Beton- und Stahlbetonbau最新文献

Im April 2025 wurde in der HafenCity das Westfield Hamburg-Überseequartier eröffnet – zeitweise Hamburgs größte Baustelle. Die Realisierung des Quartiers mit insgesamt 419.000 m² BGF stellte Planer und Ausführende vor vielfältige Herausforderungen. So mussten u. a. tiefe Baugruben in unmittelbarer Nähe zur Elbe geplant werden – unter Berücksichtigung eines im Betrieb befindlichen U-Bahn-Haltestellenbauwerks, das mitten durch das Baufeld verläuft. Die Planung der Untergeschosse und aller 14 aufgehenden Gebäude erfolgte mit der BIM-Methodik. Über die Ingenieurbauwerke wurde bereits 2024 berichtet; in diesem Heft liegt der Fokus auf den Tragwerken der Gebäude. Das Bild zeigt den Rohbau der drei Untergeschosse im südlich der U-Bahn gelegenen Bauabschnitt im Juni 2020. Siehe Bericht auf den Seiten 537–545. (Bild: WTM Engineers)

The ageing exponent for the durability design of concrete exposed to chlorides part 1: Basics and determination of the ageing exponent

For the concept of durability design of concrete under chloride exposure, engineering models are used to describe the diffusion-based chloride transport. The binder-dependent ageing exponent of the concrete is one of the decisive parameters. It describes the time-dependent decrease in the apparent chloride diffusion coefficient, and thus, the long-term development of the material resistance of concrete. This article first deals with the prediction model for describing the chloride ingress into concrete in the combination with the explanation of the ageing exponent. The focus is on the description of the various methods available in the literature for determining the ageing exponent. These methods are based on laboratory and/or on-site investigations. The choice of method has a significant influence on the ageing exponent and thus on the durability design of the concrete. In addition, the ageing exponent is a decisive parameter for classification when implementing the concept of exposure resistance classes (ERC) in accordance with prEN 1992-1-1. The two-part publication is intended to contribute to the uniform evaluation of the chloride penetration resistance of concrete. The first part deals with the principles and procedures for determining the ageing exponent, while the second part explains the influences on the ageing exponent using calculation examples.

The ageing exponent for the durability design of concrete exposed to chlorides part 2: Calculation examples and influences on the ageing exponent

In this second part of the article, the practical applicability of various methods for determining the ageing exponent for the durability design of concrete under chloride exposure is considered. Calculation examples are shown and evaluated on the basis of real laboratory and structural data. The focus is on the methodical evaluation of chloride profiles and the influences that can result from the determination of apparent chloride diffusion coefficients. This includes in particular the consideration of the convection zone. It is shown that both, the available and thus applicable data basis, as well as the selected evaluation methodology of the chloride profiles have a considerable influence on the determined ageing exponents. In this context, the possibilities and limitations of the methods presented are explained and discussed. The results achieved illustrate the need to formulate a standardized, transparent methodology for determining the ageing exponents of concrete, especially with regard to new cements and binders.