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For several years, optical measuring techniques play an ever increasing role in various areas of construction. Applications ränge from simple laser-based distance measurements up to the use of advanced camera Systems to assess shape changes of components. The advantages of such Systems lie in the ränge of non-contact respectively in non-destructive measurement and in the high required accuracy and reproducibility. The continuous improvement and development of sensors and laser sources also opens constantly new applications and areas of applications. Already established measurement methods and technologies can be further developed and adapted to modern requirements. At BAM it is a laser-based measurement System has been developed that is capable to measure the roughness of component surfaces in equal to already established methods.
Rising temperatures worldwide pose an increasing challenge for safe and healthy living conditions. Particularly inner cities have been affected by these environmental changes because of the materials used to build houses, streets and infrastructure. The most common building material is concrete. It shows a specific heat capacity, while the heat conductivity for Standard concrete is low. Thus, the use of concrete generates a high capacity of heat storage. In addition, extensive soil sealing also contributes to the temperature rise of inner city areas compared to
their surroundings. To mitigate this so-called urban heat island effect, a self-cooling concrete paver was developed. This paver is able to store water. The evaporation of the water at elevated temperatures provides a cooling effect. This paper focuses on determination of this new paver’s capability to cool the surface and the surrounding. The new paver’s cooling Qualities were analysed in a series of laboratory tests. To prove the results outside of laboratory conditions, two fields (12 m × 8 m) with self-cooling and reference pavers were installed in Spain.
This paper presents and discusses the results of the tests. Correlation between reduced surface temperature of the self-cooling concrete pavers and the air temperature is examined.
Properties of alkali-activated mortars with salt aggregate for sealing structures in evaporite rock
(2021)
Concrete structures for sealing of tunnels in the host rock are an essential part of systems for nuclear waste storage. However, concretes based on blended cements or magnesium oxychloride cements, which are commonly considered for this application, can deteriorate severely due to a significant heat of hydration and associated deformation and cracking. Alkali-activated materials (AAMs) offer a potential solution to this problem because of their low heat release during hardening. To explore their suitability for the construction of sealing structures in evaporite rock, various AAMs with salt aggregate were studied regarding fresh properties, heat release, mechanical properties and microstructure. The heat of reaction of the AAMs was up to 55% lower than that of a blended cement designed for sealing structures, indicating significant benefits for the intended application. Other relevant properties such as mechanical strength and permeability depended strongly on the mix-design of the AAMs and curing conditions.
In the last several decades, the rural exodus has led to an increasing number of inhabitants in the urban areas. The increased building and infrastructural construction caused the transformation of the landscape and to an increased land sealing in these areas. Consequently, the increased land sealing influences the air temperatures in the cities, since houses, streets and squares heat up continuously. As a result, the city and metropolitan areas became significantly warmer than their surroundings - the effect is known as Urban Heat Island (UHI). These changes have a negative impact for the quality of life. To deal with the negative effects of UHI, a high level of technical and financial effort is necessary. The costs caused by the UHI effects are in the range of several billion US dollars worldwide per year. The recent studies on UHI showed that the established methods like parks and green spaces or bright coatings for roof areas will soon not be able to effectively cope with the UHI effect in urban areas. Therefore there is a need for additional methods to mitigate UHI effect in the cities. The streets, sidewalks and squares represent approximately 30% to 40% of the inner cities areas. If these areas are designed functionally, they can have a significant impact on the UHI. This contribution focuses on development of a concrete paving stone with self-cooling properties. For the cooling effect the evaporative cooling is used. The paving stone is able to store large quantities of water and deliver during appropriate environmental conditions. This paper deals with the results of the long-term experiments on the test-fields under different climatic conditions. To interpret the test-field-results, laboratory tests were carried out as well. The paper presents and discuss the obtained results, and points out the difficulties occurred.
Die Oberflächenrauheit eines Bauteils ist eine wichtige Kenngröße für zahlreiche seiner Eigenschaften. Der im Bauwesen übliche Rauheitsparameter ist die Rautiefe Rt bzw. MTD, die durch volumetrische Verfahren (Sandflächenverfahren) ermittelt wird und in zahlreichen Normen Verwendung findet. Laserbasierte Verfahren müssen deshalb eine Umrechnung der aus Oberflächenprofilen gewonnenen Informationen in Rt bzw. MTD ermöglichen. Hierzu wird i.A. ein empirischer Zusammenhang zwischen Parametern zur Beschreibung des Profils und der Rautiefe der entsprechenden Oberfläche verwendet. Der Aufsatz stellt verschiedene Rauheitsdefinitionen vor und vergleicht sie miteinander. Es wird ferner gezeigt, dass die nach verschiedenen Prüfvorschriften ermittelten Rautiefen voneinander abweichen. Das Vorgehen bei der Ermittlung des Zusammenhangs zwischen Profilparametern und Rautiefen nach einem volumetrischen Verfahren wird demonstriert und der Stand der laufenden Entwicklung eines Prüfgeräts auf Basis eines Linienlasers vorgestellt.