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Investigation on tension and bonding behaviour of basalt fibre reinforced polymers in concrete structures For retrofitting of RC structures, the concrete cover of the renewed reinforcement has to be sufficient to ensure the durability. Alternative reinforcement like rebars of basalt fibre reinforced polymers (BFRP) gives the possibility to minimize the concrete cover ensuring durable structures due to their resistance against carbonation and chlorides. In this paper investigations on load‐bearing behaviour of BFRP reinforced test specimens as an excerpt from a research project on basalt fibre reinforced concrete as repairing material with shotcrete and also basalt rebars as additional strengthening reinforcement for fair faced concrete facades are presented. The tested BFRP rebars show higher tension strength and lower Young's Modulus as comparable steel reinforcement bars. In centrical tension tests on the BFRP reinforced concrete specimen longitudinal cracking due to high tension in the contact zone and a higher number and also higher widths of crosswise cracking appear. The load bearing behaviour can be confirmed by numerical simulation. The results of the investigation with the incident light microscope on prepared specimen after tension tests show an enhanced number of microcracks in the contact zone between BFRP rebar and cement matrix. In pull out tests always the concrete failed, never the BFRP rebars. The results of this investigation confirm the possibility to ensure durable concrete structures using BFRP reinforcement. Further tests have been carried out on the flexural strength behaviour, the fatigue strength and durability. At the moment BFRP rebars of various designs are tested. [ABSTRACT FROM AUTHOR]

Germany's first application of UHPFRC in railway bridge construction Part 2: Accompanying scientific investigations and measurement supervision of manufacture and in operation Ultra‐high performance fibre‐reinforced concrete (UHPFRC) is characterized by an extremely dense microstructure and thus very high strengths as well as excellent durability properties. This enables a material‐saving and weight‐reduced, slim construction method that opens up completely new possibilities and areas of application in precast bridge construction. In the course of the superstructure renewal of an existing railway bridge the material could now be used for the first time in Germany for a railway bridge in a particularly practical and advantageous way. The superstructure was designed as a trough‐shaped precast slab bridge in prestressed concrete construction with a very low construction height. This part 2 of the article deals on the one hand with accompanying experimental investigations on crack formation and on the flexural behavior of a purely steel fibre reinforced mock‐up of the bridge superstructure. On the other hand, the technical paper deals with the measurement supervision of manufacture and in operation. In addition to determining losses of prestress and hydration heat development, structural measurements were also carried out to determine the real structural responses in the course of test loads with defined axle loads. [ABSTRACT FROM AUTHOR]

Abstract: Influence of Thermal Treatment on the Strength of Fine‐Grained Ultra‐High Performance Concrete (UHPC/RPC) By means of targeted specific thermal post‐treatment, the bending tensile strength and compressive strength of Ultra‐High Performance Concrete (UHPC) can significantly be increased. In most publications, a pre‐storage time of 1–2 days, a holding temperature of 60–90 °C and a dwell time of 24–48 hours are recommended [1, 2]. Own preliminary investigations on the thermal treatment of fine‐grained UHPC (RPC) at the Institute for Structural Concrete of the University Duisburg‐Essen showed that improved results could be achieved by other variations. Therefore, more detailed investigations were carried out on the pre‐storage time and the holding temperature of two different UHPC mixtures. Furthermore, the influence of protection of the samples against dehydration during the thermal treatment was investigated. The results of these studies are documented and evaluated in this publication. It was found that the treatment temperature has the greatest influence on the compressive strength. The protection of the samples was crucial for the flexural strength. It should also be noted that different thermal treatment regimes led to the best results for the various mixing compositions. [ABSTRACT FROM AUTHOR]

Abstract: Sealing of joints in concrete with waterstops – the new German Standard DIN 18197 – Waterstops correctly designed, dimensioned and used The DIN 18197 “Sealing of joints in concrete with waterstops”, provides a set of rules for both, the planer and the contractor. In addition to relevant details for the design and the professional handling of waterstops on the construction site, selection diagrams are included which, in a simple way, allows the planner to select waterstops in dependence of the loads. This article addresses to the essential rules concerning the joint waterproofing with waterstop and explains by means of several examples and the DIN 18197 selection diagrams, how the planner can specify a waterstop complying with the loads. It is explained in detail what to consider when dealing with waterstops on the construction site. [ABSTRACT FROM AUTHOR]

Abstract: Influence of lateral constraint on the loadbearing and deformation characteristics of hollow core slabs in fire Prestressed hollow core slabs (HC slabs) are used particularly as ceiling systems in building construction for economic reasons. In 2007, a fire incident in a car park in Rotterdam caused partial detachment of the bottom concrete layer [1]. This resulted in a Europe‐wide discussion on the fire safety assessment of this type of construction. By now, many expert opinions, literature analyses and recent research on the fire resistance of constructions of prestressed hollow core slabs exist [2]. In the investigations, the bearing behaviour of HC slabs with rigid support, in particular with regard to the lateral force bearing capacity, was investigated among other things. Until now in the testing and evaluation of prestressed hollow core slabs in fire the obstruction of thermal induced lateral expansion is hardly considered. In practice, in case of fire an obstruction of the lateral expansion of the HC slabs may occur, if there is a very stiff boundary around the fire‐exposed ceiling area, e.g. by staircase cores or surrounding ceiling areas without any fire exposure. To investigate this question, appropriate experimental and numerical investigations were carried out at BAM on ceilings made of prestressed concrete hollow core slabs with different lateral restraint [3]. This article describes in detail the fire tests carried out in real scale and the results obtained from these tests. The investigations carried out at BAM have shown that with an increase in the lateral constraint, the horizontal cracking in the webs of the HC slab increases and the longitudinal cracking decreases. Despite the distinctive horizontal crack formation, the fire tests did not show a detachment of the bottom concrete layer. Likewise, there was no negative influence of the horizontal cracks on the load‐bearing and deformation behaviour of the fire‐stressed ceiling construction. The results from the fire tests will be available for the validation of numerical models in the future. [ABSTRACT FROM AUTHOR]

Abstract: Double wall systems in pressing groundwaterplanning – regulations – waterproofing – construction – typical errors The use of double wall systems in a pressing groundwater requires a special care during design, execution and supervision. This article highlights fundamental background information, explains typical faults and gives advice for the avoidance of them. [ABSTRACT FROM AUTHOR]

Abstract: Subsequent installation of ”white tank“ waterproof concrete basements in existing buildings Cases of damp damage, which are due to changed groundwater conditions in combination with construction that is not suitable for the exposure, have increased in recent years all over Germany. The affected basements often not only have to be waterproofed but also structurally strengthened. In the following article, various methods are described to waterproof and simultaneously structurally strengthen the affected buildings, depending on the relevant local conditions, by installing a waterproof concrete basement designed to resist water under pressure. [ABSTRACT FROM AUTHOR]

Abstract: Planning and execution of joints and joint sealing and waterproofing solutions for watertight concrete structures Watertight concrete structures, so called ”White Tanks“ or ”White Boxes“, generally have to prevent water penetration into the structure, or to its contents; alternatively they are designed and built to prevent water leakage from the structure, or to do both. In many cases joints in structures of waterproof concrete turn out to be a weak point. For this reason in watertight concrete construction works, the design engineers and the contractor must pay special attention to the waterproofing solutions for all of the joints. Construction joints, movement or expansion joints, controlled crack induced joints and penetrations are sealed and made watertight. Therefore the responsible engineer needs to have a good knowledge of the different joint sealing and waterproofing solutions that can be used. This article goes into the details of the different joint sealing and waterproofing systems and the basic rules for sealing. [ABSTRACT FROM AUTHOR]

Abstract: Waterproof concrete constructions – recommendations for the cooperation of client, planner, special planner and contractor For a successful implementation of waterproof concrete constructions, a particularly high planning and execution quality is essential and the monitoring of the execution is required. The present paper provides advice and assistance to builders, designers and contractors for the design and execution of waterproof concrete constructions. [ABSTRACT FROM AUTHOR]

Abstract: Essential changes in the new DAfStb‐Guideline on watertight concrete structures 2017 he DAfStb‐Guideline on watertight concrete structures (WU‐Guideline) of 2003 has been reviewed and is finished as new issue in 2017. In this process the gathered experiences and new knowledge has been considered. Essential changes and additions in the WU‐Guideline are the required design steps, an informative annex for coordination of the responsibilty for design parts, the introduction of rules for watertight concrete roofs, the using conditions of the design principles, increased requirements for design principle (b) with self‐healing of cracks and also for watertight element walls and the improvement of the readability and understandability as well as refined obligations of documentation. The use of the WU‐Guideline for high‐grade used basements requires a rethinking by using the design principles from calculating to construction with lower imposed deformations. [ABSTRACT FROM AUTHOR]

Impact of a concrete coating on the reinforcement corrosion in cracked concrete Cracks in reinforced concrete structures exposed to chlorides can significantly impair the durability. Cracks are a fast pathway for chlorides and corrosion initiation of the reinforcement is more likely. Relevant standards [1, 2] require additional measures to prevent chloride ingress into structures exposed to chlorides such as parking decks. Additional design principles to ensure the durability of parking decks are given by the German Society for Concrete and Construction Technology (DBV) [3]. One principle consists of the application of a crack bridging concrete coating to prevent further chloride and moisture supply once early cracking is completed even though chlorides are already present in the crack. This recommendation is in line with the repair principle W-Cl according to RL SIB [4] and the procedure 8.3 DIN EN 1504-9 [5] respectively with the objective to increase the concrete resistivity. In an extensive experimental study it can be shown that concrete coating prevents corrosion and can even stop macro cell corrosion successfully in bending cracks with short-term chloride exposure. The repassivation is based on the increase of the anodic polarization resistance due to oxide layer formation and/or limited supply of chlorides. The concrete resistivity increases as well because of ongoing drying of the concrete but its effect on the macro-cell activity is negligible. It remains to be determined which amount of chlorides can be left in the concrete to exclude on-going reinforcement corrosion reliably. [ABSTRACT FROM AUTHOR]

During hardening of concrete temperature depending strains occur. In the same period the material properties young's modulus, compressive strength and tensile strength etc. develop. Because of the reason that resistances and stresses are developing dependent the ongoing hydration a time history calculation is one way to calculate the ability to crack in every single time step. In a research project about decreasing the cost of reinforced concrete protection measures against natural hazards in water engineering the influence of different cement types on the possibility to get cracks because of restraint is worked out. This paper gives a detailed description of the used ABAQUS Finite-Element-Model. Two aspects of the results of the calculations are pointed out: The influence of different cement types on the crack ability and the consequences of different age of the concrete when the formwork is removed. [ABSTRACT FROM AUTHOR]

Guideline for the assumption of the effective concrete tensile strength within the minimum reinforcement check due to early cracking according to Eurocode 2-2 (DIN EN 1992-2/NA) In December 2015, the A1-amendment [1] for the German National Annex [2] of DIN EN 1992-1-1 was published. The amendment affects among others the assumption of the effective concrete tensile strength within the minimum reinforcement check due to early cracking. The following contribution elucidates the background, why a respective A1-amendment for DIN EN 1992-2/NA has not been provided. Furthermore, the main differences between building- and bridge constructions are outlined in order to constitute the different approach. [ABSTRACT FROM AUTHOR]

Um das tatsächliche Verhalten von Stahlbetonbauteilen unter vorwiegender Zwangbeanspruchung experimentell zu untersuchen, wurde an der Technischen Universität Graz ein neuer Versuchsaufbau konzipiert. Im Vordergrund steht hierbei die zusammenhängende Betrachtung der Spannungsgeschichte und Rissbildung, beginnend mit der erhärtungsbedingten Zwangbeanspruchung (früher Zwang) und der anschließenden Überlagerung mit weiteren Zwangbeanspruchungen in der Nutzungsphase (später Zwang). Ziel der experimentellen Untersuchung war es, die verbleibenden Zwangspannungen nach Spannungsrelaxation und Rissbildung zu quantifizieren sowie die Rissbreitenentwicklung im Nutzungszeitraum zu beobachten. Für den frühen Zwang wurde hierbei besonderes Augenmerk auf den Einfluss der realistischen Behinderungssituation (in der Regel teilweiser Zwang) und der thermischen Randbedingungen (insbesondere Auswirkungen thermischer Nachbehandlungsmaßnahmen) gelegt. Im späten Zwang fällt vor allem der Berücksichtigung des Bauteilzustands (Einzelriss oder abgeschlossenes Rissbild) eine entscheidende Rolle zu. Mit den Versuchsergebnissen kann gezeigt werden, dass die Effektivität von thermischen Nachbehandlungsmaßnahmen zur Vermeidung von Trennrissen sehr begrenzt ist und eine getrennte Betrachtung von frühem und spätem Zwang nicht immer zu einer sicheren Bemessung führt. Restrained Concrete Members - New Findings from Systematic Investigations with Restraint Frames for Reinforced Concrete In order to investigate the real structural behaviour of reinforced concrete members mainly subjected to restraint a new experimental set-up was designed at the Graz University of Technology. In the focus of interest is the continuous investigation of the stress history and crack development starting with restraint due to hardening and the subsequent superposition with further deformation impacts during service life. The experimental investigation aims at quantifying the remaining restraint stresses after stress relaxation and crack formation as well as observing crack development during service life. In the hardening phase the influence of a realistic placement condition (normally partial restraint) and the thermal boundary conditions (especially thermal curing) was paid attention to. During service life the consideration of the member condition (single crack pattern or stabilized crack pattern) is highly significant. Based on the experimental results it can be concluded that thermal curing has only a limited influence on preventing through cracks and the separate consideration of early restraint and service life impacts does not always lead to design on the safe side. [ABSTRACT FROM AUTHOR]

Beton verhält sich unter dynamischer Belastung anders als unter statischer Belastung. Als wesentliche stoffliche Ursache hierfür werden üblicherweise innere Transporteffekte bei niedrigen Dehnraten bis ca. ϵ = 1/s angenommen. Bei höheren Dehnraten bis ca. ϵ = 300/s werden vermutlich Trägheitseffekte bei der Bildung von Rissen maßgebend. Die messtechnische Erfassung dieser Effekte und die klare Trennung von stofflichen und strukturellen Phänomenen sind Gegenstand aktueller Forschung. Eine Möglichkeit, das Verhalten von Beton bei höheren Belastungsgeschwindigkeiten zu untersuchen, bietet der Split‐Hopkinson‐Pressure‐Bar‐Versuch (SHPB‐Versuch). Nachfolgend werden Versuche für einen Normalbeton C35/45 mit Belastungen im quasi‐statischen Bereich bis hin zu Lasten, die Dehnraten von bis zu ϵ = 211/s erzeugen, vorgestellt, ausgewertet und durch Simulationen abgebildet. In der Simulation wird ein Materialmodell verwendet, das auf einem um eine nicht‐lokale Formulierung der Plastizität erweiterten Modell der Mikroebenen basiert. Zusätzlich wird die Massenträgheit der Struktur berücksichtigt. Es wird aufgezeigt, dass die experimentell ermittelte höhere Beanspruchbarkeit des Betons bei gesteigerten Dehnraten numerisch abgebildet werden kann. Dynamic properties of concrete in experiment and simulation Concrete subjected to dynamic loads behaves differently compared to static loading. As an explanation at low strain rates up to ϵ = /s, internal transport effects are assumed to be originated in the material. At higher strain rates up to ϵ = 300/s, inertial effects during the formation of cracks are postulated. The experimental identification of these phenomena and the definite separation of their substantial and structural sources are subject to current research. The split Hopkinson pressure bar experiment enables the investigation of the behaviour of concrete subjected to dynamic loading. In the following, experiments in the range of quasi‐static loading up to loads that induce strain rates until ϵ = 211/s on a standard concrete C35/45 grade are presented, evaluated and simulated. In the simulation, a material model is applied that bases on the micro‐plane model extended by a non‐local formulation of plasticity. Furthermore, structural inertia effects are taken into account. It is shown that the experimentally found increase in strength of the concrete at higher strain rates can be modelled by the simulation. [ABSTRACT FROM AUTHOR]

Im Dezember 2015 ist eine A1‐Änderung [1] zum deutschen Nationalen Anhang [2] des Teils 1‐1 von Eurocode 2 [3] veröffentlicht worden. Die Änderung betrifft die zwei Themen Dauerhaftigkeit von tausalzbeanspruchten Verkehrsflächen (insbesondere Parkdecks) und Ansatz der wirksamen Betonzugfestigkeit bei der Ermittlung der Mindestbewehrung zur Begrenzung der Rissbreite bei früher Rissbildung. Beiden Sachverhalten ist eine mehrjährige Diskussion in Fachkreisen vorausgegangen. Der Beitrag soll die Hintergründe der Änderungen und deren Folgen für die Praxis erläutern. Explanations of amendment of the German National Annex to Eurocode 2 An A1‐Amendment [1] of the German National Annex [2] of Eurocode 2, Part 1‐1 [3] has been published in December 2015. The amendment affects the two topics durability of traffic areas under chloride exposure (especially parking levels) and assumption of the effective concrete tensile strength at calculation of the minimum reinforcement for crack control due to early cracking. According these two topics a multiannual discussion in expert forums was foregone. This paper should explain the background of the changes and the consequences for the practice. [ABSTRACT FROM AUTHOR]

Innerhalb der beim DAfStb eingerichteten Ad‐hoc‐Gruppe “Dauerhaftigkeit von befahrenen Parkdecks” wurde vereinbart, eine Gesamtsystematik zu den Regelungen für die Dauerhaftigkeit von befahrenen Verkehrsflächen zu entwickeln, die aus einer Normenvorlage und aus Erläuterungen für das Heft 600 sowie Ausführungen für das DBV‐Merkblatt “Parkhäuser und Tiefgaragen” bestehen. Der Beitrag fasst die Ergebnisse der insgesamt vier Sitzungen der Ad‐hoc‐Gruppe zusammen, die im Laufe des Jahres 2015 veröffentlicht werden sollen. [ABSTRACT FROM AUTHOR]

Hochduktiler Beton ist ein mit kurzen Kunststofffasern bewehrter Hochleistungsverbundwerkstoff auf Zementbasis, der unter Zugbelastung eine hohe nichtelastische Verformbarkeit und ein verfestigendes Materialverhalten aufweist. Der alleinige Einsatz von Fasern als Bewehrung ist im konstruktiven Ingenieurbau jedoch auf wenige Anwendungsgebiete beschränkt, sodass in tragenden Bauteilen eine Kombination von hochduktilem Beton und konventioneller Stahlbewehrung erforderlich wird. Das Zusammenwirken beider Bewehrungsarten soll ein günstiges Trag‐ und Verformungsverhalten von zugbeanspruchten Bauteilen herbeiführen. Die rissüberbrückende Wirkung der Fasern führt dabei zu einer deutlichen Steigerung der Tragfähigkeit und hat durch die geringen Verformungen im Zustand II einen günstigen Einfluss auf die Gebrauchstauglichkeit. Des Weiteren werden durch das Zusammenwirken von Fasern und Stahlbewehrung die Rissbreiten deutlich reduziert und dadurch eine wesentliche Verbesserung der Dauerhaftigkeit erzielt. Um diese Zusammenhänge im bauwerkrelevanten Maßstab nachzuweisen und zu analysieren, wurden einaxiale Bauteilzugversuche durchgeführt, auf deren Basis das globale und lokale Zugtragverhalten der großformatigen Verbundkörper beschrieben werden kann. In diesem Beitrag werden die Ergebnisse der experimentellen Untersuchungen dargestellt und Schlussfolgerungen in Bezug auf die Bemessung und Konstruktion von zugbeanspruchten Stahlbetonbauteilen aus hochduktilem Beton gezogen. Structural behaviour of steel‐bar‐reinforced SHCC elements subjected to tensile loading Strain‐hardening cement‐based composite (SHCC) is a high‐performance cementitious material which exhibits high, non‐linear deformation capabilities and strain‐hardening behaviour under tensile loading. This behaviour is achieved by utilizing micro‐mechanical effects which induce multiple cracking by bridging cracks with polymer fibres. The goal of the research work at hand is to acquire a deeper understanding of the interaction between steel reinforcement and SHCC under tensile loads. The mechanical interrelation between these two materials is governed by the tensile‐deformation behaviour of both steel and SHCC and the bond between them as well. The material properties and their combined influence on the global and local deformation behaviour of structural members under tensile load were analysed in order to enable the sustainable, efficient design of structures made of steel‐reinforced SHCC (R/SHCC). A series of large‐scale uniaxial tension tests was carried out to investigate the influence of the reinforcement ratio on the deformation and cracking behaviour of R/SHCC elements. The results showed that the load bearing‐deformation characteristics of the elements under tensile load is governed by the multiple‐cracking behaviour of the SHCC after initial cracking. It could be concluded that the multiple cracking of SHCC enhances the load‐bearing capacity of the slab in comparison to slabs made of ordinary RC and prevents the development of large cracks, even at low reinforcement ratios. [ABSTRACT FROM AUTHOR]

Exterior concrete components that have to fulfill a sealing function next to their load transfer, reinforcing or room-enclosing function require accuracy in planning, execution and subsequent injection measures alike. To ensure functionality of watertight concrete structures, sealing injections that also guarantee protection from reinforcement corrosion are necessary. Constructive and executive measures as well as concrete technology cannot entirely prevent concrete from cracking. During curing, load or other exposition to stress, cracks with unacceptable width or even water bearing cracks may occur. Permanent sealing can be achieved using special and tailor made injection materials. Cavities and defects in concrete cross sections caused during the production process may appear only to a limited extent and are furthermore limited in frequency and dimension. Boundary layers either among structural parts or between concrete and reinforcement or mounting parts are partially affected by cavity building. Cavities may be sealed by laminar injection measures. Injection measures have to fit the concrete construction. Their successful execution requires knowledge about construction and execution. German rules and standards for refurbishing measurements are influenced significantly by European harmonization. Consideration of current standards and regulations is compulsory. [ABSTRACT FROM AUTHOR]

Zur Beurteilung des Frost- bzw. Frost-Tausalz-Widerstandes des Betons finden normativ als Alternativverfahren das CIF- bzw. CDF-Verfahren Anwendung. Als Beurteilungskriterium für den inneren Schädigungsprozess werden bisher ausschließlich die Änderung der Ultraschalllaufzeit und die Massezunahme durch Frostsaugen herangezogen. Die Bewertung des äußeren Schädigungsprozesses hingegen erfolgt ausschließlich mittels einer vergleichenden visuellen Beurteilung der Prüffläche und der Ermittlung der Abwitterungsmasse. Allen bisher angewandten inneren und äußeren Schädigungsindikatoren ist gemeinsam, dass ihre Aussagefähigkeit durch eine fehlende ortsaufgelöste Quantifizierung des Schädigungsprozesses eingeschränkt ist. Der Beitrag zeigt, dass dieser Nachteil durch den Einsatz neuartiger innovativer Prüftechniken weitestgehend beseitigt werden kann. So wird vergleichend zu der normativen Ultraschallprüfung aufgezeigt, dass der Einsatz der Röntgen 3D-Computertomografie eine zerstörungsfreie zeitliche und räumliche Analyse des inneren Rissbildungsprozesses beim CIF-Verfahren ermöglicht. Außerdem wurde durch die Anwendung der Photogrammetrie die äußere Abwitterung der Prüffläche beim CDF-Verfahren erstmalig ortsaufgelöst quantifiziert. Analysis of damage processes in concrete induced by freeze thaw or freeze thaw salt cycles. Application of innovative measurement techniques CIF- and CDF-test are alternatively applied for the standardized assessment of freeze and freeze de-icing salt resistance of concrete. Up to now the increase of ultrasonic time of flight and mass induced by freeze suction are the only criteria for the assessment of internal damage process. The evaluation of the external damage process is currently realised by visual comparison of test surfaces and the determination of the scaling mass. The significance of these internal and external damage indicators is limited due to the lack of spatially-resolved quantifications of the damage process. This contribution shows that this disadvantage can be overcome by the application of innovative test methods. In contrast to normative ultrasound test methods, the application of X-ray 3D computed tomography allows a non-destructive temporal and spatial analysis of the internal crack formation process during the CIF-test. For the first time, a spatially-resolved quantification of the scaling of the test surface has been performed by photogrammetry. [ABSTRACT FROM AUTHOR]

Zur Beurteilung der Alkaliempfindlichkeit der Gesteinskörnung finden normativ der Betonversuch mit Nebelkammerlagerung bei 40 °C und alternativ der 60 °C-Betonversuch Anwendung. Als Beurteilungskriterium für den Schädigungsprozess wird bei beiden Verfahren die an Betonprismen diskontinuierlich ermittelte Dehnung herangezogen. Auch bei den zusätzlich in der Nebelkammer gelagerten Würfeln beschränkt sich die Schadensanalyse auf eine diskontinuierliche Verfolgung der maximalen Breite der Oberflächenrisse. Im Rahmen des Beitrags wird eine neuartige, bereits erfolgreich erprobte zerstörungsfreie Prüfmethodik vorgestellt. Diese ermöglicht durch eine gleichzeitige kontinuierliche Dehnungs-, Schallemissions- und Ultraschallmessung eine kontinuierliche Verfolgung der inneren Gefügeveränderungen in den Betonprüfkörpern während der AKR-provozierenden Lagerung. Dabei wurden drei zeitlich aufeinanderfolgende Phasen der inneren Gefügeveränderung mit einer Dominanz von Hydratation, Rissbildung sowie vermutlicher Rissverfüllung mit Reaktionsprodukten identifiziert. Die ablaufenden Rissbildungsprozesse wurden zusätzlich mit diskontinuierlich durchgeführten röntgentomografischen Untersuchungen zeitlich und räumlich visualisiert. Die CT-Befunde wurden durch mikroskopische Untersuchungen bestätigt. Analysis of ASR-induced damage processes in concrete Application of innovative measurement techniques The alkali-reactive potential of aggregates is assessed according to the German guidelines by two different test methods. These are the 40 °C fog chamber storage and as an alternative method the 60 °C concrete prism test. In both tests, the discontinuously measured expansion of ASR-generating stored concrete prisms is used as criterion for the internal damage process. The damage analysis of the cubes additionally stored in the 40 °C fog chamber is also restricted to the discontinuous measurement of the crack width on the cubes surfaces. This paper describes an innovative, already successfully applied, non-destructive measurement methodology. This methodology enables a continuous monitoring of the internal damage processes in ASR-generating stored concrete specimens due to a continuous recording of expansion, acoustic emission and ultrasonic velocity. Thereby, three sequent phases of internal structural changes dominated by hydration, crack formation and filling of the cracks with ASR-gel and/or other reaction products can be detected. The crack formation was temporally and spatially visualised by discontinuously applied X-ray computed tomography measurements. Microscopic analyses confirm the findings of the X-ray 3D-CT. [ABSTRACT FROM AUTHOR]

Die Ausführung von unbeschichteten, direkt befahrenen Bodenplatten ist eine nach den aktuellen Normen und Merkblättern anerkannte Bauweise, wenn zum einen ein möglichst chloriddichter Beton bei ausreichend hoher Betondeckung verwendet wird. Zum anderen sollten Maßnahmen ergriffen werden, um die Rissbildung zu vermeiden bzw. sollte eine 'begleitende Rissbehandlung' im Rahmen der Wartung durchgeführt werden. Die Erfahrungen an insgesamt vier durch einen Fachplaner gutachterlich begleiteten Bauvorhaben zeigen, dass sowohl die Chloriddichtheit nachweisbar erreicht werden kann, als auch eine weitestgehende Rissfreiheit, selbst nach mehreren Wintern, eingehalten ist. Entscheidend für den Erfolg der rissfreien Konstruktion ist, dass bereits in den frühen Planungsphasen eine zwängungsarme Auflagerung berücksichtigt wird. Zudem sind auch ein ausreichendes Gefälle sowie die Konzeption von Entwässerungseinrichtungen frühzeitig planerisch zu berücksichtigen. Die Ausführungsqualität der Bodenplatte kann mittels zerstörungsfreier Betondeckungsmessungen und durch Bestimmung der Chloridbelastung überprüft werden. Letztlich konnte mit den hier beschriebenen, unbeschichteten Tiefgaragen-Bodenplatten eine dauerhafte und wirtschaftliche Konstruktion gefunden werden, deren Instandhaltungsaufwand im Vergleich zu beschichteten Bodenplatten deutlich geringer sein wird. Uncoated and directly driven RC-ground slabs in underground car parks - a field report The construction of an uncoated and directly driven RC-ground slab is proven and acknowledged by standards and bulletins, if on one hand a concrete is used, which is chloride dense as possible in combination with a sufficient thick concrete cover. On the other hand actions should be taken to avoid crack initiation or an accompanied crack treatment within the scope of the maintenance should be carried out. The experience of four building projects, which were supervised by concrete technology consultants, show, that as well the chloride impermeability is verifiable achievable as hardly any cracks have been determined - even after several winter periods. Important to achieve a crack-free construction is the consideration of a bearing with reduced restraints already in early stages of the design. Also the planning of a sufficient gradient of the surface and a drainage concept has to be considered early within design. The quality of the execution of the ground slab can be checked by using non destructive concrete cover measurement and by determining the chloride contamination. Finally a durable and cost-effective construction could be achieved with the described uncoated subterranean garage ground slabs leading to a reduced maintenance expense compared to coated ground slabs. [ABSTRACT FROM AUTHOR]

Ingenieurbauwerke sind im Laufe ihres Lebens ständig statischen und dynamischen Lasten ausgesetzt. Diese haben sowohl künstliche wie auch natürliche Ursachen. Durch die dynamische Belastung kann es an Betonbauwerken zu Ermüdungserscheinungen kommen. Die Änderungen in der Betonmatrix, die mit diesen Ermüdungserscheinungen einhergehen, sind noch nicht vollständig untersucht. Bei den Fundamenten für Windenergieanlagen im Bereich On- und Offshore stellt die Materialermüdung eine besondere Herausforderung dar. Die Lastkombinationen, welche für die Ermüdungsnachweise angenommen werden, sind oft bemessungsmaßgebend. Da eine Spannungsumlagerung innerhalb des Querschnitts beim Nachweis nicht berücksichtigt wird, hat dies zur Folge, dass die zu bemessende Betonstruktur sehr konservativ ausgelegt wird beziehungsweise über die Lebensdauer ein höherer Schädigungsgrad angenommen wird, als er in der Realität vorliegt. Ein Ziel der Forschungen ist die Entwicklung eines Monitoringsystems, mit welchem der wirklich vorhandene Schädigungsgrad einer Betonstruktur abgelesen werden kann. Das Strabag-Testfundament in Cuxhaven, gebaut von der Ed. Züblin AG, stellt eine optimale Möglichkeit dar, dieses Monitoringsystem an einer Betonstruktur mit realen Dimensionen zu testen. Die Durchführung der Ermüdungsversuche am Testfundament Cuxhaven sind für Anfang 2013 geplant. Die vorliegende Veröffentlichung ist wie folgt gegliedert: Nach einführenden Worten über den Sachverhalt Betonermüdung und Offshore werden die Konzeption der Versuchsdurchführung, die geplante dynamische Erregung des Testfundamentes und erste Ergebnisse der nichtlinearen Modellbildung des Testfundamentes in der FE-Software ATENA vorgestellt. Experimental modelling of fatigue processes to detect the real degree of deterioration. Conceptual design of the fatigue tests at the Strabag-Gravity base in Cuxhaven Engineering structures are subjected to continuous and increasing static and dynamic loads from artificial and natural environmental conditions (e.g. wind, traffic loads or wave loading on offshore wind turbine structures). Dynamic Loads can result in fatigue phenomena within the material concrete which are not totally explored even in their beginnings. Especially in the fields of Foundations for wind energy plants on- and offshore fatigue is a big problem. The Fatigue associated load combinations are mostly the decisive ones for design and dimensioning of the structure. The targets of the research are the development of a monitoring system for detecting the initiation or the early stage of a fatigue process in concrete and for the identification of the degree of deterioration in the concrete structure. The full scale model of a new type of gravity base foundation for offshore wind turbines in Cuxhaven projected by the Ed. Züblin AG is an optimal possibility to test the monitoring system within a concrete structure of real dimensions. The objective of this contribution is to provide a short review of concrete fatigue properties, to discuss, demonstrate and portray preliminary analyses results which are decisive for the final fatigue test layout at the Strabag gravity base foundation in Cuxhaven. The conduction of the fatigue tests at the gravity base foundation are planned in the beginning of the year 2013. [ABSTRACT FROM AUTHOR]