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In terms of sustainability and durability, performance-based design is becoming increasingly important for the quality assessment of concrete structures. Up to now, prescriptive approaches for concrete composition and processing and the determination of concrete strength on cast samples have primarily been used as quality assurance. As this does not take into account the quality and pore structure of the as-built concrete cover, which has a significant influence on durability as a protective zone against penetrating media, the conventional approach to quality control is not representative for this zone. In particular, the permeability of the concrete cover, which is largely dependent on the pore structure, is responsible for the ability of aggressive substances from the environment to ingress into the concrete and, depending on its quality, determines damage processes in the reinforced concrete, such as carbonation. For this reason, investigations to gas permeability on real structures are presented here, which include the possibilities and limitations of measuring and evaluating gas permeability as a durability indicator. Long-term observation was carried out on concrete walls of a motorway construction site, from a young concrete age of 14 days to a higher age of max. 800 days, in order to determine changes in the material structure of the surface area and to analyse their influence on the gas permeability. The concrete walls were treated in advance during hydration up to an age of 7 days with different curing times and types in order to simulate good, medium and poor concrete surfaces. Clear differences in the quality of the concrete cover could already be determined by means of gas permeability. The influence of the surface structure, the effect of the environment and the long-term development of the concrete structure on the permeability are also addressed in this work. [ABSTRACT FROM AUTHOR]

Enhancing safety whilst saving energy in tunnels due to an optimised choice of road surface materials The durability and longevity of concrete pavements is well known everywhere. Due to these characteristics the overhaul and maintenance requirements, provided the major construction and production principles are respected, are sharply reduced. This results in a prevention of transport disruptions respectively traffic jams and their subsequent costs. However, there are many more positive characteristics of concrete, which become more and more effective during the entire operating life of concrete surfaces, which are widely unknown. Among other things, concrete pavements can reduce the fuel consumption of lorries (resulting in a reduction of CO2 emission), due to non‐deformable pavements. Furthermore hardened concrete is able to absorb and store CO2 and there are advantages caused by the bright surface of the material. The Smart Minerals GmbH examines the aspect of brightness of concrete for the road surface of tunnels in the course of a research project. Due to the good photometric characteristics of concrete and the resulting higher brightness of the pavement, the road users have a subjective higher sense of safety and the bright surface of concrete causes a reduction of energy‐consumption for lighting. To ensure the required brightness of the pavement, concrete surfaces need much less powerful light sources. Therefore it is theoretically possible to reduce the power of the light source, compared to the asphalt surface, to an extent of two thirds. [ABSTRACT FROM AUTHOR]

Ever more stringent requirements have been specified in recent years for the surfaces of tunnel inner linings with regard to surface porosity (with influence on the ease of cleaning) and lightness. These requirements are normally fulfilled by filling and applying tunnel paint. Recently there have been many cases of damage to paint or coating systems, sometimes only a few weeks after opening for traffic. This often includes the separation of the coating. This flaking leads to increased dirt adhesion and thus to a reduction of lightness and irritation to the field of view of the drivers. The refurbishment work, which is often necessary, leads to traffic obstruction like hold-ups and diversions. For this reason, the durability of the surface is of great significance, and innovative solutions are also being investigated in the field of concrete technology. The following article presents an alternative and durable method of fulfilling all the requirements placed on the surface of the tunnel inner lining. In den vergangenen Jahren wurden immer höhere Anforderungen an die Oberflächen von Tunnelinnenschalen betreffend Oberflächenporosität (Einfluss auf Reinigungsfähigkeit) und Helligkeit gestellt. Zur Erfüllung dieser Anforderungen werden meist Tunnelanstriche nach vorheriger Spachtelung verwendet. In letzter Zeit traten jedoch vermehrt Schäden an Anstrichsystemen auf, teilweise schon wenige Wochen nach Verkehrsfreigabe. Hierbei kommt es oftmals zu einem Ablösen der Anstrichschicht. Diese Ablöseerscheinungen führen aufgrund einer verstärkten Schmutzablagerung zu einer Reduktion der Helligkeit und zu Irritationen des Blickfelds der Verkehrsteilnehmer. Die oftmals erforderlichen Instandsetzungsarbeiten am Beschichtungssystem führen zu Verkehrsbehinderungen wie Staus und Umleitungen. Aus diesen Gründen ist die Beständigkeit der Oberfläche von großer Bedeutung, und innovative Lösungswege werden auch im Bereich der Betontechnologie erprobt. Im nachstehenden Beitrag wird eine alternative dauerhafte Methode vorgestellt, die alle Anforderungen an die Oberfläche der Tunnelinnenschale erfüllt. [ABSTRACT FROM AUTHOR]