Research on the Performance of Non-metallic Reinforced Concrete

A special issue of Buildings (ISSN 2075-5309). This special issue belongs to the section "Building Materials, and Repair & Renovation".

Deadline for manuscript submissions: closed (15 November 2023) | Viewed by 21571

Special Issue Editors


E-Mail Website
Guest Editor
CARBOCON GMBH, Ammonstraße 72, 01067 Dresden, Germany
Interests: reinforced concrete; non-metallic reinforcement; strengthening of existing structures

E-Mail Website
Guest Editor
Institute of Concrete Structures, Technische Universität Dresden, 01219 Dresden, Germany
Interests: civil engineering; reinforced concrete; textile reinforced concrete; carbon reinforced concrete

Special Issue Information

Dear Colleagues,

The climate crisis is the main challenge of our time. To reduce the global CO2 emission drastically, the building industry has to change. More than 50% of total CO2 emissions can be traced back to the construction industry. There are many different possible ways available to reduce global CO2 emissions. A prominent potential solution is to avoid demolition and preserve existing buildings by strengthening or retrofitting those structures, e. g. with resource-efficient methods. Another solution is the use of innovative and non-corrosive materials for concrete structures for new buildings.

To reduce the global CO2 emissions effectively, better and more resource-efficient solutions for concrete structures in both potential construction fields (strengthening of existing structures and building new) are necessary.

Therefore, the main aim of this Special Issue is to explore the recent challenges, potentials and developments of innovative concrete structures for more resource-efficient buildings. Potential topics include, but are not limited to:

  • Non-metallic reinforcement
  • Carbon-reinforced concrete
  • Textile-reinforced concrete
  • Strengthening methods of concrete structures
  • Pre-stressed non-metallic reinforcement
  • Practical examples of resource-efficient concrete structures
  • New research fields of concrete structures

Prof. Dr. Alexander Schumann
Dr. Frank Schladitz
Guest Editors

Manuscript Submission Information

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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. Buildings 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 2600 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

  • reinforced concrete
  • non-metallic reinforcement
  • innovative structures
  • new structures
  • strengthening and repair
  • carbon-reinforced concrete
  • textile-reinforced concrete

Published Papers (19 papers)

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Research

13 pages, 6856 KiB  
Article
High-Temperature Behavior of Carbon Reinforced Concrete
by Daniel Ehlig, Alexander Schumann and Lutz Nietner
Buildings 2024, 14(2), 364; https://doi.org/10.3390/buildings14020364 - 29 Jan 2024
Viewed by 609
Abstract
Carbon reinforced concrete is perceived by industry as a promising alternative to the currently established construction products. Previous building authority approvals and approvals for this construction method largely exclude questions of preventive fire protection with regard to load-bearing behavior under fire because there [...] Read more.
Carbon reinforced concrete is perceived by industry as a promising alternative to the currently established construction products. Previous building authority approvals and approvals for this construction method largely exclude questions of preventive fire protection with regard to load-bearing behavior under fire because there are hardly any reliable research results available in this field. This article shows the results of experimental investigations including thermogravimetric analyses of carbon reinforcement and tensile tests on the composite material carbon reinforced concrete. The thermogravimetric analyses show the loss of mass of the carbon reinforcement under a temperature load. A decomposition of the coating system of the carbon fibers and, with increasing temperature load, also of the carbon was observed. By varying various boundary conditions, such as the heating rate and the oxygen content present, their influences can be assessed. Stationary and non-stationary tensile tests on strip-shaped carbon reinforced concrete specimens were used to determine the load-bearing and deformation behavior in the high-temperature range up to 700 °C. The investigations were carried out under constant heating rates of 2 K/min and 10 K/min. This made it possible to obtain stress-strain curves and information on the various temperature-dependent deformation components from mechanical strains and load-independent strains. The time- and temperature-dependent decomposition of the carbon resulted in a reduction in the tensile load-bearing capacity of the reinforcement in the high-temperature range. This effect can be taken into account by considering the cross-sectional loss of the carbon reinforcement in a hot design. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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21 pages, 9392 KiB  
Article
Bio-Inspired Impregnations of Carbon Rovings for Tailored Bond Behavior in Carbon Fiber Reinforced Concrete
by Toni Utech, Tobias Neef, Viktor Mechtcherine and Christina Scheffler
Buildings 2023, 13(12), 3102; https://doi.org/10.3390/buildings13123102 - 14 Dec 2023
Cited by 1 | Viewed by 880
Abstract
Nature provides various templates for integrating organic and inorganic materials to create high-performance composites. Biological structures such as nacre and the structural elements of the glass sponge are built up in layers, leading to remarkable fracture toughness. In this work, the brick-and-mortar and [...] Read more.
Nature provides various templates for integrating organic and inorganic materials to create high-performance composites. Biological structures such as nacre and the structural elements of the glass sponge are built up in layers, leading to remarkable fracture toughness. In this work, the brick-and-mortar and layer-by-layer structures found in these biological examples have been abstracted and implemented by using an aqueous polymer dispersion in combination with nanoclay particles and sodium water glass. These dispersions were used as impregnation of carbon rovings in order to form bio-inspired contact zones towards the concrete matrix. The bonding behavior was investigated using the Yarn Pull-Out (YPO) test, and a beneficial behavior of the layered polymer–nanoclay dispersions was observed. Thermogravimetric analysis (TGA) was used to determine the organic impregnation content of the roving. Further, light microscopy of the roving cross-sections prior to YPO and visual analyses of the fractured contact zone of split concrete specimens provided information on the quality of the impregnation and the interaction with the concrete matrix. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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18 pages, 7000 KiB  
Article
Experimental Investigations of the Bond Behavior between Carbon Rebars and Concrete in Germany
by Alexander Schumann, Sebastian May, Maximilian May, Elisabeth Schütze, Frank Schladitz and Daniel Ehlig
Buildings 2023, 13(12), 2932; https://doi.org/10.3390/buildings13122932 - 24 Nov 2023
Viewed by 697
Abstract
In this paper, we address the relatively underexplored topic of the bond behavior between various carbon rebars and high-strength concrete. This research aims to bridge the knowledge gap in understanding how different manufacturing processes and surface profiles of carbon fiber rods influence their [...] Read more.
In this paper, we address the relatively underexplored topic of the bond behavior between various carbon rebars and high-strength concrete. This research aims to bridge the knowledge gap in understanding how different manufacturing processes and surface profiles of carbon fiber rods influence their bond strength with concrete. Through experimental bond tests comparing different carbon fiber rebars with varied surface profiles and manufacturing methods, we observed that the achievable bond stresses are significantly influenced by these factors. One carbon rebar variant was selected based on preliminary investigations for detailed analysis. Extensive investigations were conducted on the preferred carbon rebar. Factors such as concrete strength, bond length, and testing speed were experimentally explored. The results not only corroborate many findings from traditional reinforced concrete construction but also reveal new phenomena unique to carbon rebars. These insights are crucial for advancing the application of carbon rebars in modern construction, offering a potential solution to challenges faced in conventional concrete construction. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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16 pages, 6573 KiB  
Article
Digital Prefabrication of Lightweight Building Elements for Circular Economy: Material-Minimised Ribbed Floor Slabs Made of Extruded Carbon Reinforced Concrete (ExCRC)
by Sven Bosbach, Matthias Kalthoff, Cynthia Morales Cruz, Viviane Adam, Thomas Matschei and Martin Classen
Buildings 2023, 13(12), 2928; https://doi.org/10.3390/buildings13122928 - 23 Nov 2023
Viewed by 1672
Abstract
To reduce resource consumption and the carbon footprint of the construction industry, new construction principles that stipulate the minimisation of materials are urgently needed. Floor slabs show high potential for saving materials and CO2 emissions, as they account for around 50% of [...] Read more.
To reduce resource consumption and the carbon footprint of the construction industry, new construction principles that stipulate the minimisation of materials are urgently needed. Floor slabs show high potential for saving materials and CO2 emissions, as they account for around 50% of the total volume of concrete used worldwide. A promising approach is the use of corrosion-resistant carbon fibre-reinforced polymer (CFRP) reinforcement, which requires only a small concrete cover to meet bond requirements. Regarding the component’s topology, material-efficient ribbed or waffle slabs have been built for decades but their execution has declined owing to their labour-intense production, which calls for manual installation of the formwork. A recently proposed extrusion manufacturing process combines both approaches for material-minimised construction and allows the fast and formwork-free production of carbon reinforced concrete (CRC) components. This article describes the concept, the finding of the form, fabrication and experimental testing of an innovative ribbed floor slab composed of precast extruded carbon reinforced concrete (ExCRC) webs. The novel floor slab consists of a conventionally cast thin-walled top slab and shaped, load-adapted ExCRC webs to achieve high utilisaton of the structural member. The ribbed slab provides a lightweight structural system with drastic savings in dead load compared with a conventional steel reinforced slab. In addition, the high durability and service life of the novel floor slabs makes them ideal components to be recovered after an initial life cycle and to be re-used in new construction projects. The paper gives an outlook to the full-scale production of one-way and two-way slab systems made of ExCRC such as ribbed slabs, waffle slabs and sandwich slabs with a honeycomb infill. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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12 pages, 4201 KiB  
Article
Contribution of Carbon Concrete Construction to the Circular and Resource Economy
by Jan Kortmann and Stefan Minar
Buildings 2023, 13(11), 2851; https://doi.org/10.3390/buildings13112851 - 14 Nov 2023
Cited by 1 | Viewed by 877
Abstract
Fibre-reinforced composites are used in many industries. In the construction industry, for example, the building material carbon concrete is increasingly being used successfully. Although the demand for fibre-reinforced composites and fibre-reinforced plastics made of carbon fibres has risen continuously by approximately 11% per [...] Read more.
Fibre-reinforced composites are used in many industries. In the construction industry, for example, the building material carbon concrete is increasingly being used successfully. Although the demand for fibre-reinforced composites and fibre-reinforced plastics made of carbon fibres has risen continuously by approximately 11% per year over the last 10 years, there is currently still no coherent integration of fibre-containing waste into the corresponding material cycles. In addition, there are ever-increasing requirements for environmental and climate protection, which necessitate a transformation from linear waste management to a cycle-oriented recycling and resource management overall. Carbon concrete construction is already providing an important impetus for the construction industry. The use of reinforcement made of mat or grid-shaped and bar-shaped carbon fibres basically makes a significant contribution to the conservation of resources, and ultimately a reduction in CO2 emissions of up to 80% is possible. In connection with recyclability, it is demonstrated that with today’s common facilities, both the deconstruction and dismantling of components and structures made of carbon concrete and the collection and sorting of the demolition material using camera-based sorting with a grade purity of 98% are already possible. In addition, the article provides an outlook on the project WIRreFa|WIR! recyceln Fasern (We recycle fibres) and its approach to closing the material cycle of fibre composites. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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20 pages, 8827 KiB  
Article
Investigations into the Shear Load-Capacity of Strengthened Reinforced Concrete Structures with Carbon-Reinforced Concrete
by Sebastian May and Alexander Schumann
Buildings 2023, 13(11), 2765; https://doi.org/10.3390/buildings13112765 - 1 Nov 2023
Viewed by 1083
Abstract
As part of the experiments, 4-point-bending tests to investigate the shear capacity of strengthened T-beams were carried out. Thereby, 5 reference beams and 25 T-beams with carbon reinforced concrete strengthening were tested. Two different impregnated carbon grids in various strengthening configurations at the [...] Read more.
As part of the experiments, 4-point-bending tests to investigate the shear capacity of strengthened T-beams were carried out. Thereby, 5 reference beams and 25 T-beams with carbon reinforced concrete strengthening were tested. Two different impregnated carbon grids in various strengthening configurations at the beams’ webs were checked. The number of strengthening layers was varied as well as the orientation of the grid in the strengthening layer. Furthermore, the influence of pre-damage of the RC beam before strengthening and two different shear slendernesses were investigated. A load increase of 25% to 42% compared to the unstrengthened reference specimens demonstrates the capability of carbon concrete for shear strengthening. In addition to the presentation of tested large-scale specimens, a test analysis will also be conducted, along with the derivation of a limit value for the maximum possible strengthening ratio using carbon-reinforced concrete based on the observed failure modes. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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17 pages, 6951 KiB  
Article
Robot-Assisted Manufacturing Technology for 3D Non-Metallic Reinforcement Structures in the Construction Applications
by Danny Friese, Lars Hahn, Hung Le Xuan, Johannes Mersch, Tobias Neef, Viktor Mechtcherine and Chokri Cherif
Buildings 2023, 13(11), 2748; https://doi.org/10.3390/buildings13112748 - 31 Oct 2023
Viewed by 1030
Abstract
Of all industrial sectors, the construction industry accounts for about 37% of carbon dioxide (CO2) emissions. This encompasses the complete life cycle of buildings, from the construction phase to service life to component disposal. The main source of emissions of climate-damaging [...] Read more.
Of all industrial sectors, the construction industry accounts for about 37% of carbon dioxide (CO2) emissions. This encompasses the complete life cycle of buildings, from the construction phase to service life to component disposal. The main source of emissions of climate-damaging greenhouse gases such as CO2, with a share of 9% of global emissions, is the production of ordinary cement as the main binder of concrete. The use of innovative approaches such as impregnated carbon yarns as non-corrosive reinforcement embedded in concrete has the potential to dramatically reduce the amount of concrete required in construction, since no excessive concrete cover is needed to protect against corrosion, as is the case with steel reinforcement. At the same time, architectural design options are expanded via this approach. This is achieved above all using novel robotic manufacturing technologies to enable no-cut direct fiber placement. This innovative technological approach to fabricating 2D and 3D biologically inspired textiles, including non-metallic structures for textile-reinforced concrete (TRC) components, will promote an automatable construction method that reduces greenhouse gas emissions. Furthermore, the impregnated yarn which is fabricated enables the production of load-adapted and gradual non-metallic reinforcement components. Novel and improved design strategies with innovative reinforcement patterns allow the full mechanical potential of TRC to be realized. The development of a robotic fabrication technology has gone beyond the state of the art to implement spatially branched, biologically inspired 3D non-metallic reinforcement structures. A combined robotic fabrication technology, based on the developed flexible 3D yarn-guiding and impregnation module and a 3D yarn fixation module, is required to implement this sophisticated approach to fabricate freely formed 3D non-metallic reinforcement structures. This paper presents an overview of the development process of the innovative technological concept. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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17 pages, 14967 KiB  
Article
Classification of Multiaxial Behaviour of Fine-Grained Concrete for the Calibration of a Microplane Plasticity Model
by Peter Betz, Verena Curosu, Stefan Loehnert, Steffen Marx and Manfred Curbach
Buildings 2023, 13(11), 2704; https://doi.org/10.3390/buildings13112704 - 26 Oct 2023
Cited by 1 | Viewed by 704
Abstract
Fine-grained high-strength concrete has already been tested extensively regarding its uniaxial strength. However, there is a lack of research on the multiaxial performance. In this contribution, some biaxial tests are investigated in order to compare the multiaxial load-bearing behaviour of fine-grained concretes with [...] Read more.
Fine-grained high-strength concrete has already been tested extensively regarding its uniaxial strength. However, there is a lack of research on the multiaxial performance. In this contribution, some biaxial tests are investigated in order to compare the multiaxial load-bearing behaviour of fine-grained concretes with that of high-strength concretes with normal aggregate from the literature. The comparison pertains to the general biaxial load-bearing behaviour of concrete, the applicability of already existing fracture criteria and the extrapolation for the numerical investigation. This provides an insight into the applicability of existing data for the material characterisation of this fine-grained concrete and, in particular, to compensate for the lack of investigations on fine-grained concretes in general. It is shown, that the calibration of material models for fine-grained concretes based on literature results or normal-grained concrete with similar strength capacity is possible, as long as the uniaxial strength values and the modulus of elasticity are known. For the numerical simulation, a Microplane Drucker–Prager cap plasticity model is introduced and fitted in the first step to the biaxial compression tests. The model parameters are set into relation with the macroscopic quantities, gained from the observable behaviour of the concrete under uniaxial and biaxial compressive loading. It is shown that the model is able to capture the yielding and hardening effects of fine-grained high-strength concrete in different directions. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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25 pages, 27348 KiB  
Article
Damage Analysis and Quality Control of Carbon-Reinforced Concrete Beams Based on In Situ Computed Tomography Tests
by Frank Liebold, Franz Wagner, Josiane Giese, Szymon Grzesiak, Christoph de Sousa, Birgit Beckmann, Matthias Pahn, Steffen Marx, Manfred Curbach and Hans-Gerd Maas
Buildings 2023, 13(10), 2669; https://doi.org/10.3390/buildings13102669 - 23 Oct 2023
Cited by 1 | Viewed by 1279
Abstract
Carbon-reinforced concrete (CRC) is increasingly utilized in construction, due to its unique properties, such as corrosion resistance, high-tensile strength, and durability. Understanding its behavior under different loads is crucial to ensuring its safe and effective use in various construction applications. In this study, [...] Read more.
Carbon-reinforced concrete (CRC) is increasingly utilized in construction, due to its unique properties, such as corrosion resistance, high-tensile strength, and durability. Understanding its behavior under different loads is crucial to ensuring its safe and effective use in various construction applications. In this study, three-point bending tests were performed in combination with large-scale in situ computed tomography (CT). This paper presents the related three- and four-dimensional evaluation methods, with emphasis on crack width and quality control. The focus was on large CRC beams, with cross-sectional sizes of up to 80 mm by 160 mm. Such dimensions require extremely high energy during a CT scan. Therefore, a new experimental setup with energies of up to 8 MeV was used in this study. However, such high energies posed new challenges to the analysis methods. Therefore, two methods (digital volume correlation and grayscale profile analysis) for accurate crack width estimation were adapted and applied to the 3D reconstructions. In addition, a photogrammetric stereo image sequence was acquired and analyzed, using digital image correlation to cross-validate the results derived from the 3D crack width estimates. The 3D CT images also played a key role in the quality control measures, including the localization of the carbon-reinforcement and the assessment of porosity within the concrete structure. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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15 pages, 7690 KiB  
Article
The Cracking and Tensile-Load-Bearing Behaviour of Concrete Reinforced with Sanded Carbon Grids
by Michael Frenzel, Enrico Baumgärtel, Steffen Marx and Manfred Curbach
Buildings 2023, 13(10), 2652; https://doi.org/10.3390/buildings13102652 - 21 Oct 2023
Cited by 1 | Viewed by 776
Abstract
This article presents the cracking and load-bearing behaviour of carbon-reinforced prismatic concrete tensile specimens. Grids with different geometries and impregnations were used as carbon reinforcement. In addition, the roving surfaces were partially coated with a fine sand to improve the bond between concrete [...] Read more.
This article presents the cracking and load-bearing behaviour of carbon-reinforced prismatic concrete tensile specimens. Grids with different geometries and impregnations were used as carbon reinforcement. In addition, the roving surfaces were partially coated with a fine sand to improve the bond between concrete and reinforcement. The article shows the influence of the different parameters on the developing cracks with respect to their width and spacing from each other. The material properties and tensile strengths of carbon concrete are also presented. These can be used for calculations. A fine-grained, commercially available shotcrete was used for the investigations. Based on the tests and results described in this article, an influence of the sanded carbon grids on the crack properties (crack widths, crack spacing) could be shown in comparison to unsanded carbon grids. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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26 pages, 13380 KiB  
Article
Vacuum-Assisted Die Casting Method for the Production of Filigree Textile-Reinforced Concrete Structures
by Iurii Vakaliuk, Silke Scheerer and Manfred Curbach
Buildings 2023, 13(10), 2641; https://doi.org/10.3390/buildings13102641 - 19 Oct 2023
Cited by 1 | Viewed by 876
Abstract
Concrete is the most widely used building material today. The enormous amount used goes hand in hand with high material consumption and CO2 emissions. Thus, building with concrete must be improved, becoming part of the solution on the way to climate-friendly building. [...] Read more.
Concrete is the most widely used building material today. The enormous amount used goes hand in hand with high material consumption and CO2 emissions. Thus, building with concrete must be improved, becoming part of the solution on the way to climate-friendly building. Non-metallic fibres are an alternative to corrosion-sensitive steel reinforcement, and they enable the production of filigree, high-performance, structured components with low concrete cover. This article presents an alternative manufacturing method. Our thesis was that concreting under negative air pressure conditions (APC) allows the easy production of complicated, thin-walled geometries without defects or loss of mechanical properties. We firstly present the principle of the vacuum-assisted method and its technical realization. The proof of concept included the production and laboratory tests of different specimens, casted under normal and negative APC. The fine concrete’s properties were determined in flexural and compression tests. Textile-reinforced concrete was analysed in tensile and bond tests as well as in bending trials on 2.7 m long shell elements. To summarize, it can be stated that the mechanical properties achieved were comparable, independent of the manufacturing conditions. The production quality of the shell elements was improved by concreting under negative APC. Finally, an outlook is given to further improve the method. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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19 pages, 3989 KiB  
Article
Systematic Mix Design Study on Geopolymers—Prediction of Compressive Strength
by Henning Kruppa and Anya Vollpracht
Buildings 2023, 13(10), 2617; https://doi.org/10.3390/buildings13102617 - 17 Oct 2023
Cited by 1 | Viewed by 1910
Abstract
Due to the demand for decarbonization of the construction sector, research on alkali-activated binders and material-minimized carbon-reinforced structures has gained momentum in recent years. Most of the research into alkali-activated binders is focused on developing market-ready alternatives, mainly using a trial-and-error approach. In [...] Read more.
Due to the demand for decarbonization of the construction sector, research on alkali-activated binders and material-minimized carbon-reinforced structures has gained momentum in recent years. Most of the research into alkali-activated binders is focused on developing market-ready alternatives, mainly using a trial-and-error approach. In this study, an attempt is made to identify and quantify the factors influencing compressive strength development. Due to their worldwide availability, investigations are being carried out into binders based on calcined clays and natural pozzolans. The goal is to develop a method to produce tailor-made AAB for continuous manufacturing methods to combine carbon reinforcement and alkali-activated materials. For this purpose, an experimental matrix with 20 variation parameters was set up, in which the activator solution and the precursor composition varied. The design of the experiments was used to minimize the number of experiments. It was shown that no single factor is responsible for the development of compressive strength but instead involves several interacting factors. It was possible to find empirical formulas for predicting the compressive strength after 2, 7, and 28 days. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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20 pages, 15369 KiB  
Article
Investigation of the Crack Behavior of CRC Using 4D Computed Tomography, Photogrammetry, and Fiber Optic Sensing
by Josiane Giese, Max Herbers, Frank Liebold, Franz Wagner, Szymon Grzesiak, Christoph de Sousa, Matthias Pahn, Hans-Gerd Maas, Steffen Marx, Manfred Curbach and Birgit Beckmann
Buildings 2023, 13(10), 2595; https://doi.org/10.3390/buildings13102595 - 14 Oct 2023
Cited by 1 | Viewed by 1220
Abstract
The highly irregular crack pattern of reinforced concrete has been studied primarily at the surface. The ability to extend image correlation into the interior of structures by using X-ray computed tomography (CT) opens up new possibilities for analyzing the internal mechanics of concrete. [...] Read more.
The highly irregular crack pattern of reinforced concrete has been studied primarily at the surface. The ability to extend image correlation into the interior of structures by using X-ray computed tomography (CT) opens up new possibilities for analyzing the internal mechanics of concrete. In order to enable a complete material characterization, it is necessary to study the crack geometry at the micro level in 3D images over time, i.e., 4D data. This paper presents the results of in situ CT tests that were carried out on carbon-reinforced concrete (CRC) beams subjected to bending load. The main objective of the tests was the experimental analysis of the evolution of individual cracks at different stages of their formation by applying digital volume correlation (DVC) to the 4D image data from the computed tomography. The results obtained from the CT were compared with other measurement techniques, such as distributed fiber optic sensing, clip gauges, and digital image correlation (DIC). Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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18 pages, 35661 KiB  
Article
Modular Construction of Topological Interlocking Blocks—An Algebraic Approach for Resource-Efficient Carbon-Reinforced Concrete Structures
by Sascha Stüttgen, Reymond Akpanya, Birgit Beckmann, Rostislav Chudoba, Daniel Robertz and Alice C. Niemeyer
Buildings 2023, 13(10), 2565; https://doi.org/10.3390/buildings13102565 - 10 Oct 2023
Viewed by 1280
Abstract
An algebraic approach to the design of resource-efficient carbon-reinforced concrete structures is presented. Interdisciplinary research in the fields of mathematics and algebra on the one hand and civil engineering and concrete structures on the other can lead to fruitful interactions and can contribute [...] Read more.
An algebraic approach to the design of resource-efficient carbon-reinforced concrete structures is presented. Interdisciplinary research in the fields of mathematics and algebra on the one hand and civil engineering and concrete structures on the other can lead to fruitful interactions and can contribute to the development of resource-efficient and sustainable concrete structures. Textile-reinforced concrete (TRC) using non-crimp fabric carbon reinforcement enables very thin and lightweight constructions and thus requires new construction strategies and new manufacturing methods. Algebraic methods applied to topological interlocking contribute to modular, reusable, and hence resource-efficient TRC structures. A modular approach to construct new interlocking blocks by combining different Platonic and Archimedean solids is presented. In particular, the design of blocks that can be decomposed into various n-prisms is the focus of this paper. It is demonstrated that the resulting blocks are highly versatile and offer numerous possibilities for the creation of interlocking assemblies, and a rigorous proof of the interlocking property is outlined. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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18 pages, 7203 KiB  
Article
Experimental Investigation of Beams Reinforced with Carbon 2D-Netzgitterträger Reinforcement
by Nazaib Ur Rehman, Marina Stümpel, Harald Michler, Paul Penzel, Birgit Beckmann, Lars Hahn, Chokri Cherif and Steffen Marx
Buildings 2023, 13(10), 2552; https://doi.org/10.3390/buildings13102552 - 9 Oct 2023
Cited by 1 | Viewed by 777
Abstract
The increasing popularity of carbon-reinforced concrete (CRC) is attributed to its exceptional tensile properties, low density, no corrosion phenomenon, and remarkable flexibility, allowing it to be easily shaped into various forms. However, there is a pressing need to explore this innovative and sustainable [...] Read more.
The increasing popularity of carbon-reinforced concrete (CRC) is attributed to its exceptional tensile properties, low density, no corrosion phenomenon, and remarkable flexibility, allowing it to be easily shaped into various forms. However, there is a pressing need to explore this innovative and sustainable alternative to traditional steel reinforcement. This motivates research and investigation of the feasibility of using a special 2D Netzgitterträger (NetzGT) reinforcement system, featuring a net-shaped fabricated textile made of multiple diagonally offset rovings with overlapping edge strands, as a viable alternative to traditional steel reinforcement in concrete beams. This 2D NetzGT reinforcement system has also been transformed into a 3D configuration for the development of a hollow core slab system. It is manufactured from carbon rovings with three different diagonal angles of 50°, 60°, and 70°. Laboratory experiments were conducted to assess the mechanical behavior of beams reinforced with the 2D NetzGT reinforcement. Tensile tests on strands were also performed with an increasing number of overlapped rovings to analyze their tensile strength. Additionally, single yarn pull-out tests were also conducted to examine the influence of the roving angle on the bond strength between the carbon textile roving and the concrete matrix. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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20 pages, 24934 KiB  
Article
Effect of Load Eccentricity on CRC Structures with Different Slenderness Ratios Subjected to Axial Compression
by Josiane Giese, Birgit Beckmann, Frank Schladitz, Steffen Marx and Manfred Curbach
Buildings 2023, 13(10), 2489; https://doi.org/10.3390/buildings13102489 - 30 Sep 2023
Cited by 1 | Viewed by 751
Abstract
The use of nonmetallic reinforcement in concrete aims at the decrease in material consumption by reducing the component sizes when compared to conventional reinforced concrete structures, which inherently results in very filigree structures. Although intensive basic research has been carried out on textile-reinforced [...] Read more.
The use of nonmetallic reinforcement in concrete aims at the decrease in material consumption by reducing the component sizes when compared to conventional reinforced concrete structures, which inherently results in very filigree structures. Although intensive basic research has been carried out on textile-reinforced concrete for about 30 years, the subject of stability behavior has hardly been investigated so far. This study focuses the fundamental understanding of the structural behavior of slender carbon-reinforced concrete (CRC) structures subjected to axial compression. Therefore, buckling experiments have been carried out in order to quantify the influence of two parameters: the slenderness ratio of the specimens (varying between 60 and 130) and the load eccentricity (0, 2, and 4 mm). The results of the specimens that were tested with the initial load eccentricities revealed a good overall agreement with those obtained by a second-order theory approach throughout all of the investigated slenderness ratios. For the centrally pressed samples that featured high slenderness ratios, the failure stresses could successfully be predicted with Euler’s buckling formula, whereas this theory overestimated the results of the specimens with intermediate to low slenderness ratios due to the plastic buckling phenomenon. The presented study emphasizes that the consideration of the stability problem is inevitable when designing material-efficient structures made of textile-reinforced concrete. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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28 pages, 30463 KiB  
Article
Analysis of Thin Carbon Reinforced Concrete Structures through Microtomography and Machine Learning
by Franz Wagner, Leonie Mester, Sven Klinkel and Hans-Gerd Maas
Buildings 2023, 13(9), 2399; https://doi.org/10.3390/buildings13092399 - 21 Sep 2023
Cited by 1 | Viewed by 1246
Abstract
This study focuses on the development of novel evaluation methods for the analysis of thin carbon reinforced concrete (CRC) structures. CRC allows for the exploration of slender components and innovative construction techniques due to its high tensile strength. In this contribution, the authors [...] Read more.
This study focuses on the development of novel evaluation methods for the analysis of thin carbon reinforced concrete (CRC) structures. CRC allows for the exploration of slender components and innovative construction techniques due to its high tensile strength. In this contribution, the authors have extended the analysis of CRC shells from existing research. The internal structure of CRC specimens was explored using microtomography. The rovings within the samples were segmented from the three-dimensional tomographic reconstructions using a 3D convolutional neural network with enhanced 3D data augmentation strategies and further analyzed using image-based techniques. The main contribution is the evaluation of the manufacturing precision and the simulation of the structural behavior by measuring the carbon grid positions inside the concrete. From the segmentations, surface point clouds were generated and then integrated into a multiscale framework using a parameterized representative volume element that captures the characteristic properties of the textile reinforcement. The procedure is presented using an example covering all necessary design steps from computed tomography to multiscale analysis. The framework is able to effectively evaluate novel construction methods and analyze the linear-elastic behavior of CRC shells. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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21 pages, 20131 KiB  
Article
Embroidered Carbon Reinforcement for Concrete
by Julian Konzilia, Jonas Wachter, Matthias Egger, Christoph Waltl, Thomas Fröis, Thomas Bechtold and Jürgen Feix
Buildings 2023, 13(9), 2293; https://doi.org/10.3390/buildings13092293 - 8 Sep 2023
Viewed by 1174
Abstract
This research focuses on the manufacturing process and mechanical properties of textile reinforcements fabricated using embroidery technology. The study investigates both 2D and 3D reinforcement products and compares the advantages and possibilities of embroidery technology with other manufacturing methods. A series of tests [...] Read more.
This research focuses on the manufacturing process and mechanical properties of textile reinforcements fabricated using embroidery technology. The study investigates both 2D and 3D reinforcement products and compares the advantages and possibilities of embroidery technology with other manufacturing methods. A series of tests using carbon reinforcement is conducted, and the results are presented and evaluated comprehensively. The uniaxial tensile tests reveal the characteristic behavior of carbon-reinforced concrete (CRC). Furthermore, the bonding behavior between the concrete matrix and embroidered carbon reinforcement is analyzed utilizing asymmetric pull-out tests, demonstrating that the embroidered reinforcements provide a sufficient bond. In addition to conventional 2D reinforcements, 3D reinforcements were also investigated, which can be efficiently manufactured using the TFP (tailored fiber placement) technology. Through the implementation of stirrup rovings, shear failure loads can be increased significantly. The results suggest that the mechanical properties of the reinforcement are influenced by the manufacturing process, which is particularly evident in the variation between longitudinal and transverse directions. The research highlights the potential benefits of using embroidery technology for textile reinforcement and indicates areas for further research and optimization in the manufacturing process. A pilot project that utilizes the embroidered reinforcement is currently under construction. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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14 pages, 3990 KiB  
Article
An Approach to Predicting the Ballistic Limit of Thin Textile-Reinforced Concrete Plates Based on Experimental Results
by Marcus Hering, Jürgen Sievers, Manfred Curbach and Birgit Beckmann
Buildings 2023, 13(9), 2234; https://doi.org/10.3390/buildings13092234 - 2 Sep 2023
Cited by 2 | Viewed by 756
Abstract
In this article, a partial selection of experiments on enhancing the impact resistance of structural components with non-metallic, textile-reinforced concrete is discussed. The focus is on the experimental investigations in which the impact resistance of thin, textile-reinforced concrete plates is characterized. The article [...] Read more.
In this article, a partial selection of experiments on enhancing the impact resistance of structural components with non-metallic, textile-reinforced concrete is discussed. The focus is on the experimental investigations in which the impact resistance of thin, textile-reinforced concrete plates is characterized. The article discusses the materials, fabrics and test setup used. For the experimental work, a drop tower from the Otto Mohr Laboratory, which belongs to the Technische Universtät Dresden, was used. Furthermore, the experimental results are presented and evaluated using different methods. Based on the collected data, a suitable approach to determining the perforation velocity of an impactor through the investigated thin, textile-reinforced concrete plates is shown. Full article
(This article belongs to the Special Issue Research on the Performance of Non-metallic Reinforced Concrete)
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