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Einfluss der Porosität von Beton auf den Ablauf einer schädigenden Alkali-Kieselsäure-Reaktion

  • This thesis deals with the question of how the porosity of concrete influences the process of a damaging alkali-silica-reaction (“ASR”). In particular, it is examined whether the use of slip form pavers and the reduced porosity resulting from this use have an effect on the process of a damaging ASR. Since the 1980s slip form pavers have been used, which modifies the structure of concrete. However, these modifications have not yet been taken into consideration in the relevant technical guidelines. The use of slip form pavers instead of conventional concrete pavers results in a denser structure. Due to the denser structure the ductility and the porosity of the concrete decrease. Thus it is more difficult for the tensile stress to be reduced. Moreover, the space for the ASR gel to expand is reduced. These consequences promote the ASR. By contrast, the permeability of the concrete is lower. Hence, the penetration of external alkalis is reduced and the diffusion of the alkalis to theThis thesis deals with the question of how the porosity of concrete influences the process of a damaging alkali-silica-reaction (“ASR”). In particular, it is examined whether the use of slip form pavers and the reduced porosity resulting from this use have an effect on the process of a damaging ASR. Since the 1980s slip form pavers have been used, which modifies the structure of concrete. However, these modifications have not yet been taken into consideration in the relevant technical guidelines. The use of slip form pavers instead of conventional concrete pavers results in a denser structure. Due to the denser structure the ductility and the porosity of the concrete decrease. Thus it is more difficult for the tensile stress to be reduced. Moreover, the space for the ASR gel to expand is reduced. These consequences promote the ASR. By contrast, the permeability of the concrete is lower. Hence, the penetration of external alkalis is reduced and the diffusion of the alkalis to the potentially reactive aggregate slowed down. Against this background the question arises whether the use of slip form pavers and the reduced porosity of the concrete increase the risk of a damaging ASR. An innovative non-destructive testing methodology is applied to answer this question. Based on variations of the porosity it is examined which damage parameters influence the process and intensity of a damaging ASR. The damaging parameters taken into consideration are the mechanical properties of the concrete, the expansion space and the transport processes within the concrete. In order to determine the influence of the relevant damaging parameters two categories of tests are conducted: one category is based on a high internal potential for damages due to ASR, the other one on a high external potential. In both cases alkali-reactive slow/late aggregates are tested. The different porosities of the concrete mainly result from a variation of the w/c-ratio. In case of a high internal potential for ASR-damages the mechanical properties and the expansion space play the most important role. Furthermore; the influence of an air-entraining agent on the process of a damaging ASR is taken into account. The high internal potential for ASR-damages is provoked by the use of cement with a high amount of alkalises for the production of the concrete samples. These samples are stored in the 40 °C fog chamber storage and the 60 °C concrete prisms test. On the one hand the expansion and the change in mass as well as the eigenfrequency are measured discontinuously in the conventional way. On the other hand the innovative testing methodology applied to these ASR-provoked stored concrete samples serves to continuously measure the expansion and the hardening as well as crack formation processes. This methodology comprises a determination of the ultrasonic velocity and of acoustic emissions as well as 3-dimensional micro X-ray computed tomography (μ-3D-CT). The high external potential for ASR-damages is provoked by the cyclic climate storage, designed by FIB. The analysis of these concretes focuses on transportation processes.zeige mehrzeige weniger

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Metadaten
Autoren/innen:Katja Voland
Dokumenttyp:Dissertation
Veröffentlichungsform:Eigenverlag BAM
Schriftenreihe (Bandnummer):BAM Dissertationsreihe (147)
Sprache:Deutsch
Jahr der Erstveröffentlichung:2016
Organisationseinheit der BAM:7 Bauwerkssicherheit
7 Bauwerkssicherheit / 7.1 Baustoffe
Veröffentlichende Institution:Bundesanstalt für Materialforschung und -prüfung (BAM)
Titel verleihende Institution:Bauhaus-Universität Weimar, Fakultät Bauingenieurwesen
Gutachter/innen:Jochen Stark, Birgit Meng, Rolf Breitenbücher
Datum der Abschlussprüfung:10.12.2015
Verlag:Bundesanstalt für Materialforschung und -prüfung (BAM)
Verlagsort:Berlin
Jahrgang/Band:147
Erste Seite:1
Letzte Seite:385
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurbau
Freie Schlagwörter:Alkali-Kieselsäure-Reaktion; Laser-Induced Breakdown Spectroscopy (LIBS); Porosität; Schallemissionsanalyse; µ-3D Computertomografie
Themenfelder/Aktivitätsfelder der BAM:Infrastruktur
Infrastruktur / Sicherheit und Lebensdauer von Bauwerken
URN:urn:nbn:de:kobv:b43-363551
ISSN:1613-4249
ISBN:978-3-9817853-0-2
Verfügbarkeit des Volltexts:Volltext-PDF für die Öffentlichkeit verfügbar ("Open Access")
Lizenz (Deutsch):License LogoCreative Commons - Namensnennung-Nicht kommerziell-Keine Bearbeitung
Datum der Freischaltung:06.06.2016
Referierte Publikation:Nein