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Transport and reconfiguration of moisture in HPC due to unilateral heating

  • Explosive spalling is caused by, among others, the thermohydraulic spalling mechanism. During this process, vaporization, dehydration, moisture-transport and condensation processes interact. As a result, a drying and dehydration zone as well as a saturated zone, known as a moisture clog, are observed inside the unilaterally-heated concrete. The presented research is focused on the experimental investigation of the underlying thermohydraulic processes. To investigate these, a test methodology based on X-ray computed tomography (CT) and nuclear magnetic resonance (NMR) was developed. Thereby, the X-ray CT scans are carried out simultaneously during the application of a defined unilateral-heating regime on a specially-constructed specimen. This miniaturized specimen, equipped with a double-layer casing, reproduces the condition within a planar, unilaterally-heated building component. A preliminary test methodology and the first experimental results were presented at the 5thExplosive spalling is caused by, among others, the thermohydraulic spalling mechanism. During this process, vaporization, dehydration, moisture-transport and condensation processes interact. As a result, a drying and dehydration zone as well as a saturated zone, known as a moisture clog, are observed inside the unilaterally-heated concrete. The presented research is focused on the experimental investigation of the underlying thermohydraulic processes. To investigate these, a test methodology based on X-ray computed tomography (CT) and nuclear magnetic resonance (NMR) was developed. Thereby, the X-ray CT scans are carried out simultaneously during the application of a defined unilateral-heating regime on a specially-constructed specimen. This miniaturized specimen, equipped with a double-layer casing, reproduces the condition within a planar, unilaterally-heated building component. A preliminary test methodology and the first experimental results were presented at the 5th International Workshop on Concrete Spalling in Borås, Sweden (2017). The contribution for the upcoming workshop presents an improved version of this test methodology and new results for a high-performance concrete (HPC) mixture exposed to temperatures up to 500 °C. Regarding the CT measurements, a higher time-resolution of 15 min was achieved and a quantification of the moisture changes was implemented. Due to an increase in signal quality of the NMR measurements, a pore-size specific moisture distribution can now be resolved. This allows to conclude about the moisture reconfiguration between small gel pores and larger interhydrate pores. Additionally, the NMR measurement are no longer limited to first 2.5 cm below the heated surface but a one-dimensional moisture distribution can now be estimated over the whole 10 cm long specimen. The presented results demonstrate that the combination of X-ray CT and NMR measurements enables to image and quantify the thermally-induced moisture transport and reconfiguration from small gel pores up to macro pores. This provides important insights into the thermohydraulic damage mechanism and leads to a better understanding of spalling avoidance strategies, like the addition of polypropylene fibres.zeige mehrzeige weniger

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Autor*innen:Ludwig StelznerORCiD, Frank WeiseORCiD, Tyler OeschORCiD, R. Dlugosch, Bartosz Powierza
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Graue Literatur
Sprache:Deutsch
Titel des übergeordneten Werkes (Deutsch):Proceedings of the 6th International Workshop on Concrete Spalling due to Fire Exposure
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:7 Bauwerkssicherheit
7 Bauwerkssicherheit / 7.1 Baustoffe
8 Zerstörungsfreie Prüfung
8 Zerstörungsfreie Prüfung / 8.5 Röntgenbildgebung
Herausgeber (Institution):The University of Sheffield
Verlagsort:Sheffield
Erste Seite:181
Letzte Seite:190
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurbau
Freie Schlagwörter:HPC; Moisture clog; Moisture transport; NMR; X-ray CT
Themenfelder/Aktivitätsfelder der BAM:Chemie und Prozesstechnik
Infrastruktur
Infrastruktur / Fire Science
Material
Material / Degradation von Werkstoffen
Veranstaltung:6th International Workshop on Concrete Spalling due to fire exposure
Veranstaltungsort:Sheffield, UK
Beginndatum der Veranstaltung:19.09.2019
Enddatum der Veranstaltung:20.09.2019
URL:https://firespallingworkshop2019.group.shef.ac.uk/wp-content/uploads/2019/09/Fire-Spalling-Workshop_Proceedings.pdf
ISBN:978-1-5272-4135-0
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:01.10.2019
Referierte Publikation:Nein
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