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  • 1
    In: Materials, MDPI AG, Vol. 16, No. 3 ( 2023-02-02), p. 1272-
    Abstract: Knowledge of the exact composition of building materials (aggregate, binder, air voids, etc.) is essential for the further development of more resistant and sustainable building materials. In numerous scientific studies, the material behavior of asphalt is tested using mechanical methods. Here, the overall material behavior is determined (bitumen, air voids, aggregate). With the advent of imaging techniques, it is becoming possible to determine the individual constituents separately and perform a more detailed analysis of their location, shape and composition. Three-dimensional and two-dimensional methods are available for this purpose. For this study, two different types of asphalt (porous asphalt and asphalt concrete) were analyzed using 3D X-ray computed tomography and asphalt petrology as 2D methods; the results of both investigations are compared. The objective of this study is to determine whether the 2D method provides suitable results for the microstructural analysis of asphalt samples and how the results differ from those studied by the 3D method. The comparison shows that both methods can be used to analyze voids in asphalt samples. The 2D method provides valuable insight into the distribution of voids in a sample. In addition to the distribution of voids within a 2D section, the 2D method can also be used to make some structural statements about the location and structure of the voids in the 2D plane. The X-ray computed tomography method allows more complex analyses of the pore structure because of the third direction (3D). In addition, the 3D method provides more data, so that the pore structure can be described even more precisely, and the pore size (length, width, height) can be mapped and analyzed with a high degree of accuracy.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2487261-1
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  • 2
    In: Materials, MDPI AG, Vol. 14, No. 24 ( 2021-12-09), p. 7556-
    Abstract: The material behavior of asphalt depends on its composition of aggregate, bitumen, and air voids. Asphalt pavements consist of multiple layers, making the interaction of the materials at the layer boundary important so that any stresses that occur can be relieved. The material behavior at the layer boundary is not yet understood in detail, as further methods of analysis are lacking in addition to mechanical methods. For this reason, the layer boundary of asphalt structures was analyzed using imaging methods. The aim of this research was to find an imaging method that allows a detailed analysis of the bonding zone of asphalt layers. Two different imaging techniques were used for this purpose. One is a 2-D imaging technique (asphalt petrology) and the other is a 3-D imaging technique (high-resolution computed tomography). Image analysis is a widely used technique in materials science that allows to analyze the material behavior and their composition. In this research, attention was paid to the analysis of the position of the bitumen emulsion, because the contained bitumen is supposed to bond the layers together. It was found that the application of 2-D imaging (asphalt petrology) lacked the precision for a detailed analysis of the individual materials at the layer boundary. With high-resolution computed tomography, a detailed view is possible to visualize the individual materials at the layer boundary in 3D. However, it is difficult to differentiate the materials because there are no gradations in the gray values due to the identical densities. However, it is possible to differentiate between the bitumen from the asphalt and from the emulsion if a high-density tracer is added to the bitumen emulsion for the CT studies. The results of the investigations are presented in this article.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2487261-1
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  • 3
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Quality and Reliability Engineering International Vol. 37, No. 2 ( 2021-03), p. 391-408
    In: Quality and Reliability Engineering International, Wiley, Vol. 37, No. 2 ( 2021-03), p. 391-408
    Abstract: Calcium silicate units are versatile and widely used construction materials for edifices. Their production process involves several factors that concern either the mixture of the raw materials or the curing process. The understanding of how raw materials and process variables interact in achieving the compressive strength of the final product enables a cost‐ and energy‐efficient layout of the production process. In this paper, we use mixture‐process experiments to derive a prediction model for compressive strength. We compare computer‐generated D‐optimal designs with different numbers of center points by various criteria and by their prediction variance throughout the design space. In contrast to traditional mixture designs, these designs take additional constraints on the mixture components into account and can include process variables. We review suitable response‐surface models, which combine mixture and process variables. Based on results from 72 experimental runs, a model for the mean compressive strength is built, combining expert knowledge with statistical model‐selection strategies. The resulting model covers not only linear effects of mixture components and process variables but also interactions and quadratic terms. For example, the influence of the lime share on compressive strength differs among the use of various sand mixtures. For desired values of predicted compressive strength, factor settings can thereby be found reducing costs and energy emission.
    Type of Medium: Online Resource
    ISSN: 0748-8017 , 1099-1638
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 50641-2
    detail.hit.zdb_id: 2021089-9
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  • 4
    Online Resource
    Online Resource
    Elsevier BV ; 2023
    In:  Construction and Building Materials Vol. 376 ( 2023-05), p. 131043-
    In: Construction and Building Materials, Elsevier BV, Vol. 376 ( 2023-05), p. 131043-
    Type of Medium: Online Resource
    ISSN: 0950-0618
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 58896-9
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  • 5
    In: Mauerwerk, Wiley, Vol. 13, No. 1 ( 2009-02), p. 46-49
    Abstract: Im Rahmen eines Forschungsprojektes wurde ein neuer Recycling‐Mauerstein entwickelt, dessen Herstellung unter Verwendung von Original‐Mauerwerk‐Abbruchmaterial und unter Einsatz der Kalksandstein‐Technologie erfolgt. Bei den auf diese Weise hergestellten Mauersteinen handelt es sich nicht um Kalksandsteine, sondern um Recycling‐Mauersteine. Die wichtigsten Ergebnisse des Forschungsprojektes sind im folgenden Beitrag zusammengestellt. Der komplette Bericht mit allen Untersuchungsergebnissen ist in [1] wiedergegeben (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    Type of Medium: Online Resource
    ISSN: 1432-3427 , 1437-1022
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2009
    detail.hit.zdb_id: 2151240-1
    detail.hit.zdb_id: 1383256-6
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  • 6
    Online Resource
    Online Resource
    Wiley ; 2018
    In:  Beton- und Stahlbetonbau Vol. 113, No. 8 ( 2018-08), p. 608-613
    In: Beton- und Stahlbetonbau, Wiley, Vol. 113, No. 8 ( 2018-08), p. 608-613
    Abstract: Quartz‐powder free UHPC with limestone‐powder or basalt‐powder In Germany ultra‐high performance concrete is currently being used especially in the field of precast concrete elements. The special properties resulting from a low water/binder ratio of approx. 0.2 and the use of high‐performance superplasticizers and fine particles to increase the packing density. In addition to the use of the reactive silica powder as the finest component, the use of quartz powder is also crucial for the optimum packing density and thus beneath other effects crucial for the particularly high durability and high compressive strength. Since quartz powder is respirable and proven to be carcinogenic, alternatives are urgently sought. Based on an existing UHPC‐mix the quartz powder was substituted by limestone‐ and basalt powder in this study. After the optimization of the fresh concrete properties, the hardened concrete was characterized. The criteria of a UHPC can be met with limestone and basalt powder. In the case of basalt powder further advantages result for the mechanical properties.
    Type of Medium: Online Resource
    ISSN: 0005-9900 , 1437-1006
    URL: Issue
    RVK:
    Language: German
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2151239-5
    detail.hit.zdb_id: 240053-4
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  • 7
    Online Resource
    Online Resource
    Elsevier BV ; 2019
    In:  Materials Today: Proceedings Vol. 15 ( 2019), p. 356-363
    In: Materials Today: Proceedings, Elsevier BV, Vol. 15 ( 2019), p. 356-363
    Type of Medium: Online Resource
    ISSN: 2214-7853
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2019
    detail.hit.zdb_id: 2797693-2
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  • 8
    Online Resource
    Online Resource
    Wiley ; 2023
    In:  ce/papers Vol. 6, No. 6 ( 2023-12), p. 477-483
    In: ce/papers, Wiley, Vol. 6, No. 6 ( 2023-12), p. 477-483
    Abstract: Admixtures play a key role in improving the performance of the cement paste matrix. A more efficient matrix can allow a reduction the binder content while maintaining the same properties. There is currently a lack of knowledge about the spatial distribution of admixtures in situ on binder surfaces which would facilitate the use of admixtures in general in inorganic binder systems. Imaging techniques such as confocal laser scanning microscopy (CLSM) and fluorescence microscopy can be used to study the spatiotemporal adsorption of superplasticizers and plasticizers on binder particles. However, in order to make the admixtures visible using these methods, they must first be coupled to a fluorescent molecule (staining). Different types of superplasticizers and plasticizers, including polycarboxylate ethers (PCE) and lignosulfonate (LS) were stained and tested. It was shown that not only adsorption but also desorption can be observed and that desorption cannot play a relevant role in a binder system. The absence of desorption could be used to observe a real system in permanent preparations, so that the adsorption on individual cement grains could be followed in a time‐dependent manner. The newly developed method provides unprecedented insight into the adsorption of additives.
    Type of Medium: Online Resource
    ISSN: 2509-7075 , 2509-7075
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2894657-1
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  • 9
    In: ce/papers, Wiley, Vol. 6, No. 6 ( 2023-12), p. 1613-1617
    Abstract: Rund 20% der aus den Rohstoffen Kalk, Sand und Wasser hergestellten Kalksandsteine (KS) in KS‐XL‐Formaten werden zur Vorkonfektionierung gesägt. Dabei fallen in den KS‐Werken insgesamt rd. 20.000 t Sägeschlämme pro Jahr an, die derzeit keiner gezielten Verwendung zugeführt werden. Allerdings handelt es sich dabei bereits unter Einsatz von CO2‐intensivem Branntkalk gehärtetes Material, welches als Optimierungszusatz genutzt werden kann. Insgesamt 13 verschiedene Sägeschlämme (SäS) wurden hinsichtlich ihrer Eignung chemisch‐mineralogisch charakterisiert. Anschließend wurden diese zur Reduzierung der Branntkalkdosis für die KS‐Herstellung genutzt. Dazu wurden Versuchsbedingungen und Rezepturen systematisch variiert, wobei die Versuche auf Labor‐, Technikums‐ und Werksebene durchgeführt wurden. Im Optimalfall können bis zu 2 M.‐% des eingesetzten Branntkalks durch SäS substituiert werden, ohne die Eigenschaften der KS negativ zu beeinflussen. In manchen Fällen können Eigenschaften wie Druckfestigkeit und Porosität sogar positiv beeinflusst werden. Durch den vergleichsweise geringen zusätzlichen Aufwand, um die entsprechenden SäS in den Herstellungsprozess einzubinden, können so Produktionskosten und CO2‐Emissionen gesenkt werden.
    Type of Medium: Online Resource
    ISSN: 2509-7075 , 2509-7075
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2894657-1
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  • 10
    In: Diabetologia, Springer Science and Business Media LLC, Vol. 66, No. 7 ( 2023-07), p. 1260-1272
    Type of Medium: Online Resource
    ISSN: 0012-186X , 1432-0428
    RVK:
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 1458993-X
    detail.hit.zdb_id: 1694-9
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