Leipzig, Germany
Leipzig, Germany

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Fessel D.,MFPA Leipzig | Simon P.,MFPA Leipzig | Guder T.,MFPA Leipzig | Dehn F.,MFPA Leipzig
Beton- und Stahlbetonbau | Year: 2016

Thermal conductivity of steel fibre reinforced – a theoretical view. With respect to fire design of reinforced and prestressed concrete structures the thermal conductivity λc is one of the important input variables. In case of an addition of steel fibres, statements are contradictory about how these affect the thermal conductivity, and thus, the fire resistance. Against this background, literature data was sighted and completed by systematically theoretical considerations and an computer-based evaluation method. On the basis of theoretical considerations for the thermal resistance of concrete, as well as on the numeric model, in general it can be concluded that, for an in practice frequently used fibre dosage of 1 Vol.-%, the lower and upper curves for the thermal conductivity given in DIN EN 1992-1-2:2010 can be applied for normal- and high-strength concretes. However, for other types of concrete which specifically differ from normal- and high-strength concrete in density, kind, size and distribution of pores as well as in physical and chemical water binding capacity separate observations should be made. Copyright © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin

There are not only the standardised joint seal systems that have proven their worth in sealing joints in concrete constructions impermeable to water for many years. Increasingly, there are alternative systems available, although they require a general building supervisory test certificate as usability documentation. The article below provides a cross-section of the basic types of applications, the particular characteristics of specific product groups, any constraints to be taken into consideration and a classification of the unregulated joint seal in terms of building law. Copyright © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Self-healing behaviour of separating cracks in reinforced concrete structures under the influence of agricultural liquids In the context of a Federal States program "Water, Soil, Waste" financially supported research project, the percolation behaviour of agricultural liquids in cracks was investigated in order to derive conclusive statements how and to which extent self-healing processes can be proven for the aforementioned fluids and which crack widths are calculatory set. Copyright © 2014 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

External thermal composite systems with rendering (ETICS) for use on exterior walls in timber frame constructions are regulated nationally through general building inspectorate approvals. In the course of issuing the approval, the permanently effective weather protection of the timber construction must be proven by the external thermal composite system. This can be carried out on the test bench for walls by measuring the timber moisture contents as well as temperatures and rel. humidities in various areas of the construction with a hygrothermal load pursuant to ETAG 004. Manufacturers of ETICS strive to optimise the time and costs of such tests by only testing the most unfavourable combination of renderings and insulating materials from the wide variety that are available. The decision about the most unfavourable variant is usually taken on the basis of only a few criteria such as the water vapour permeability of the rendering. However, hygrothermal simulations have shown that if various marginal conditions are taken into account, the most unfavourable variant is not always as expected. The article shows by way of example how and under which conditions simulation calculations lead to a more reliable estimate of the hygrothermal behaviour of the different variants of a wall construction. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Rudolph M.,MFPA Leipzig | Hornig U.,MFPA Leipzig
Beton- und Stahlbetonbau | Year: 2010

This article deals with possibilities to seal concrete structures by other products than those authorized by the DAfStb. Among those products are grout injection gels which have several favourable properties which allow the user to seal even those structures where conventional methods might fail. Particularly for acrylate gel there is already a wide range of experience. This article describes the main properties of the materials, standard boundary conditions and the resulting types of sealing: curtain grouting, injections into the structural components or joints between structural elements, in cracks and a mixture of the methods mentioned above. The focus is set on curtain grouting which differs significantly from common grouting to repair cracks and defects. The usage of curtain grouting is limited. A method is described to recognize those limitations. One possibility could be to perform test injections at the original site using water instead of the gel. Apart from technical basics and practical limitations the requirements made by the authorities are characterized. © 2010 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG.

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