRM), for industrial pavement, tunnel linings, and hydraulic and precast structures has shown satisfactory results. More recently, the use of FRC and FRM for the strengthening of existing concrete and masonry structures has caught the attention of researchers worldwide. Unfortunately, experimental evidence on the topic is still s...
MORTAR-BASED SYSTEMS FOR EXTERNALLY BONDED STRENGTHENING OF MASONRY
Mortar-based composite materials appear particularly promising for use as externally bonded reinforcement (EBR) systems for masonry structures. Nevertheless, their mechanical performance, which may significantly differ from that of Fibre Reinforced Polymers, is still far from being fully investigated. Furthermore, standardized and reliable testing procedures have not been defined yet. The present paper provides an insight on experimental-related issues arising from campaigns on mortar-based EBRs carried out by laboratories in Italy, Portugal and Spain. The performance of three reinforcement systems made out of steel, carbon and basalt textiles embedded in inorganic matrices has been investigated by means of uniaxial tensile coupon testing and bond tests on brick and stone substrates. The experimental results contribute to the existing knowledge regarding the structural behaviour of mortar-based EBRs against tension and shear bond stress, and to the development of reliable test procedures aiming at their homogenization/standardization.