Kurzfassung
Aufgrund einer verschärften Einstufung von Titandioxidpulvern als vermutlich krebserregender Gefahrenstoff, ist mit einer eingeschränkten Nutzbarkeit des fotokatalytisch aktiven Stoffes ...in allen Sektoren zu rechnen. In dieser Arbeit wird daher eine alternative Anwendung von Titandioxid als fotokatalytisch aktive Bauteilbeschichtung in der Form von angeordneten Nanoröhren vorgestellt, da diese aufgrund ihrer Geometrie nicht von der Neuregulierung betroffen sind. Dies wird durch den direkten Transfer einer durch Anodisation hergestellten Nanoröhrenstruktur auf das zementbasierte Bauteil bewerkstelligt. Die fotokatalytischen Eigenschaften bleiben dabei erhalten.
Im Rahmen dieser Arbeit werden dazu Titandioxid‐ und dotierte Titandioxidnanoröhren, welche aus einer Titan‐Eisen‐Legierung synthetisiert wurden untersucht. Zunächst werden sowohl der Herstellungsprozess der Nanoröhren als auch deren Nachbehandlung, um einen Transfer auf den Baustoff zu bewerkstelligen, beschrieben. Anschließend wird gezeigt, dass ein Transfer der Nanoröhren auf den Baustoff in der Fertigteilbauweise erfolgen kann. Die Charakterisierung des Verbundwerkstoffes erfolgt anschließend anhand morphologischer und kristallographischer Daten. Die fotokatalytische Aktivität der Nanoröhren wird mittels eines Farbstoff‐Degradations‐Versuches untersucht.
Kurzfassung
Die Carbonatisierung von Beton kann einerseits zu Schäden bei Stahlbetonbauwerken führen, andererseits kann der Beton so CO2 speichern und damit seinen CO2‐Fußabdruck verringern. In ...diesem Beitrag wird dargestellt, wie eine effiziente Beschleunigung der Carbonatisierung durch Anlegen eines geringen äußeren Drucks erreicht werden kann. Damit wird neben der Diffusion der wesentlich schneller ablaufende Transportmechanismus der Permeation ausgenutzt, der das CO2 tiefer in das Probeninnere transportiert und damit in kurzer Zeit die Bestimmung des Carbonatisierungswiderstand zementgebundener Materialien ermöglicht. Hierzu wurde eine Prüfeinrichtung entwickelt, die es ermöglicht, die CO2‐Konzentration und in gewissen Grenzen auch relative Luftfeuchte sowie die Temperatur gezielt einzustellen und zu steuern, um so Mörtel‐ und Betonproben schnell und präzise zu carbonatisieren. Der Einfluss verschiedener Druckstufen und Wechselzyklen wird dargelegt und die resultierenden chemischen und physikalischen Veränderungen der Proben bestimmt. Als besonders effizient und gleichzeitig realitätsnah erwies sich die konstante CO2‐Beaufschlagung mit 3 Vol.‐% CO2 mit zusätzlichem, moderatem Gasdruck. Das hier entwickelte Verfahren kann daher genutzt werden, um Betone schnell und effizient in zeitraffenden Materialtests hinsichtlich Carbonatisierungswiderstand zu charakterisieren.
•The production of green sustainable concrete utilising ultrafine palm oil fuel ash (UPOFA) and waste plastic Polyethylene Terephthalate (PET) fibres was presented in this study.•The proportions of ...UPOFA were (20% and 40%) as a partial replacement of the total cement binder combined with 1% PET fibres.•The combination of UPOFA and PET fibres enhanced strength and transport properties of Ultra-High-Performance PET Green Concrete (UHPPGC).
The production of green sustainable concrete with enhanced performance against severe environmental conditions by using recycle waste materials has been a primary concern for recent studies. This article reports a study on investigating the effect of incorporating ultra-fine palm oil fuel ash (UPOFA) with shredded recycled waste bottle in form of Polyethylene Terephthalate (PET) on the engineering and transport properties of ultra-high-performance concrete. UPOFA was used as a partial replacement binder in varied proportions (20% and 40%) of the total cement binder, whereas shredded recycled PET bottles were added as reinforced fibre by 1% of the total mix volume. The greatest compressive strength was registered by a combination of 20% UPOFA and PET fibre in U20-UHPPGC. The combination of 40% UPOFA and PET fibres in U40-UHPPGC mix demonstrated a superior enhancement in terms of transport properties at the age of 28 days, such as porosity, initial surface absorption, gas permeability, water permeability and rapid chloride permeability. Thus, pozzolanic UPOFA can improve the engineering and transport properties of ultra-high-strength concrete. The overall results indicated that the PET fibre reinforced with UPOFA can produce UHPPGC with promising improvements in engineering and transport properties. The incorporation of waste materials into concrete constructions can reduce cement consumption and prevent the environmental pollution with save energy at the same time.
Reduction of CO
emissions associated with cement production is challenging in view of the increasing cement demand and the fact that major part of the emissions originates from the main raw material ...used - limestone - which can be only to extremely low amount substituted. A Carbon Capture and Utilization (CCU) approach based on mineralization of fines derived from concrete appears to be a viable alternative to reduce these emissions. The CO
sequestration and the reactivity of the obtained carbonated recycled fines is experimentally demonstrated for lab as well as industrial materials for different mineralization conditions. It is shown that all CO
originally released by limestone calcination during clinker production can be sequestered by the full carbonation of the fines within a short time. Upon full carbonation, gels with pozzolanic properties form in the fines irrespective of the conditions tested. The carbonated fines have specific CO
savings more than 30% higher than the simple clinker replacement by limestone.
Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D ...printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.
The fabrication of novel reinforced concrete structures using digital technologies necessarily requires the definition of suitable strategies for reinforcement implementation. The successful ...integration of existing reinforcement systems, such as steel rebar, rods, wires, fibres or filaments, will indeed allow for printed concrete structures to be designed using standard structural codes. However, reinforcement integration has to be compatible with either the specific printing technique adopted for the structural element production or with its shape. This paper provides a systematic overview of a number of digital fabrication techniques using reinforced concrete that have been developed so far, proposing a possible organization by structural principle, or place in the manufacturing process.
•SLFSCRC mixtures with different CR and binder content were investigated.•Increasing CR content negatively affected the mechanical properties of mixtures.•Performance of SLF compared to other SCMs ...was investigated.•Adding MK and SFs to SLFSCRC mixtures improved mechanical properties of mixtures.•Mixtures with maximized percentage of CR and SFs further enhanced the STS and FS.
This investigation was carried out to evaluate the effect of using silica fume on the development and optimization of self-consolidating rubberized concrete (SCRC). In particular, the investigation aimed to optimize successful silica fume self-consolidating rubberized concrete (SLFSCRC) mixtures with maximized percentage of crumb rubber (CR) (as a partial replacement of fine aggregate) and minimized strength reduction. The study also compared the behaviour of silica fume (SLF) with other supplementary cementitious materials (SCMs) in optimized SCRC mixtures. The results indicated that the use of SLF helped to develop SCRC mixtures with improved strength and acceptable fresh properties with up to 25% CR. Using SLF or metakaolin (MK) in SCRC exhibited superior behaviour among other SCMs in terms of strength. However, using SLF in SCRC showed better mixture flowability and less dosage of high range of water reducer admixture compared to using MK in SCRC. It was also noticed that adding steel fibres (SFs) to SLFSCRC mixtures greatly enhanced the mechanical properties, especially the splitting tensile strength and flexural strength. The results also showed that since there is no challenge to achieving acceptable self-compactibility (especially passing ability) in vibrated rubberized concrete, it was possible to develop silica fume vibrated rubberized concrete (SLFVRC) with higher percentages of CR and SFs and with further improved flexural and tensile strengths.
This book provides an updated state-of-the-art review on new developments in alkali-activation. The main binder of concrete, Portland cement, represents almost 80% of the total CO2 emissions of ...concrete which are about 6 to 7% of the Planet's total CO2 emissions. This is particularly serious in the current context of climate change and it could get even worse because the demand for Portland cement is expected to increase by almost 200% by 2050 from 2010 levels, reaching 6000 million tons/year. Alkali-activated binders represent an alternative to Portland cement having higher durability and a lower CO2 footprint. * Reviews the chemistry, mix design, manufacture and properties of alkali-activated cement-based concrete binders * Considers performance in adverse environmental conditions. * Offers equal emphasis on the science behind the technology and its use in civil engineering.
Abstract
Neue Materialien ermöglichen neue Bauformen und Konstruktionsarten. Erste Bauprojekte mit den neuen Materialien zeigten aber, dass zunächst weiterhin nach traditionellen – im Falle von ...Carbonbeton dem Stahlbeton entlehnten – Konstruktionsprinzipien gebaut wird, herkömmliche Materialien also lediglich substituiert werden. Erst in Verbindung mit intelligenten Konstruktionsstrategien wird das volle Potenzial innovativer Werkstoffe ausgenutzt. Losgelöst von etablierten Denkmustern sollen im Sonderforschungsbereich/Transregio (SFB/TRR) 280 „Konstruktionsstrategien für materialminimierte Carbonbetonstrukturen – Grundlagen für eine neue Art zu bauen“ an der Technischen Universität Dresden und der RWTH Aachen University die Grundlagen für eine neue Form des Bauens mit Beton auf Basis tiefgreifender Erkenntnisse zum strukturmechanischen Verhalten neuartiger, mineralisch basierter Komposite geschaffen werden. Die neuen Leichtbau‐Konstruktionsstrategien und Werkstoffkombinationen reduzieren Ressourcen‐ und Energieverbrauch bei gleichzeitig hoher Gebrauchstauglichkeit, Tragsicherheit und Dauerhaftigkeit; eine anspruchsvolle Ästhetik leistet einen Beitrag zur Baukultur. Der langjährige Forschungsverbund von TU Dresden und RWTH Aachen vereint exzellente Kompetenzen, was die Erforschung des materialminimierten Bauens mit mineralischen Kompositen beflügeln wird. Im Beitrag werden die für den Zeitraum Juli 2020 bis Juni 2024 geplanten Forschungsaktivitäten vorgestellt.
Abstract
Collaborative research on carbon reinforced concrete structures in the CRC/TRR 280
New materials afford new building designs and construction types. Yet, first application projects using the new materials show that traditional construction principles are used, i. e. that conventional materials are merely substituted. Only combined with intelligent construction strategies it is possible to exploit the full potential of the innovative material carbon reinforced concrete. Detached from today's established thought patterns, the fundamentals for a new way of building with concrete shall be created in the frame of the Collaborative Research Centre Transregio (CRC/TRR) 280 “Design Strategies for Material‐Minimised Carbon Reinforced Concrete Structures – Principles of a New Approach to Construction” at Technische Universität Dresden and RWTH Aachen University, based on profound insights into the mechanical behaviour of novel mineral structures. Innovative construction strategies and material composites reduce the resource and energy consumption by means of novel lightweight construction principles and offer a high serviceability, ultimate capacity and durability. Furthermore, they are reflected in ambitious aesthetics evolving to a novel “art of construction”. The long‐term research alliance of TUD and RWTH pools the existing excellent competences, which will inspire research into material‐minimised construction with mineral composites. The article highlights the research activities planned for the period July 2020 to June 2024.
•Performance of SCC made with different replacement levels of Recycled Concrete Aggregates (RCA) with the use of Non Destructive Testing (NDT) techniques has been studied.•Non-destructive tests such ...as Electrical Resistivity, UPV and Rebound Hammer were conducted on various SCC mixes made with different replacement levels of Coarse Recycled Concrete Aggregates (CrRCA) and Fine Recycled Concrete Aggregates (FnRCA).•It has been observed that the SCC mixes containing low and intermediate percentage of RCA (CrRCA and FnRCA) as replacement of NA do not have any adverse effect on the overall performance.
The paper presents the results of an investigation conducted to evaluate the performance of Self Compacting Concrete (SCC) made with different replacement levels of Recycled Concrete Aggregates (RCA) with the use of Non Destructive Testing (NDT) techniques. Non-destructive tests such as Electrical Resistivity, Ultrasonic Pulse Velocity (UPV) and Rebound Hammer were conducted on the various SCC mixes made with different replacement levels of Coarse Recycled Concrete Aggregates (CrRCA) and Fine Recycled Concrete Aggregates (FnRCA) at different periods of curing. Compressive strength tests on all the SCC mixes were also conducted for reference. The results show that increase in the content of RCA as replacement of Natural Aggregates (NA), decreases the electrical resistivity, UPV and rebound numbers for all SCC mixes. The linear regression coefficients depict excellent relationship between electrical resistivity, UPV and rebound numbers with compressive strength at all curing ages. It has been observed that the SCC mixes containing low and intermediate percentage of RCA as replacement of NA do not report any negative effect on the overall performance of SCC. Using waste materials (RCA) in new concrete certainly reduces its cost, encourages the concrete industry and correspondingly leads to the effective management of Construction & Demolition (C&D) wastes.
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