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  • 1
    Online Resource
    Online Resource
    Czech Technical University in Prague - Central Library ; 2022
    In:  Acta Polytechnica CTU Proceedings Vol. 33 ( 2022-03-03), p. 160-167
    In: Acta Polytechnica CTU Proceedings, Czech Technical University in Prague - Central Library, Vol. 33 ( 2022-03-03), p. 160-167
    Abstract: Concrete structures without sufficient durability can be damaged by sulfates in groundwater and from surrounding rock layers. To evaluate the performance of a concrete mixture, precise and performance-oriented test methods are a must. Therefore, a new a performance oriented concrete test procedure based on tensile strength measurements was developed considering experiences reported in international literature and recommendations of state-of-the-art reports. A vast parameter study with approx. 3850 tensile tests on ASTM briquets, 1900 flexural tensile tests on standard prisms and 2100 expansion tests on mortar flat prisms of different ages and with different storage conditions was statistically assessed. Based on the results a performance-oriented test method could be defined which considers not only the chemical, but also the physical resistance of a concrete against sulfate attack. The method was verified by 23 concretes with different cements or cement fly ash combinations and additional field tests. It could clearly be demonstrated that the results represent the performance of a practical concrete in case of sulfate attack. Furthermore, it leads much faster to an evaluation of the sulfate resistance compared to the most other practical oriented methods.
    Type of Medium: Online Resource
    ISSN: 2336-5382
    Language: Unknown
    Publisher: Czech Technical University in Prague - Central Library
    Publication Date: 2022
    detail.hit.zdb_id: 2868262-2
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  • 2
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2021
    In:  Helgoland Marine Research Vol. 75, No. 1 ( 2021-12)
    In: Helgoland Marine Research, Springer Science and Business Media LLC, Vol. 75, No. 1 ( 2021-12)
    Abstract: Concrete is a widely used building material in coastal constructions worldwide. However, limited natural resources used in the production process, as well as high CO 2 -emission due to the calcination process of limestone and the thermal energy demand for Portland cement clinker production, raise the demand for alternative constituents. Alternative mixture types should be environmentally friendly and, at best, mimic natural hard substrates. Here five different concrete mixtures, containing different cements (Portland cement and blast furnace cements) and aggregates (sand, gravel, iron ore and metallurgical slags) were made. Three replicate cubes (15 × 15 × 15 cm) of each type were then deployed in a German deep-water Port, the JadeWeserPort, to study benthic community establishment after one year. Results are compared to a similar experiment conducted in a natural hard ground environment (Helgoland Island, Germany). Results indicate marked differences in settled communities in the Port site compared to natural environments. At the Port site community composition did not differ with the concrete mixtures. Surface orientation of the cubes (front/top/back) revealed significant differences in species abundances and compositions. Cubes hold more neobiota in the Port site than in natural hard ground environments. Implications for the usage of new concrete mixtures are discussed.
    Type of Medium: Online Resource
    ISSN: 1438-387X , 1438-3888
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 3475-7
    detail.hit.zdb_id: 1495261-0
    detail.hit.zdb_id: 572898-8
    detail.hit.zdb_id: 1499108-1
    SSG: 12
    SSG: 14
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  • 3
    In: Marine Environmental Research, Elsevier BV, Vol. 161 ( 2020-10), p. 105081-
    Type of Medium: Online Resource
    ISSN: 0141-1136
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 437280-3
    detail.hit.zdb_id: 1502505-6
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Czech Technical University in Prague - Central Library ; 2022
    In:  Acta Polytechnica CTU Proceedings Vol. 33 ( 2022-03-03), p. 238-244
    In: Acta Polytechnica CTU Proceedings, Czech Technical University in Prague - Central Library, Vol. 33 ( 2022-03-03), p. 238-244
    Abstract: Concrete is widely used in constructions such as industrial floors or airducts in steel- and casting industry where it is often exposed to long-term or cyclic elevated temperatures. For these applications, thermal stability of concrete is of vital importance. The strength reduction dueto elevated temperatures depends on the temperature level and concrete composition. In this study, the effects of blast-furnace slag cement (CEM III/A) and basaltic aggregates were investigated at temperatures 250◦C to 700 ◦C in comparison to conventional Portland cement (CEM I) containing quarzitic aggregates. The concretes were cyclically exposed to high temperatures. Special attention was paid to mass loss, residual compressive and residual flexural strength depending on type of cement and aggregate as well as the number of thermal cycles. Mass loss and strength loss increased with increasing maximum temperature level, as expected. It was generally observed that concretes containing CEM III/A displayed significantly higher residual mechanical properties for almost all temperature levels. Concretes containing a combination of CEM III/Awith basaltic aggregates showed significantly higher stability at elevated temperatures compared to other concrete mixtures. It is further shown that apart from the maximum temperature the number of thermal cycles is important for the residual mechanical properties.
    Type of Medium: Online Resource
    ISSN: 2336-5382
    Language: Unknown
    Publisher: Czech Technical University in Prague - Central Library
    Publication Date: 2022
    detail.hit.zdb_id: 2868262-2
    Location Call Number Limitation Availability
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