Salt-frost Attack on Concrete - New Findings regarding the Damage Mechanism

  • The reduction of the cement clinker content is an important prerequisite for the improvement of the CO2-footprint of concrete. Nevertheless, the durability of such concretes must be sufficient to guarantee a satisfactory service life of structures. Salt frost scaling resistance is a critical factor in this regard, as it is often diminished at increased clinker substitution rates. Furthermore, onlyThe reduction of the cement clinker content is an important prerequisite for the improvement of the CO2-footprint of concrete. Nevertheless, the durability of such concretes must be sufficient to guarantee a satisfactory service life of structures. Salt frost scaling resistance is a critical factor in this regard, as it is often diminished at increased clinker substitution rates. Furthermore, only insufficient long-term experience for such concretes exists. A high salt frost scaling resistance thus cannot be achieved by applying only descriptive criteria, such as the concrete composition. It is therefore to be expected, that in the long term a performance based service life prediction will replace the descriptive concept. To achieve the important goal of clinker reduction for concretes also in cold and temperate climates it is important to understand the underlying mechanisms for salt frost scaling. However, conflicting damage theories dominate the current State of the Art. It was consequently derived as the goal of this thesis to evaluate existing damage theories and to examine them experimentally. It was found that only two theories have the potential to describe the salt frost attack satisfactorily – the glue spall theory and the cryogenic suction theory. The glue spall theory attributes the surface scaling to the interaction of an external ice layer with the concrete surface. Only when moderate amounts of deicing salt are present in the test solution the resulting mechanical properties of the ice can cause scaling. However, the results in this thesis indicate that severe scaling also occurs at deicing salt levels, at which the ice is much too soft to damage concrete. Thus, the inability of the glue spall theory to account for all aspects of salt frost scaling was shown. The cryogenic suction theory is based on the eutectic behavior of salt solutions, which consist of two phases – water ice and liquid brine – between the freezing point and the eutectic temperature. The liquid brine acts as an additional moisture reservoir, which facilitates the growth of ice lenses in the surface layer of the concrete. The experiments in this thesis confirmed, that the ice formation in hardened cement paste increases due to the suction of brine at sub-zero temperatures. The extent of additional ice formation was influenced mainly by the porosity and by the chloride binding capacity of the hardened cement paste. Consequently, the cryogenic suction theory plausibly describes the actual generation of scaling, but it has to be expanded by some crucial aspects to represent the salt frost scaling attack completely. The most important aspect is the intensive saturation process, which is ascribed to the so-called micro ice lens pump. Therefore a combined damage theory was proposed, which considers multiple saturation processes. Important aspects of this combined theory were confirmed experimentally. As a result, the combined damage theory constitutes a good basis to understand the salt frost scaling attack on concrete on a fundamental level. Furthermore, a new approach was identified, to account for the reduced salt frost scaling resistance of concretes with reduced clinker content.show moreshow less

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  • Bei diesem Dokument handelt es sich um die Übersetzung meiner deutschsprachigen Dissertation ins Englische.

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Metadaten
Document Type:Doctoral Thesis
Author:Dr.-Ing. Matthias MüllerORCiDGND
DOI (Cite-Link):https://doi.org/10.25643/bauhaus-universitaet.4868Cite-Link
URN (Cite-Link):https://nbn-resolving.org/urn:nbn:de:gbv:wim2-20230103-48681Cite-Link
URL:https://e-pub.uni-weimar.de/opus4/frontdoor/index/index/docId/4502
Title Additional (German):Frost-Tausalz-Angriff auf Beton - Neue Erkenntnisse zum Schadensmechnismus
Referee:Prof. Dr.-Ing. Michael HaistORCiDGND, Prof. Dr.-Ing. Christoph Müller
Advisor:Prof. Dr.-Ing. Horst-Michael LudwigORCiDGND
Language:English
Date of Publication (online):2022/12/23
Year of first Publication:2022
Date of final exam:2021/07/21
Release Date:2023/01/03
Publishing Institution:Bauhaus-Universität Weimar
Granting Institution:Bauhaus-Universität Weimar, Fakultät Bauingenieurwesen
Institutes and partner institutions:Fakultät Bauingenieurwesen / Professur Werkstoffe des Bauens
Tag:Concrete; Cryogenic Suction; Damage mechanism; Glue Spall; Salt frost attack
GND Keyword:Beton; Frost
Dewey Decimal Classification:600 Technik, Medizin, angewandte Wissenschaften
BKL-Classification:56 Bauwesen
Licence (German):License Logo Creative Commons 4.0 - Namensnennung-Nicht kommerziell-Keine Bearbeitung (CC BY-NC-ND 4.0)
Note:
Englische Fassung meiner deutschsprachigen Dissertation mit dem Titel "Frost-Tausalz-Angriff auf Beton - Neue Erkenntnisse zum Schadensmechnismus".