Zürich, Switzerland
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Fang X.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Garcia A.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Garcia A.,University of Nottingham | Partl M.N.,Empa - Swiss Federal Laboratories for Materials Science and Technology | And 3 more authors.
Asphalt Pavements - Proceedings of the International Conference on Asphalt Pavements, ISAP 2014 | Year: 2014

Cement Asphalt Emulsion Composites (CAEC) are mixtures of bitumen emulsion, cement, water and aggregates that harden at ambient temperature. They are mixed at ambient temperature and harden due to breaking of the emulsion, water evaporation and cement hydration. Potential advantages of CAEC are lower temperature susceptibility than asphalt concrete and higher flexibility than cement concrete. To quantify the effects of cement hydration on the mechanical properties of CAEC, two different emulsions (cationic and anionic) mixed with either 0%, 3% and 6% Ordinary Portland Cement (OPC) by mass of dry aggregates were studied by isothermal calorimetry and Marshall tests. By monitoring the mass of the specimens and estimating the amount of water bound by the cement, the water content was calculated. This study shows that bitumen emulsion has no significant effect on the degree of cement hydration. Cement hydration, however, significantly contributes to the hardening of CAEC. Moreover, a higher amount of cement added to the mixture results in a higher amount of bound, adsorbed and capillary water in the CAEC. © 2014 Taylor & Francis Group, London.

Lohaus L.,Institute for Building Materials | Lindschulte N.,Institute for Building Materials | Anders S.,Bilfinger Berger AG
European Wind Energy Conference and Exhibition 2010, EWEC 2010 | Year: 2010

Grouted Joints are typical means of connecting the supporting structure with the foundation piles of Offshore Wind Energy Converters (OWECs). The resulting gap of two steel pipes with different diameters is filled using a mineral-bound, high strength grout. Because of the special offshore conditions the grout material needs a high reliability and robustness against segregation for the pumping process. Up to now high performance concrete can be used with compressive strength exceeding 100 N/mm2. Because of the brittleness and risk of cracking in case of high performance grout material, discussions have come up in Germany whether to use steel fibres due to their crack-bridging effects. In this paper the opportunities and risks of steel fibres in Grouted Joints are described regarding to their effects on the fresh and hardenend concrete properties as well as the load-deformation behaviour of the construction. It is necessary to balance needs for the controllability of the filling process and the risk of cracking of hardened grout materials with and without fibre reinforcement. To determine the influence of steel fibres on the workability, slump flow tests with and without blocking effects were made. Currently, it is not recommended to use steel fibres for structural purposes. High doses of steel fibres, which produce an identifiable improvement of the load bearing behaviour result in critical problems for the filling process.

Orsolini P.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Orsolini P.,ETH Zurich | Michen B.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Michen B.,Institute for Building Materials | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Nanofibrillated cellulose (NFC) is a natural fibrous material that can be readily processed into membranes. NFC membranes for fluid separation work in aqueous medium, thus in their swollen state. The present study is devoted to a critical investigation of porosity, pore volume, specific surface area, and pore size distribution of dry and wet NFC nanopapers, also known as membranes, with various established techniques, such as electron microscopy, helium pycnometry, mercury intrusion, gas adsorption (N2 and Kr), and thermoporometry. Although these techniques can be successfully applied to inorganic materials (e.g., mesoporous silica), it is necessary to appraise them for organic and hydrophilic products such as NFC membranes. This is due to different phenomena occurring at the materials interfaces with the probing fluids. Mercury intrusion and gas adsorption are often used for the characterization of porosity-related properties; nevertheless, both techniques characterize materials in the dry state. In parallel, thermoporometry was employed to monitor the structure changes upon swelling, and a water permeance test was run to show the accessibility of the membranes to fluids. For the first time, the methods were systematically screened, and we highlighted the need of uniform sample treatments prior to the measurements (i.e., sample cutting and outgassing protocols) in order to harmonize results from the literature. The need for revising the applicability range of mercury intrusion and the inappropriateness of nitrogen adsorption were pointed out. We finally present a table for selecting the most appropriate method to determine a desired property and propose guidelines for results interpretation from which future users could profit. © 2015 American Chemical Society.

Schneider C.M.,Institute for Building Materials | Schneider C.M.,Massachusetts Institute of Technology | Kesselring T.A.,Institute for Building Materials | Andrade J.S.,Federal University of Ceará | And 2 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The self-similarity of complex networks is typically investigated through computational algorithms, the primary task of which is to cover the structure with a minimal number of boxes. Here we introduce a box-covering algorithm that outperforms previous ones in most cases. For the two benchmark cases tested, namely, the E. coli and the World Wide Web (WWW) networks, our results show that the improvement can be rather substantial, reaching up to 15% in the case of the WWW network. © 2012 American Physical Society.

Baradit E.,University of Bío Bío | Baradit E.,Institute for Building Materials | Niemz P.,University of Bío Bío | Niemz P.,Institute for Building Materials
Wood Research | Year: 2012

The aim of this work is to determine the Young's modules and shear modules of elasticity of four native Chilean hardwoods (Tepa (Laureliopsis philipianà), Olivillo (Aextoxkon punctatum), Laurel (Laurelia sempervirens) and Lenga (Nothofagus pumilio) and two Chilean softwoods (Alerce (Fitzroya cupressoides) and Manio (Podocarpus nubigend)) using ultrasound techniques. Longitudinal and transversal waves were used to determine the three MOE in the longitudinal, radial and transversal directions and also the shear modules 0 LR, GLT and G RT\ The results show higher anisotropy behavior for the tested hardwoods in relation to softwoods. This is in contrast to most European species, which have a higher anisotropy for softwood than for hardwood.

Baradit E.,Universided Del Bio Bio | Keunecke D.,Institute For Building Materials | Schnider T.,Institute For Building Materials | Niemz P.,Institute For Building Materials | Zurich E.,Institute For Building Materials
Wood Research | Year: 2012

Comprehensive datasets of the elastic constants are available for only a few European wood Species, especially spruce. The goal of this study, therefore, was to provide Young's and shear moduli for the principal directions and planes for further selected extraneous species to extend the currently existing datasets. For this purpose, a dynamic technique was chosen: The moduli were estimated on the basis of sound velocity and density measurements. The collected data may be helpful for specialists in the relevant research and practical fields, particularly when stresses and strains of structural elements have to be calculated using modeling approaches.

Wittel F.K.,Institute for Building Materials | Kovacs K.,Institute for Building Materials | Herrmann H.J.,Institute for Building Materials
18th European Conference on Fracture: Fracture of Materials and Structures from Micro to Macro Scale | Year: 2010

Discrete Element Methods are characterized by dynamic multi-body interaction. Hence its applicability for the study of dynamic crack propagation is obvious. However, trying to do so very soon leads to the dilemma, that models with a good spatial resolution of the crack process zone, are simply too small to simulate crack propagation at a constant crack velocity vc. Using larger models unfortunately leads to a worse prediction of the damage process since the computer power is a fixed property. Most properties of dynamic crack propagation depend on the relation of crack velocity to the Rayleigh wave speed cR. We propose a model approach, where damaged parts of the model are removed and new, pre-stressed parts are added to the intact side of the system in crack propagation direction. This way the system size can be kept constant as the simulation proceeds, basically allowing for an infinitely long crack that can grow under constant conditions. Using a model that consists of particles connected by a network of Timoshenko truss-beam elements, we simulate crack propagation in two dimensions at various velocities and amounts of topological disorder. Among other, we study the dependence of morphological characteristics like crack branch geometries, crack roughness and velocity oscillations on the average velocity and disorder.

Sonderegger W.,Institute for Building Materials | Hering S.,Institute for Building Materials | Mannes D.,Paul Scherrer Institute | Vontobel P.,Paul Scherrer Institute | And 2 more authors.
European Journal of Wood and Wood Products | Year: 2010

Diffusion processes into multilayered samples of Norway spruce (Picea abies [L.] Karst.) exposed to a differentiating climate (dry side/wet side) were determined and quantified by means of neutron imaging (NI). The experiments were carried out at the neutron imaging facility NEUTRA at the Paul Scherrer Institute (PSI) in Villigen (Switzerland). With NI the influence of different adhesives (polyvinyl acetate (PVAc), urea formaldehyde resin (UF), epoxy resin (EP), one-component polyurethane (1C PUR)) on the diffusion process could be determined by varying the layer number and the thickness of adhesive joints of the samples. Thereby, neutron transmission images were used to measure time dependent water profiles in the diffusion direction. Using Fick's second law, diffusion coefficients for radial and tangential water transport in spruce wood and in the adhesive joints were calculated depending on moisture content (MC). It was found that the diffusion coefficients of the adhesives (1C PUR, EP at high MC) were up to three orders of magnitude lower than those of spruce wood. PVAc and UF had a smaller barrier effect compared to wood, which in contrast to 1C PUR and EP, clearly depends on the MC. © The Author(s) 2010.

PubMed | Institute for Building Materials
Type: Journal Article | Journal: Physical review. E, Statistical, nonlinear, and soft matter physics | Year: 2012

The self-similarity of complex networks is typically investigated through computational algorithms, the primary task of which is to cover the structure with a minimal number of boxes. Here we introduce a box-covering algorithm that outperforms previous ones in most cases. For the two benchmark cases tested, namely, the E. coli and the World Wide Web (WWW) networks, our results show that the improvement can be rather substantial, reaching up to 15% in the case of the WWW network.

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