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Several studies show that thermal and hydrothermal treatment can further improve the excellent properties of UHPC in terms of mechanical strength and durability. While for the thermal treatment the increase in strength is attributed to an intensified pozzolanic and hydraulic reaction, for the hydrothermal treatment previous studies accredited it mostly to the formation of tobermorite. In the presented study thermal and hydrothermal treatment of UHPC samples was systematically varied and the phase formation analysed related to the strength development of a reference sample cured for 28 days in water. For the thermal treatment the results show that the strength increase depends on the protection against desiccation and can be ascribed to an improved pozzolanic reaction of the siliceous fillers. To achieve a significant enhancement of strength, a pre-storage time of few days and a long dwell time at elevated temperature/pressure are required. For the hydrothermal treatment already heating the specimens up to 185 °C in saturated steam followed by an immediate cooling leads to a substantial increase in compressive strength. Pre-storage time did not affect the result as far as a minimum of several hours is guaranteed. The improved performance is due to an increase in the pozzolanic and hydraulic reaction. Surprisingly, tobermorite was only found within a very thin layer at the surface of the sample, but not in the bulk. Sulphate and aluminium stemming from the decomposition of the ettringite are bound in the newly formed phases hydroxylellestadite and hydrogarnet.

Recently, a growing demand for geothermal applications has led to the exploitation of energy efficiently by developing grouting materials in the borehole between pipes and the ground. Therefore, the current study developed newly formulated cementitious grouts by the integration of expanded graphite (EG)-based hybrid additives synthesized by building chemical bridges between silica particles and EG in the presence of amino functional silane coupling agents. These produced hybrid additives with controlled EG and silica ratios were utilized in grout mixtures used in borehole heat exchangers to enhance the thermal conductivity. According to the optimization study on the formulation development of grout mixtures with bentonite, silica sands, cement, and superplasticizer by adding neat EG and EG-based hybrids, the relationship between the carbon amount and water demand was found to have a significant impact on thermal conductivity. The highest thermal conductivity value of 2.656 W/mK was achieved by the incorporation of 5 wt% hybrid additive with the ratio silica/EG of 1:5 compared to the reference grout, which showed a thermal conductivity of 2.373 W/mK. Therefore, the enhancement in thermal conductivity was dependent on the increase in the EG content and also the additive loading ratio, resulting in a slight increase in the water demand.

This work evaluates the effects of newly designed graphene/silica hybrid additives on the properties of cementitious grout. In the hybrid structure, graphene nanoplatelet (GNP) obtained from waste tire was used to improve the thermal conductivity and reduce the cost and environmental impacts by using recyclable sources. Additionally, functionalized silica nanoparticles were utilized to enhance the dispersion and solubility of carbon material and thus the hydrolyzable groups of silane coupling agent were attached to the silica surface. Then, the hybridization of GNP and functionalized silica was conducted to make proper bridges and develop hybrid structures by tailoring carbon/silica ratios. Afterwards, special grout formulations were studied by incorporating these hybrid additives at different loadings. As the amount of hybrid additive incorporated into grout suspension increased from 3 to 5 wt%, water uptake increased from 660 to 725 g resulting in the reduction of thermal conductivity by 20.6%. On the other hand, as the concentration of GNP in hybrid structure increased, water demand was reduced, and thus the enhancement in thermal conductivity was improved by approximately 29% at the same loading ratios of hybrids in the prepared grout mixes. Therefore, these developed hybrid additives showed noticeable potential as a thermal enhancement material in cement-based grouts.

In the framework of the European project H-House various concrete façade elements were developed with the aim to ensure a long service life by combining a very durable material with selfcleaning properties. The façade elements presented are made of a shell of UHPC filled with blocks of aerated autoclaved concrete as insulating material. Self-cleaning properties were realized amongst others by imprinting a microstructure into the surface during casting. The paper focuses on selected technological aspects of the manufacturing process of prototypes which had to be performed in two concreting sections. Furthermore the challenges faced when upscaling the self-cleaning properties are addressed and the strategy to assess the self-cleaning properties by measuring the contact and the rolloff angel is presented. The results show that a successfull upscalaing process requires detailed planning and that the best results can often be achieved with a moderate work effort or material use.

By the combination of an optimized granulometry, a reduced water?cement ratio and the use of superplasticizers ultra-high performance concrete achieves a compressive strength of over 150 N ...

The aim of this study was to develop a lightweight composite facade element for new buildings and for the refurbishment of existing facades. These composite elements have been developed combining an insulation layer of autoclaved aerated concrete (AAC) with an external ultrahighperformance concrete (UHPC) supporting layer. This solution allows avoiding the use of connectors and facilitates the production procedure. The structural behavior of the facade elements is mainly influenced by the presence of the upturning edges that are able to increase the stiffness of the element and reduce the thickness of the external layer. The insulation material has no influence on the structural behavior of the UHPC boxes. Flexural tests were carried out to investigate a potential detachment of the external layer from the upturning edge. The photogrammetric Analysis used during the flexural tests essentially confirmed that the bond between the two UHPC layers cast in two steps is reliable. The quality of the bond between the external layer and the upturning edge is a key parameter to define the bearing capacity of the element.

This paper focuses on the experimental evaluation of one of the key microstructural parameters of a short-fiber reinforced composite – the orientation distribution of fibers. It is shown that computed tomography (CT) produces results suitable for reconstruction of the orientation distribution function. This function is used for calculation of the effective elastic properties of polymer-fiber reinforced concrete. Explicit formulas are derived for overall elastic moduli accounting for orientation distribution in the frameworks of the non-interaction approximation, the Mori–Tanaka–Benveniste scheme, and the Maxwell scheme. The approach illustrated can be applied to any kind of composite material.

In diesem Beitrag werden numerische Analysen der mechanischen Eigenschaften von Lehmsteinmauerwerk unter Druck- und Schubbeanspruchung vorgestellt. Ergebnisse von einachsigen Druck- und Schubversuchen an Wandprufkorpern lieferten dafur grundlegende mechanische Kennwerte im elastischen Bereich und im nichtelastischen Versagenszustand.Die Testergebnisse zeigten, dass verschiedene Vorlasten keinen wesentlichen Einfluss auf die Schubfestigkeit haben. Auserdem bestatigten die Ergebnisse das sprode Verhalten von Lehmsteinmauerwerk unter einachsiger Druckbelastung und es zeigte sich, dass das Versagen des Lehmsteinmauerwerks unter Scherbelastung entlang der Mortelfugen erfolgt. Die experimentellen Ergebnisse wurden verwendet, um das Verhalten von Lehmsteinmauerwerk durch nichtlineare Finite-Elemente-Methoden auf der Basis von Makro- und Mikro-Modellierungsansatzen zu simulieren. Entsprechendes konstitutives Materialverhalten und Zwangungen, die in den Versuchen durch die Art der Lasteinleitung in Form von Stahlprofilen und Stahlschuhen verursacht wurden, wurde in den Modellen berucksichtigt. Es wurde zuerst ein auf der Grundlage der experimentellen Daten kalibriertes Makro-Modell entwickelt, was zu einer brauchbaren Vorhersage des Versagensverhaltens der Mauerwerksprufkorper fuhrte. Die simulierten Spannungs-Dehnungs-Kurven, berechnet unter einachsiger Druckbelastung, zeigten eine gute Ubereinstimmung mit den Ergebnissen der gepruften Mauerwerkskorper, sowohl im elastischen als auch im nichtelastischen Bereich. Ein vereinfachter Ansatz, basierend auf der Makro-Modellierung und einem homogenisierten Prufkorper, kann fur die Untersuchung groserer Tragsysteme oder ganzer Gebaude angewendet werden, wobei eine zufriedenstellende Genauigkeit bei geringerem Rechenaufwand erreicht wird. Obwohl das globale Spannungs-Dehnungs-Verhalten zufriedenstellend wiedergegeben wurde, ist ein solches nichtlineares isotropes Kontinuumsmodell fur Lehmsteinmauerwerk nicht in vollem Umfang geeignet, um das bei den Versuchen beobachtete Rissbild an den Prufkorpern zu simulieren. Eine detailliertere Analyse des mechanischen Verhaltensdes Mauerwerks wurde mit einem Mikro-Modellierungsansatz durchgefuhrt. Das Modell, in dem ein Wandabschnitt nicht mehr homogenisiert, sondern in konkrete Stein- und Fugenelemente diskretisiert wird, hat sich insbesondere fur das Verhalten von Lehmsteinmauerwerk unter Schubbeanspruchung als geeignet erwiesen. Die Auswertung der Spannungsverteilungen bei der nichtlinearen Analyse lieferte Informationen uber die tatsachlichen Mechanismen der Lastubertragung zwischen Steinen und Mortelfugen. Mit dem Mikro-Modell war es moglich, das nichtlineare Verhalten von Lehmsteinmauerwerk vorherzusagen. Es stellt somit ein geeignetes Werkzeug fur die Untersuchung der Versagensmechanismen von Lehmsteinmauerwerk dar. Allerdings sind aufgrund der Komplexitat des Modells fur die Beschreibung der Stein/Mortel-Schnittstelle und die hohe Anzahl an erforderlichen mechanischen Parametern umfassendere Untersuchungen notwendig. Die zukunftige Forschung wird sich daher einerseits auf die Verfeinerung der numerischen Modelle und andererseits auf die Simulation komplexer Belastungssituationen und Gebaudekomponenten konzentrieren.

The European building sector is moving towards more complex and high-tech building approaches. While focusing on energy efficiency, aspects, e.g. occupant health, sustainability and life-cycle costing are often neglected. This study highlights the potential of earthen plasters in combination with natural ventilation for low-tech solutions. The EU-funded project [H]house established the outstanding performance of earthen materials in light of hygrothermal and air-purifying properties, which were further supported by experimental data from monitoring of naturally ventilated pilot buildings in Berlin. Additionally, [H]house demonstrated through LCC an increased cost-efficiency of earth-based low-tech solutions in comparison with conventional constructions relying on mechanical ventilation.

The study presents the results from the development of a grouting material based on hydrated lime with addition of pozzolana, which is referred to as hydraulic lime, suitable for the repair of cracks in a variety of earthen building techniques. The goal was to develop a material also compatible with earthen structures exposed to dynamic loads. The grouting mortar was designed to be adaptable in strength properties and at the same time to have sufficient robustness for preparation and use on the construction site. Results showed a satisfactory performance of the grout concerning fresh and hardened mortar properties as well as injectability.

The current paper focuses on the determination of reliable numerical models of earth block masonry wallettes under different loading conditions. Uniaxial compression and diagonal compression tests were performed. Experimental behaviour was modelled with a non-linear model able to describe the cracking behaviour. The simplified approach based on macro-modelling shows a satisfactory accuracy and low computational costs. The results reproducing the uniaxial compression are in good correspondence with the post-elastic behaviour observed in the experimental campaign. The micro-modelling approach adopted to reproduce the shear behaviour, even with high computational cost, represents a suitable tool to predict the masonry collapse mechanism. (C) 2015 Elsevier Ltd. All rights reserved.

In this paper results of the experimental testing performed on brick masonry and earth block masonry are presented. The paper outlines the development of the testing procedures for two different types of anchors. For this purpose, two experimental campaigns of pull-out tests on masonry corner connections strengthened by metallic rod grouted were carried out. Experimental results proved that the implemented testing procedures are suitable to determine the most recurring failure modes of the anchor pins. Moreover, a procedure is proposed to estimate the capacity of grouted anchor pins based on experimental studies. Mit diesem Beitrag soll die experimentelle Beurteilung von Verpressankern fur Mauerwerk vorgestellt werden. Es wurden zwei Versuchsserien mit Ankerauszugsversuchen an Mauerwerksecken aus Ziegel- und Lehmsteinmauerwerk durchgefuhrt. Die Versuchsergebnisse haben gezeigt, dass die gewahlten Versuchsablaufe geeignet sind, die am haufigsten wiederkehrenden Versagensarten der Verpressanker zu bestimmen. Daruber hinaus wird eine Vorgehensweise vorgeschlagen, die es ermoglicht, die Traglast von Verpressankern auf Basis experimenteller Untersuchungen abzuschatzen.

Earth represents one of the oldest construction materials, which is still utilised both in developed and in developing countries. In this paper a comparison of the mechanical performance of structural elements built in three basic techniques, earth block (adobe) masonry, rammed earth and cob, is presented. In order to gain better knowledge on the structural behaviour under static loads an extensive compression and diagonal compression (shear) test campaign was performed. First compression results showed brittle mechanical behaviour in the case of earth block masonry and rammed earth elements, whereas cob exhibited a very different stress–strain pattern: cob can deform beyond the elastic range with a gradual drop in capacity. Despite its low compressive strength, cob thus presents a relatively good performance within the earthen material range as far as shear behaviour is concerned. The data here reported represents a base for a further investigation on the dynamic behaviour of the three materials considered. The study was carried out within the framework of the project NIKER funded by the European Commission dealing with improving immovable Cultural Heritage assets against the risk of earthquakes.

The goal of the present study is to assess the feasibility to develop a first reliable database of materials parameters for Earth Block Masonry (EBM). The database is crucial when defining the materials safety factors. In the first part an experimental campaign of compressive tests were carried out on two types of earth block and two types of earth mortar. The results showed that the mean variation of the compressive strength was remarkably less than expected. This low variation is related to a production with high quality standards of the materials employed. In the second part a partial safety factor for EBM under uniaxial compression was determined through the reliability method. The results proved the reliability of a common calculation method for EBM based on partial safety factors following the current standards.

Pozzolana–lime mortars modified with water-repellent admixtures were designed and studied to obtain mortars for restoration application. Powdered silane and calcium stearates were mixed with pozzolana, lime and sand and the chemical–physical properties of the resulting mortars were evaluated by X-ray diffraction, electron microscopy (SEM-EDX), thermogravimetric analysis and FT-IR spectroscopy. The mechanical behavior, the pore structure and the hygric behavior were measured. The resistance of water-repellent mortars to the salt crystallization was evaluated. Both calcium stearates and powdered silane allowed good water-repellent protection even if the water-repellent agents and their dosage modified some physical properties and the hydration kinetic.

Das Wissen uber die Materialeigenschaften und die Versagensmechanismen bei Lehmbaustoffen ist begrenzt und luckenhaft. Im Rahmen des EU-Projekts NIKER (www.niker.eu) wurden deshalb die mechanischen Eigenschaften von Bauteilen aus Lehm unter statischer Druck- und Schubbeanspruchung bestimmt. Ziel der Untersuchungen war es, grundlegende Daten zum Verformungs- und Versagensverhalten von Lehmbauteilen zu erhalten und dieses mit einem numerischen Modell zu beschreiben. Die Versuchsergebnisse belegten das sprode Verhalten von Lehmsteinmauerwerk bei uniaxialer Druckbelastung und zeigten, dass das Versagen von Lehmsteinmauerwerk infolge Schubbelastung nach Erstrissbildung in Mortelfugen und Lehmsteinen durch Gleiten der Lehmsteine entlang der Mortelfugen erfolgt. Die numerische Makromodellierung erbrachte zwar befriedigende Resultate hinsichtlich des Spannungs-Dehnungs-Verhaltens, jedoch konnte bei der simulierten Rissbildung keine Ubereinstimmung mit den in den Versuchen beobachteten Rissbildern erzielt werden. Bei Lehmsteinmauerwerk ist also eine wesentlich aufwendigere Mikromodellierung notwendig, um das Versagensverhalten korrekt beschreiben zu konnen. Knowledge of the material properties and failure mechanisms of earthen materials is limited and scattered. Within the framework of the NIKER project (www.niker.eu) funded by EC, the mechanical properties of earthen material elements were therefore determined under static compression and shear loads. The aim was to obtain fundamental data on deformation behaviour and failure mechanisms of earthen material structural elements and to describe them by means of a numerical model. The test results confirmed the brittle behaviour of earth block masonry under monoaxial compressive load and showed that the failure of earth block masonry under shear load occurs by sliding of the earth blocks along the mortar joints after initial cracking in mortar joints and earth block. Numerical macro modelling showed satisfying results with regard to stress-strain behaviour, but the simulated crack pattern was not consistent with experimental observations. In the case of earth block masonry, it is thus necessary to use micro modelling approaches in order to correctly predict the failure process at local level.

Es werden drei Pruefverfahren verglichen, die eine Beurteilung der Wirksamkeit von Faserzugaben zum Beton zur Reduzierung der Schrumpfrisse erlauben. Anhand der Versuchsergebnisse werden dann die Vor- und Nachteile benannt und diskutiert. Die Beigabe von Fasern ist eine von mehreren Methoden, um Schrumpfrissbildungen im Beton zu vermindern. Ist diese Wirkung nachzuweisen, wird eine experimentelle Beurteilung erforderlich. Die Pruefverfahren, die sich im Hinblick auf die Durchfuehrung unterscheiden, finden sich in verschiedenen Normen und Richtlinien. Aus den moeglichen Verfahren wurden fuer den Vergleich drei Verfahren ausgewaehlt. Es handelt sich um das Pruefverfahren des Deutschen Instituts fuer Bautechnik (DIBt) zur Zulassung von Fasern als Betonzusatzstoff, das Pruefverfahren nach der Richtlinie Faserbeton der Oesterreichischen Vereinigung fuer Beton und Bautechnik (OEVBB) und das Pruefverfahren nach der Amerikanischen Pruefvorschrift ASTM C 1597. Die Versuchsanordnungen und -bedingungen sowie die Versuchsdurchfuehrung dieser drei Verfahren werden beschrieben. Fuer die durchzufuehrenden Versuche wurden zwei verschiedene Betongrundrezepturen (B1 und B2) mit verschiedenen Zementen und unterschiedlichem Wasser-Zement-Wert hergestellt. Bei den zugegebenen Fasern handelte es sich um Polypropylenfasern mit rechteckigem Querschnitt. Mit den Betonmischungen wurden sowohl unbewehrte als auch faserbewehrte Probekoerper hergestellt. Die Betongrundrezeptur B1 diente zur Herstellung der Versuchsplatten fuer die Pruefung mit dem DIBt-Verfahren, waehrend die Pruefung nach der OEVBB-Richtlinie an Probekoerpern aus der Betonmischung B2 erfolgte. Fuer die Pruefungen der mit der Betonmischung B1 hergestellten Versuchsplatten nach ASTM wurde ein neu entwickelter Versuchsaufbau benutzt, der bei den Versuchen im Windkanal einen gleichmaessigen Luftstrom ueber die Oberflaeche der Platten gewaehrleistet. Zusammenfassend wird festgestellt, dass grundsaetzlich alle drei Verfahren zur Beurteilung der Wirksamkeit von Fasern zur Verminderung der Schrumpfrissbildung geeignet sind. Die Art des erzeugten Luftstroms kann sich jedoch nachteilig auf die Reproduzierbarkeit der Ergebnisse auswirken. Des Weiteren wird empfohlen, zusaetzlich zur visuellen Beurteilung der Rissbildung eine Quantifizierung durch Rissvermessung vorzunehmen. Die Einfuehrung eines Rissminderungsbeiwertes auf der Basis der Rissflaechen wird vorgeschlagen; einschliesslich eines minimalen Rissminderungsbeiwertes als Kriterium zum Nachweis der Wirksamkeit der Fasern. Weitere Empfehlungen beziehen sich auf die Mindestrissbreite in den unbewehrten Referenzplatten, die Verdunstungsrate, die Pruefdauer und die Messung des plastischen Schwindens.

In this paper, a comparative study on the initial shear strength of masonry with earth mortars is presented. Triplet tests were carried out to characterise the shear bond strength of five different types of earth mortar, three purely mineral and two with vegetable additives (wood and straw chaff), using calcium silicate blocks. In spite of their lower bulk densities, mortars with chaffs reached a value of compressive strength comparable to the values shown by the purely mineral mortars. The characteristic initial shear strengths of all the tested earth mortars were between two and five times higher than the minimum values for initial shear strengths required by standards. To assess the influence of blocks pre-wetting, a comparison between calcium silicate blocks and earth blocks was performed to evaluate the results obtained from the standard test procedure compared to the more common practice of using earth mortars in combination with earthen blocks.

Zu den Zielen der Nanotechnologie gehort die Entwicklung, Produktion und Anwendung von Materialien und Werkstoffen mit vollig neuartigen Leistungsspektren. Fur die Baupraxis und die Materialforschung lassen sich uber den Einsatz der Nanotechnologie Ziele wie die Optimierung von Baustoffeigenschaften, Vermeidung von Schaden und neue Funktionalitaten definieren. Der vorliegende Beitrag gibt einen Uberblick uber mogliche Anwendungsbereiche der Nanotechnologie im Bausektor, wie z. B. zementgebundene Baustoffe, Ausen- und Dachfassaden, Fenster und Verglasungen, Brandschutz, Inneneinrichtung und Infrastrukturbau. Zudem werden aktuelle Forschungsarbeiten mit nanowissenschaftlichem und nanotechnologischem Schwerpunkt im Bereich baustoffbezogener Materialien der Bundesanstalt fur Materialforschung und -prufung (BAM) in Berlin vorgestellt. Die Forschungstatigkeiten beziehen sich zum einen auf die Modifikation der Hydratphasen in Ultra-Hochleistungsbeton (UHPC) und zum anderen auf die Weiterentwicklung von Anti-Graffiti-Systemen. Nanotechnology in Construction Engineering In general, nanotechnology comprises the development, production and application of materials yielding novel functionalities and performances. In the construction industry and materials research nanotechnology can be utilized for a variety of areas of application, such as the optimisation of material properties, the prevention of damages and the implementation of new functionalities. This article gives an overview of areas in the construction sector where nanotechnology gains prominently of significance, such as cementitious binders, facades, windows and glazing, fire protection, interior decoration and infrastructure buildings. Furthermore, actual scientific research activities in the field of building materials on a nano-scale performed by the Federal Institute for Materials Research and Testing (BAM) in Berlin are being presented. The research activities relate to the modification of hydrate phases in ultra high performance concrete (UHPC) and to the enhancement of performance of anti-graffiti-systems.

Ziel der Untersuchungen war es, das Verhalten von Verpressankern zu analysieren, die ublicherweise zur Verstarkung der Eckverbindung von Mauerwerkswanden eingesetzt werden. Im Fokus der Untersuchungen stand die Leistungsfahigkeit der Ankersysteme mit Bezug auf die Versagensarten und auf dem Traglastvermogen der Anker bei Ankerauszug durch gleichformige Zugbelastung, die als Vereinfachung fur die dynamische Belastung durch ein Erdbeben aufgebracht wurde. Die hier dargestellten Untersuchungen und Ergebnisse stellen eine Zusammenfassung von Arbeiten dar, uber die bereits in Beitragen berichtet wurde, die zum einen die Prufverfahren fur verstarkte Eckverbindungen von Gebauden aus Mauerwerk und zum anderen die Verbundfestigkeit von Verpressankern in Wanden aus verschiedenen Lehmbautechniken zum Inhalt hatten. Sie geben dennoch einen Uberblick uber die Hauptversagensmechanismen von Verpressankersystemen und erweitern den Wissensstand bezuglich der Prufung von Ankersystemen fur Ziegel- und Lehmsteinmauerwerk. Daruber hinaus wird eine Vorgehensweise vorgeschlagen, die es ermoglicht, die Traglast von Verpressankern auf Basis experimenteller Untersuchungen abzuschatzen.

Water-repellent mortars were prepared using different hydrophobic compounds as admixtures. Calcium and zinc stearates, silane/siloxane products (as liquid solution and powder) were mixed into limestone cement mortars for obtaining in-bulk water-repellent mortars suitable for building protection and resistant to the degrading action of water. The influences of the admixtures on the hydration and structure of the designed mortars were investigated by SEM, TG–DSC, FT-IR, XRD, and isothermal calorimetry. The effectiveness of these agents against water action was evaluated by using techniques and methods such as mercury intrusion porosimetry, water absorption tests and contact angle measurements. Siloxane products conveyed good water-repellent effectiveness, without strongly influencing the setting and hydration of the binder, while the zinc stearates slowed down the hydration reactions.

Der Einflus der Mischungszusammensetzungen auf das fruhe 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.

A new rule-based spectra interpretation system is described. It directly processes spectral files generated by spectrometers. Its internal information representation and the simultaneous use of several spectroscopic methods allow for the achievement of both high reliability and good performance. For small and medium sized molecules, the new program is capable of automatically reducing the solution space to under 3%.

Assemble 2.0, a new structure generator with a user-friendly interface is presented. The pieces of structural information that can be input are reviewed and an example of the achievable results in a fully automatic mode of operation is given. The generated structures can be ranked automatically on the basis of their 1 H and/or 13 C NMR spectra. The program is available for Windows 95, Windows 98, and Windows NT.

We present an all-atom force field model for liquid carbon tetrachloride for use in molecular dynamics simulations. The model is rigid with tetrahedral symmetry and the molecular interactions are represented in terms of site-site Lennard-Jones potential energy functions. With the molecular dynamics method we are able to accurately predict physical quantities of CCl4 including shear viscosity, the excess Helmholtz energy and the surface tension.

Concrete pavements subjected to fast evaporation during the first hours after concrete placing are prone to plastic shrinkage cracking. In this paper the mechanisms by which evaporation of water leads to capillary pressure, and finally to shrinkage and cracking, are briefly discussed. In the main part, the paper presents results of a study on the evaluation of three different measurement setups. With two of these setups usually the efficiency of fibres in reducing plastic shrinkage cracking of concrete is assessed in Germany and Austria. The third one is an advanced setup that was developed in collaboration of BAM and Empa. It allows performing measurements of parameters that are important for the evaluation of the cracking risk.

In diesem Beitrag werden Untersuchungsergebnisse vorgestellt, die den Einfluss von Mikrosilica auf die Selbstaustrocknung und das damit verbundene autogene Schwinden der Bindemittelmatrix von Hochleistungsbetonen beschreiben. Die dadurch hervorgerufenen Schadigungsprozesse wurden mit Hilfe von zerstorungsfreien Prufmethoden verfolgt. Dabei zeigte sich, dass eine durch auseren Zwang bedingte Mikrorissbildung durch Schallemissionsanalyse detektiert werden kann.

Thermal curing of Ultra-High Performance Concrete (UHPC) has a strong influence on its mechanical properties. By applying a water vapor saturation pressure additional to the increased temperature the curing conditions are strongly enhanced and lead to a significant improvement of the degree of hydration of the cement paste. Increasing temperature accelerates the formation of crystalline calcium silicate hydrates by dehydrating the cement paste and ends in the formation of gyrolite, truscottite and xonotlite at 200 °C and 15 bars. Thereby the micro structure undergoes an obvious change. Cement paste consists of close networked crystal fibers with dimensions up to 1 μm. By filling cracks and small pores with crystalline C-S-H phases, flaws in the matrix are healed and generate a more homogeneous micro structure. Additionally, autoclaving encourages dissolution processes at quartz grains, which produces a better cohesion between fillers and the fine crystalline cement paste. As a consequence, autoclaving enhances compressive and flexural strength significantly but, compared to simple heat treatment at 1 bar, with very low scatter of the test results.

Thermal curing of Ultra-High Performance Concrete (UHPC) has a significant influence on its mechanical properties. When additionally a water vapour saturation pressure is applied (autoclaving), the curing conditions are strongly enhanced, leading to an improved hydration of cement and secondary cementitious materials. Autoclaved UHPC exhibits a cement paste matrix of close networked C-S-H crystal fibres. Flaws are filled with crystalline reaction products generating a more homogenous micro structure. As a consequence, the mechanical properties of UHPC are improved significantly. The partial reaction of quartz filler grains may contribute by improving the cohesion with the cement paste.

The influence of the mix composition on the early-age autogenous shrinkage of high-strength cement paste with and without silica fume and the resulting crack formation were investigated. The mechanisms of autogenous shrinkage were studied systematically by linking the measured deformations to hydration kinetics and to pore structure data. The time t0 which assigns the transition from the plastic state to a solid structure was determined by analysis of the measured strain rate. It was demonstrated that the autogenous shrinkage correlates reasonably well with the self-desiccation and the thereby expected capillary stresses. The crack formation was detected using acoustic emission (AE) analysis. AE measurements were performed simultaneously on hardening silica fume cement pastes with and without external restraint of deformation. The results showed that the intense autogenous shrinkage during the acceleration period of cement hydration was associated with the begin of micro cracking shortly after t0, irrespective of the existence of external restraint. The cracking was more pronounced in the case of restraint.

The influence of the mix composition on the early-age deformations of the cement paste matrix of high-strength and self-compacting concretes has been investigated. Linear deformation measurements were started prior to setting. Setting (distinction between plastic and stress inducing shrinkage) was determined by analysis of deformation velocity. The measured deformations were linked to the hydration of the binders and to the structural properties of the hardening pastes. The effect of mineral and organic additives on the cement hydration was systematically assessed with isothermal calorimetry and thermogravimetric analysis. Based on hydration data the capillary tension (as the presumed main driving force of autogenous shrinkage) was estimated using pore structure data determined by mercury intrusion porosimetry. From the results conclusions were drawn on the deformation behaviour of the cement pastes.

In this paper a modelling approach is presented to reproduce the mechanical behaviour of sandwich panels via finite element analysis. Two types of panels were investigated in this scope of work. The first sandwich element was a textile reinforced concrete (TRC) panel with cellular lightweight concrete insulation and the second configuration was an ultra-high performances concrete (UHPC) panel with aerated autoclaved concrete insulation. The goal was to obtain a reliable numerical strategy that represents a reasonable compromise in terms of sufficient accuracy of the element characteristics and the computational costs. The results show the possibility of describing the composite action in a full sandwich panel. The achieved modelling approach will later be used for the optimization of TRC and UHPC panels in terms of minimizing the thickness, identifying the number and location of connectors, as well as evaluating varying anchorage systems.

[EN] One promising way to improve the efficiency of borehole heat exchangers (BHEs) in shallow geothermal applications is to enhance the thermal properties of the materials involved in its construction. Early attempts, such as using metal tubes in the 1980s or the utilization of thin-foil hoses, did not succeed in being adopted by the market for diverse reasons (cost, corrosion, fragility, etc...). In parallel, the optimization of pipe size, the use of double-U-tubes, thermally enhanced grout, etc. were able to bring the measure for the BHE efficiency, the borehole thermal resistance, from 0.20 to 0.15 K/(Wm) down to 0.08-0.06 K/(Wm) in the best solutions today. A further improvement cannot be expected without development of new, dedicated materials, combining the versatility of plastic like PE with an increased thermal conductivity that matches the respective properties of the rock and soil. This goal was included in the Strategic Research and Innovation Agenda of the European Technology Platform on Renewable Heating and Cooling in 2013. Within an EU supported project, both BHE pipes and grouting materials have been produced prototypically in small amounts, suitable for the first tests in the intended environment. The present work explains the research pathways envisaged and the resulting sensitivity analysis to highlight the influence of some of the most critical parameters that affect the overall performance of a GSHP system. The results have allowed guiding the real development of more efficient new advanced materials for different scenarios representative of different European regions. Finally the developed materials and their properties are discussed, including a comparative assessment about their compliance with reference material properties as currently seen in the BHE market., This article is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 727583.