Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (49) (entfernen)
Sprache
- Englisch (30)
- Deutsch (18)
- Mehrsprachig (1)
Schlagworte
- Rheology (8)
- Baustoffe (6)
- Concrete (6)
- AKR (4)
- Durability (4)
- Hochleistungsbeton (4)
- UHPC (4)
- Versuche (4)
- Acoustic emission (3)
- Degradation (3)
- Polycarboxylate ether (3)
- Rheologie (3)
- ASR (2)
- Alkali-Kieselsäure-Reaktion (2)
- Alkali-silica reaction (2)
- Automated expansion measurement (2)
- Beton (2)
- Betontechnologie (2)
- Cement paste (2)
- High performance concrete (2)
- Korrosion (2)
- Microstructure (2)
- Mineral additions (2)
- Nanotechnologie (2)
- Polymer cement concrete (PCC) (2)
- Polypropylene fibres (2)
- Portland cement (2)
- Repair mortar (2)
- Repair systems (2)
- Robustheit (2)
- Robustness (2)
- Selbstverdichtender Beton (2)
- Self-compacting concrete (2)
- Sprayed polymer cement concrete (SPCC) (2)
- Stabilising agent (2)
- Starch ether (2)
- Superplasticizer (2)
- Thermal treatment (2)
- Ultrasound (2)
- 60 °C-Betonversuch (1)
- ASR damage (1)
- ASR modelling (1)
- Accelerated concrete prism test (1)
- Accelerated testing (1)
- Acoustic emissions analysis (1)
- Admixtures (1)
- Alkali silica reaction (1)
- Alkali-silica-reaction (1)
- Alkali–silica reaction (1)
- Allgemeines (1)
- Anti-Graffiti (1)
- Anti-graffiti agent (1)
- Auslaugung (1)
- Autogenes Schwinden (1)
- Automatische Dehnungsmessung (1)
- BOFS (1)
- Baustellenanwendung (1)
- Baustoff (1)
- Behandlungsparameter (1)
- Betonfahrbahndecken (1)
- Betoninstandsetzung (1)
- Biofilm (1)
- Biopolymers (1)
- Bioreceptivity (1)
- Brandschutz (1)
- Brick (1)
- Building Materials (1)
- Building and Construction (1)
- Cement (1)
- Cementitious materials (1)
- Chloride attack (1)
- Cleaning efficacy (1)
- Climate simulation concrete prism test (1)
- Coarsely dispersed systems (1)
- Compatibility (1)
- Compressive strength (1)
- Computed tomography (1)
- Computertomographie (1)
- Concentration (1)
- Concrete (E) (1)
- Concrete Prism Test at 60 °C (1)
- Concrete pavement (1)
- Concrete pavements (1)
- Concrete rehabilitation (1)
- Concrete's porosity (1)
- Cultural Heritage (1)
- Cyclic loading (1)
- Cyclic traffic loading and mechanical pre-damage (1)
- Damage analysis (1)
- Degradation (C) (1)
- Desiccation (1)
- Developing building materials (1)
- Diutan gum (1)
- EDX (1)
- Early cement hydration (1)
- Elevated temperatures (1)
- Ettringit (1)
- External alkalis (1)
- Fahrbahn (1)
- Fahrbahndeckenbetone (1)
- Fast measurement (1)
- Fatigue loading (1)
- Festigkeit (1)
- Festigkeitssteigerung (1)
- Fire Spalling (1)
- Fließmittel (1)
- Flow of concrete (1)
- Flow of mortar (1)
- Flüssigkeitstransport (1)
- Forschung und Entwicklung (1)
- Fracture energy (1)
- Fresh concrete (A) (1)
- Frischbetoneigenschaften (1)
- Frühe Zementhydratation (1)
- General Materials Science (1)
- Graffiti (1)
- Green facades (1)
- HRWRA (1)
- Haltezeit (1)
- High resolution (1)
- High strength concrete (1)
- High temperatures (1)
- Holistic concept (1)
- Hydratation (1)
- Hydration products (1)
- Hydrogarnet (1)
- Hydrothermal treatment (1)
- Hydroxylellestadite (1)
- In-situ (1)
- Innovative Prüftechnik (1)
- Instandsetzungsmörtel (1)
- Instandsetzungssysteme (1)
- Ionentransport (1)
- Laser-induced breakdown spectroscopy (1)
- Leaching of alkalis (1)
- Limestone (1)
- Mechanische Vorschädigung (1)
- Messtechnik (1)
- Micro cracks (1)
- Micro-Crack (1)
- Microcracks (1)
- Microfiller (1)
- Mikrofiller (1)
- Mikromechanik (1)
- Mikrorissbildung (1)
- Mikrorisse (1)
- Mikrostruktur (1)
- Mischungsentwurf (1)
- Mitigation strategies (1)
- Mixture composition (1)
- Modeling (E) (1)
- Modellierung (1)
- Monitoring (1)
- Monitoring of damage (1)
- Nachbehandlung (1)
- Nachhaltigkeit (1)
- Naturstein (1)
- Non-destructive testing (1)
- On-Site Application III (1)
- PP-Fasern (1)
- Pavement concrete (1)
- Performance (1)
- Permeability (C) (1)
- Phase development (1)
- Polycarboxylate (1)
- Polycarboxylate ether vicat (1)
- Polycarboxylatether (1)
- Polymer-Zement Beton (PCC) (1)
- Polymer-Zement Spritzbeton (SPCC) (1)
- Polypropylen-Fasern (1)
- Polypropylene Fibres (1)
- Polypropylene fibers (1)
- Polysaccharides (1)
- Porenstruktur (1)
- Portland cement Initial hydration (1)
- Praxis (1)
- Prüfmethoden (1)
- Rasterelektronenmikroskopie (1)
- Rheology (A) (1)
- Risse (1)
- Road pavement (1)
- Sample holder (1)
- Scanning electron microscopy (1)
- Schadensanalyse (1)
- Schallemissionsanalyse (1)
- Schwinden (1)
- Schädigende AKR (1)
- Schädigungsprozesse (1)
- Secondary aggregates (1)
- Secondary materials (1)
- Self-Compacting Concrete (1)
- Self-consolidating concrete (1)
- Setting (1)
- Shrinkage (1)
- Silikastaub (1)
- Simulation (1)
- Spatial analyses (1)
- Sphingan (1)
- Stabilising agents (1)
- Stabilizer (1)
- Stahlfasern (1)
- Starch (1)
- Stofftransport (1)
- Stone (1)
- Straßenbeton (1)
- Structural fire protection (1)
- Sulfate attack (C) (1)
- Sulphate attack (1)
- Sulphate-chloride attack (1)
- Superplasticizers (1)
- Surface interactions (1)
- Sustainability (1)
- Sustainable evaluation (1)
- Synchrotron (1)
- Temperatur (1)
- Temperature (1)
- Tensile strength (1)
- Thermal analysis (1)
- Thermal strain (1)
- Tobermorite (1)
- Transient strain (1)
- Transport process (1)
- Transportprozesse (1)
- Ultra-Hochleistungsbeton (1)
- Ultrahigh-performance concrete (UHPC) (1)
- Ultrahochleistungsbeton (1)
- Ultrasonic velocity (1)
- Verkehr (1)
- Vicat (1)
- Viscosity modifying agents (1)
- Vorlagerungszeit (1)
- Vorschädigung (1)
- Wärmebehandlung (1)
- X-Ray diffraction (1)
- X-ray diffraction (1)
- X-ray diffraction (B) (1)
- X-ray diffraction (XRD) (1)
- XRD (1)
- Yield stress (1)
- Zerstörungsarme und zerstörungsfreie Prüfverfahren (1)
- Zonation (1)
- Zonierung (1)
- Zyklische Belastung (1)
- Zyklischen Belastung (1)
- end-of-life phase (1)
- masonry (1)
- sustainability (1)
- zyklische Belastung (1)
- Äußere Alkalizufuhr (1)
Organisationseinheit der BAM
Paper des Monats
- ja (1)
Der Einfluß der Mischungszusammensetzungen auf das frühe autogene Schwinden der Bindemittelmatrix von Hochleistungsbetonen wurde durch Korrelation mit der Hydratationskinetik untersucht. Durch die Analyse der Verformungsgeschwindigkeiten konnte eine Unterscheidung zwischen plastischen und spannungsinduzierenden Verformungen vorgenommen werden.
This paper presents the results of an
experimental study on the transient strain of high
strength concrete (HSC) under heating up to 750 °C
and the impact of polypropylene (PP) fibers. Concerning
this topic only few results are available in the
literature and systematic investigations are missing.
However, basic knowledge is necessary for the
understanding of the internal damage processes in
the material as well as for heated structures. The
transient strain during heating can be separated in two
basic components: the free thermal strain and the
mechanical strain. They were experimentally determined
exemplarily for one HSC. For the determination
of the mechanisms of transient strain and particularly
the influence of PP fibers different techniques were
applied. In this context the monitoring of the microcracking
was done for the first time with acoustic
emission analysis in combination with ultrasonic
measurements. This new approach helps fundamentally
to explain the impact of PP fibers on free thermal
strain and mechanical strain during heating up.
Furthermore weight loss measurements were carried
out to characterize the moisture transport. It was
shown that the PP fibers cause an acceleration of the
moisture transport in the temperature range from 200
to 250 °C which leads to drying shrinkage in opposite
direction to the free thermal strain. Hence this paper is
a contribution to the general understanding of the
impact of PP fibers in HSC at high temperatures and
emphasizes the important influence of PP fibers on the
thermal and mechanical induced strain of HSC.
Bauteile bzw. Tragwerke aus Hochleistungsbetonen müssen in der Regel gegen brandinduzierte Abplatzungen mit geeigneten Maßnahmen geschützt werden, um einen ausreichenden Feuerwiderstand im Brandfall zu gewährleisten. Die bisher wirtschaftlich und technologisch sinnvollste Methode zur Verhinderung von explosionsartigen Betonabplatzungen im Brandfall ist die Zugabe von Polypropylen-Fasern. Die Wirksamkeit der Fasern konnte zwar empirisch gezeigt werden, es stellt sich allerdings die Frage, welche Mechanismen zur Verhinderung der Abplatzungen führen. Der vorliegende Beitrag fasst bisherige Theorien zur Wirkungsweise von Polypropylen-Fasern in brandbeanspruchten Hochleistungsbetonen zusammen und stellt eine innovative Methodologie zur Erforschung der mikrostrukturellen Prozesse vor. Die Ergebnisse zeigen, dass die nach dem Schmelzen und Zersetzen der Polypropylen-Fasern frei werdenden Mikrokanäle durch eine gleichzeitig einsetzende Mikrorissbildung netzartig verbunden werden. Die Mikrorissbildung ermöglicht somit den Abbau von Eigen- und Zwangsspannungen im Beton (mechanischer Effekt) und die Entstehung eines Transportwegesystems für den ausströmenden Wasserdampf (Permeationseffekt).--------------------------------------------------------------------------- Structural members and bearing structures of high performance concrete generally have to be protected against explosive spalling due to fire exposure to guarantee a sufficient fire resistance. Up to now, the economically and technologically most worthwhile method to prevent explosive spalling is the addition of polypropylene fibres. Though the effectiveness of the fibres could be shown empirically, the mechanisms preventing explosive spalling are still debatable. The present article summarizes the existing theories concerning the mode of action of polypropylene fibres in fire exposed high performance concretes and presents an innovative methodology for analysing the micro structural processes. The results show that due to the thermal decomposition of the polypropylene fibres micro channels are created and simultaneously connected due to a netlike micro crack formation. This enables the relief of internal stresses (mechanical effect) and the formation of a permeable transport system for the escaping water vapour (permeation effect).
Self-compacting concrete (SCC) differs substantially from normal concrete as regards the quantity of superplasticiser dosage. The functionality of superplasticisers, based on the polycarboxylate ether (PCE) superplasticiser customary with SCC, is nowadays very well understood at construction material research level. However, knowledge concerning pertinent correlations does not always permeate practice to an equal extent. PCEs are extremely polymorphic as opposed to earlier superplasticiser groups, which still possess a considerable proportion of the superplasticiser market. The geometry of polymers can be adjusted individually to performance characteristics required for certain uses. Yet, in selecting a superplasticiser for its specified rheological properties, a very strong influence can equally be exerted simultaneously on the subsequent hydration process. The charge density of the PCE employed also plays a key role in connection with both rheology and early hydration.
Der Einsatz von Sekundärrohstoffen im Betonbau kann einen wesentlichen Beitrag zu einer nachhaltigen Ressourcenwirtschaft im Bauwesen leisten. Sekundärrohstoffe (Recycling-Baustoffe, RC-Baustoffe) finden bereits Anwendung als Roh- bzw. Brennstoffe in der Portlandzementklinkerherstellung, als Zementbestandteile, als Betonzusatzstoffe sowie als sekundäre Gesteinskörnungen in Beton. In einem Teilprojekt des DAfStb/BMBF-Verbundforschungsvorhabens 'Nachhaltig Bauen mit Beton' wurde das Einsatzpotenzial von Sekundärrohstoffen in Beton untersucht. Hierbei spielen sowohl technische als auch ökologische und ökonomische Fragestellungen eine wichtige Rolle. Vor diesem Hintergrund wurde eine Bewertungsgrundlage mit ganzheitlicher Betrachtung von Nachhaltigkeitsaspekten (Technik, Ökologie, Ökonomie) ausgearbeitet. Dieses Bewertungskonzept umfasst die vier Bewertungsschritte: I. Grundsätzliche Überlegungen, II. Vorteile für das nachhaltige Bauen, III. Alternative Bewertungswege und IV. Sensitivitätsanalysen. Das Bewertungskonzept wurde am Beispiel der bereits im Betonbau eingesetzten rezyklierten Gesteinskörnungen entwickelt.----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Nowadays there are several applications of secondary mineral materials and residues. In the framework of the German research project 'Sustainable Building with Concrete', a concept to assess the applicability of already used and new secondary materials in concrete has been developed. It considers sustainability aspects and includes the following four assessment steps: I. Basic considerations, II. Advantages for sustainable construction, III. Alternative paths of application, and IV. Sensitivity analysis. Depending on changing technical, ecological and economic aspects, the assessment has to be performed for changed technical, ecological and economic conditions as necessity arises.
Cultural Heritage objects are in many cases invaluable and irrecoverable, therefore their protection is a prior goal. One threat arises by intentionally defacing such objects with graffiti. One possibility to face the imminent threat is the application of a surface protection in form of anti-graffiti systems (AGS). However, the knowledge about the performance and durability of AGS on substrates used for historical buildings is still fragmented. The goal of the presented study was to investigate the performance of a newly developed agent in comparison to a selection of commercial anti-graffiti agents on different substrates, which were used for historical buildings. Four commercial anti-graffiti agents with different chemical formulations were selected and tested with the new agent on different stone and brick substrates. The results showed clearly that AGS based on dense, water vapour impermeable coatings are not suitable to porous substrates such as sandstone, brick or porous limestone due to their impair of the hygric properties and the visual appearance of a substrate. The new agent could not completely reach the cleaning efficacy of the dense coatings but exhibited a much lower impact on the properties of the substrate and was therefore better compatible to historical surfaces.
Trotz der zahlreichen Möglichkeiten zur Beeinflussung der Mörteleigenschaften durch Mischungsmodifikationen ist es nahezu unmöglich, einzelne Eigenschaften unabhängig von anderen zu verändern. Bei einer Mischungsoptimierung muss im Einzelfall immer entschieden werden, welcher der gewünschten Eigenschaften die höchste Priorität zukommt. Anhand von Parameterstudien wird im vorliegenden Artikel verdeutlicht, wie es für bestimmte Anwendungen sinnvoll sein kann, die Verschlechterung einzelner Eigenschaften zu akzeptieren, wenn dadurch eine für den speziellen Einsatzfall essenzielle Eigenschaft verbessert werden kann. Die komplexen Wechselwirkungen der einzelnen Bestandteile fuhren dazu, dass auch scheinbar widersprüchliche Kombinationen von Zusatzmitteln im Einzelfall erforderlich werden können. Zur Anpassung der meisten Mörteleigenschaften gibt es verschiedene Möglichkeiten der Zielerreichung mit jeweils unterschiedlichen Nebeneffekten. Frisch- und Festmörteleigenschaften sind dabei gleichermaßen zu beachten.
Wärmebehandlung und Autoklavierung von UHPC - Neue Perspektiven für die Betonfertigteilindustrie
(2011)
Das Gefüge von UHPC ist durch eine dicht gepackte und fehlstellenarme Matrix gekennzeichnet. Eine zusätzliche Optimierung ist durch eine Wärmebehandlung bzw. hydrothermale Nachbehandlung (Autoklavierung) unter einem Wasserdampfsättigungsdruck möglich. Die Wärmebehandlung von Beton ist ein in der Betonfertigteilindustrie geläufiges Verfahren, um die Erstarrungszeit zu verkürzen und höhere Frühfestigkeiten zu erreichen.
This paper presents the results of an experimental study on the influence of polypropylene (PP) fibres on the thermal strain of high strength concrete (HSC) at temperatures up to 750°C. Concerning this topic only few results can be found in the literature and systematic investigations are missing. However, basic knowledge is necessary to understand the internal damage processes as well as for structural design.
To explain the differences in the thermal strain of HSC with and without addition of PP fibres the internal damage processes were investigated with acoustic emission (AE) analysis and ultrasound (US). Furthermore the weight loss was measured continuously during heating to monitor the drying of the specimen. This novel approach by combining these different methods with strain measurements at high temperatures allows the integral description of the internal damage processes. The results reveal significant differences in the thermal strain of HSC when PP fibres are added. Between 200°C and 250°C the thermal strain of HSC with PP fibres is superimposed by shrinkage caused by accelerated drying. Above 250°C it is lower than that of plain HSC without PP fibres. It is supposed that it is caused by a more homogeneous distribution of micro cracks whereby the fibre beds acting as defects in the concrete.
Hence this paper gives a contribution to the general understanding of the impact of PP fibres in HSC at high temperatures and points out the influence of the fibres on the thermal strain of HSC.