TY - GEN A1 - Thiel, Charlotte A1 - Gehlen, Christoph A1 - Föstl, Florian T1 - Service life prediction of concrete under freeze-thaw deicing salt attack with intermittent dry periodst T2 - The Sixth International Symposium on Life-Cycle Civil Engineering : IALCCE 2018,28 -31.10.2018, Ghent Y1 - 2018 ER - TY - GEN A1 - Gehlen, Christoph A1 - Thiel, Charlotte T1 - Schnellprüfverfahren zur Bestimmung des Karbonatisierungswiderstandes T2 - Proceedings, 59. BetonTage : Betone der Zukunft, Neu-Ulm, 24.-26.02.2015 Y1 - 2015 PB - Bauverl. ER - TY - JOUR A1 - Thiel, Charlotte A1 - Kratzer, Johanna A1 - Grimm, Benedikt A1 - Kränkel, Thomas A1 - Gehlen, Christoph T1 - Effect of Internal Moisture and Outer Relative Humidity on Concrete Carbonation JF - CivilEng N2 - With steadily rising CO2 concentrations in the ambient air and fast-changing concretecompositions with reduced clinker contents, the availability of reliable and accelerated concrete car-bonation tests is of crucial importance to design durable structures. This paper focuses on the effectsof moisture under accelerated conditions and the effects of different CO2 exposure conditions. Mor-tar prisms incorporating three different cement types were cured and stored at either 50% or 65%relative humidity (RH). Afterwards, the prisms were carbonated at different ambient humidities(50, 57 and 65%), different CO2 concentrations (0.04, 1 and 3 vol.%) and complemented by a seriesof tests at increased gas pressure (2 barg). High-resolution test methods were used to explain theunderlying carbonation mechanisms. The results show that pre-conditioning for two weeks—ascurrently suggested by the European Standard—seems to be too short because the initial inner mois-ture content severely affects the carbonation rate. Relative humidity during carbonation of 57% ledto higher carbonation rates compared to 50% and 65%. In addition, climate data needs to be period-ically (preferably permanently) recorded in research experiments and in laboratory testing to ensurefair interpretation of experimental results. KW - accelerated carbonation KW - concrete KW - moisture KW - durability KW - relative humidity Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-56091 N1 - Corresponding author: Charlotte Thiel VL - 4 IS - 3 SP - 1039 EP - 1052 PB - MDPI CY - Basel ER - TY - CHAP A1 - Thiel, Charlotte A1 - Haynack, Alexander A1 - Geyer, Sebastian A1 - Gehlen, Christoph A1 - Braun, Alexander ED - Pereira, Eduardo B. ED - Barros, Joaquim A. O. ED - Figueiredo, Fabio P. T1 - CarboDB-Open Access Database for Concrete Carbonation T2 - Proceedings of the 3rd RILEM Spring Convention and Conference (RSCC 2020), Volume 1: Strategies for a Resilient Built Environment, March 9-14, 2020, Guimarães, Portugal N2 - Sustainable service life design of reinforced concrete structures relies on accurate input values. However, in the field of carbonation induced corrosion some input parameters and statistical distributions still need to be validated for worldwide climate conditions. Furthermore, many well-published literature data is not considered due to different storage conditions. At the suggestion of CEN/TC 104/SC1/WG1 the database “CarboDB” was created providing open access to extensive information on concrete carbonation under different storage conditions. The natural carbonation coefficient as well as the minimum concrete cover can be calculated for chosen situations. CarboDB provides reliable data on concrete carbonation in order to increase existing knowledge on concrete carbonation. The database is available online at http://carbodb.bgu.tum.de//. By registration further contribution is possible and appreciated. New insights can be gained by merging several sources. For natural carbonation, testing only up to 140 days underestimates the carbonation progress of concretes with limestone fillers and high amount of ground granulated blast furnace slag. KW - Carbonation KW - Service life design KW - Data management KW - Compliance testing KW - Supplementary cementicious materials Y1 - 2021 SN - 978-3-030-76547-7 U6 - https://doi.org/10.1007/978-3-030-76547-7_8 SP - 79 EP - 90 PB - Springer International Publishing CY - Cham ER - TY - CHAP A1 - Gehlen, Christoph A1 - Mayer, Till Felix A1 - Thiel, Charlotte A1 - Fischer, Christian T1 - Lebensdauerbemessung T2 - Beton Kalender 2021 : Fertigteile, Integrale Bauwerke N2 - Christoph Gehlen, Till Felix Mayer, Charlotte Thiel und Christian Fischer beschreiben die Lebensdauerbemessung von Beton. Umfassend werden Transport‐ und Schädigungsmodelle vorgestellt, die die Mechanismen der Carbonatisierung, der Chlorideindringung, der Korrosion und der korrosionsinduzierten Rissbildung im Stahlbeton beschreiben. Die damit einhergehende Verbundthematik wird erläutert. Auch wird auf alle Mechanismen der Betonkorrosion eingegangen. Die Bemessung in Bezug auf die Dauerhaftigkeit und damit Abschätzungen für die Lebensdauer von Beton wird in drei unterschiedlich genauen Formaten geführt. Neben dem vollprobabilistischen Format wird beschrieben, wie Bemessungen auch auf Grundlage von Nachweisen basierend auf Teilsicherheitsbeiwerten durchgeführt werden können. Daran anschließend wird aufgezeigt, welche deskriptiven Bemessungsansätze sich daraus ableiten lassen. An einigen exemplarisch herausgegriffenen Objektbeispielen wird die Lebensdauerbemessung konkret vorgeführt. Y1 - 2021 U6 - https://doi.org/10.1002/9783433610206.ch1 VL - 110 SP - 1 EP - 57 PB - Wilhelm Ernst & Sohn ER - TY - JOUR A1 - Haynack, Alexander A1 - Sekandar, Zadran A1 - Jithender, J. Timothy A1 - Gambarelli, Serena A1 - Kränkel, Thomas A1 - Thiel, Charlotte A1 - Ozbolt, Josko A1 - Gehlen, Christoph T1 - Can a Hend-Held 3D Scanner Capture Temperature-Induced Strain of Mortar Samples? Comparison between Experimental Measurements and Numerical Simulations JF - mathematics N2 - The expected lifespan of cement-based materials, particularly concrete, is at least 50 years. Changes in the pore structure of the material need to be considered due to external influences and associated transport processes. The expansion behaviour of concrete and mortar during freeze–thaw attacks, combined with de-icing salt agents, is crucial for both internal and external damage. It is essential to determine and simulate the expansion behaviour of these materials in the laboratory, as well as detect the slow, long-term expansion in real structures. This study measures the expansion of mortar samples during freeze–thaw loading using a high-resolution hand-held 3D laser scanner. The specimens are prepared with fully or partially saturated pore structures through water storage or drying. During freeze–thaw experiments, the specimens are exposed to pure water or a 3% sodium chloride solution (NaCl). Results show contraction during freezing and subsequent expansion during thawing. Both test solutions exhibit similar expansion behaviour, with differences primarily due to saturation levels. Further investigations are required to explore the changing expansion behaviour caused by increasing microcracking resulting from continuous freeze–thaw cycles. A numerical analysis using a 3D coupled hygro-thermo-mechanical (HTM) model is conducted to examine the freeze–thaw behaviour of the mortar. The model accurately represents the freezing deformation during the freeze–thaw cycle. KW - concrete KW - mortar KW - durability KW - freeze–thaw and de-icing salt resistance KW - strain KW - 3D laser scanning KW - numerical simulation KW - 3D FE numerical model KW - hygro-thermo-mechanical coupling Y1 - 2023 U6 - https://doi.org/10.3390/math11173672 VL - 11 IS - 17 PB - MDPI CY - Basel ER - TY - CHAP A1 - Thiel, Charlotte A1 - Gehlen, Christoph T1 - On the determination of carbonation in cementitious materials T2 - Challenges in Design and Management of Structures. Proceedings of the International Conference on Sustainable Materials Systems and Structures (SMSS2019) Durability, Monitoring and Repair of Structures, 18.-22.03.2019, Rovinja, Croatio N2 - For material testing, qualification and subsequent assessment fast, simple, reliable and economic methods are needed. This paper provides an overview of different techniques to determine the depth of carbonation in cementitious materials. The easiest and cheapest way is to remove a core or a fragment of concrete cover and spray a colour indicator on the fresh fractured surface (by splitting). Here, 1 % phenolphthalein in 70 % ethanol is most widely used. However, this only indicates in which area the concrete has a pH value below 8.2-10, but not the actual carbonation front which is on average about 20 % higher. Since phenolphthalein is carcinogenic, alternative colour indicators were investigated in the laboratory. 0.5 % Curcumin showed similar colour change to phenolphthalein. In addition, 0.1 % thymolphthalein proved to be an alternative. Scattering within one measurement was lower than for phenolphthalein and the results were closer to the carbonation depths determined by different analytical methods (TGA and LA-ICP-MS). Furthermore, the transition pH-value of thymolphthalein is in the area of 9.3-10.5 which is closer to the actual carbonation front, allowing a more accurate assessment of the risk of reinforcement corrosion. KW - Carbonation KW - colour indicators KW - test methods Y1 - 2019 SN - 978-2-35158-217-6 SN - 978-2-35158-225-1 SN - 978-2-35158-218-3 SP - 373 EP - 380 PB - RILEM ER - TY - CHAP A1 - Thiel, Charlotte A1 - Stengel, T. A1 - Gehlen, Christoph T1 - Life cycle assessment (LCA) of road pavement materials T2 - Eco-efficient Construction and Building Materials N2 - At present the choice of materials and techniques in road construction is dictated by structural requirements and economic aspects. However, ecological factors have gained in importance due to environmental considerations in politics and society. To evaluate the environmental impact of motorways, a life cycle assessment (LCA) according to ISO 14040 was carried out for different pavement types. By investigating different case scenarios, the reduction potential of environmental impact was quantified. The biggest reduction in air pollution can be achieved by improving pavement properties (e.g., texture, stiffness and flatness) which would significantly reduce the fuel consumption of vehicles. KW - asphalt roads KW - concrete roads KW - life cycle assessment KW - pavement LCA Y1 - 2014 U6 - https://doi.org/10.1533/9780857097729.2.368 SP - 368 EP - 403 PB - Woodhead Publishing ER - TY - JOUR A1 - Thiel, Charlotte A1 - Goetzfried, Franz Xaver A1 - Gehlen, Christoph T1 - Physikalische und chemische Auswirkungen von tauenden Chloriden auf Betone von Verkehrsbauwerken JF - Straße und Autobahn N2 - Zur Untersuchung des Einflusses von Loesungen der Tausalze Natriumchlorid, Calciumchlorid und Magnesiumchlorid auf die Dauerhaftigkeit von Beton wurden unter praxisnahen Bedingungen im Labor Betonprobekoerper, mit typischen Qualitaeten fuer Verkehrsbauwerke, unterschiedlichen Belastungszyklen unterzogen. Auch bei extremer Belastung durch wiederholte Nass- und Trockenphasen mit anschliessenden zyklischen Frost-Tau-Wechseln waren die physikalischen und chemischen Auswirkungen auf die Betone gering. Die festgestellten Unterschiede der verschiedenen Tausalze im Schaedigungsverhalten sind fuer die Praxis vernachlaessigbar. Fuer die Winterdienstpraxis laesst sich die Schlussfolgerung ziehen, dass zur Herstellung von Feuchtsalz im Hinblick auf die Dauerhaftigkeit von Strassenbeton und XF4-Beton die Loesungen der Chloride von Natrium, Calcium und Magnesium gleichermassen geeignet sind. Auch bei vorbeugender Fluessigstreuung mit NaCl-Sole ist auf Fahrbahnen mit normkonform zusammengesetztem Beton lediglich ein extrem geringer Angriff zu erwarten. (A) ABSTRACT IN ENGLISH: To investigate the influence of solutions of the de-icing salts sodium chloride, calcium chloride and magnesium chloride onto the durability of concrete, concrete specimens, with typical qualities for roads and bridges, were subjected to different load cycles under practical conditions. Also in the case of extreme load through repeated wet and dry phases with subsequent cyclical freeze-thaw-attack the physical and chemical effects on the concrete were low. The found differences of the different de-icing salts in the damage behaviour are negligible for the practice. The results prove that for the generation of pre-wetted salt, the solutions of the chlorides of sodium, calcium and magnesium are equally suitable with regard to the durability of concrete used in road construction and of XF4 concrete. Also in the case of preventive liquid spraying with NaCI-brine only an extremely small attack is to be expected on roads constructed with concrete conform to the current standards. Y1 - 2013 VL - 64 IS - 9 SP - 684 EP - 688 PB - Kirschbaum ER - TY - JOUR A1 - Kessler, Sylvia A1 - Thiel, Charlotte A1 - Grosse, Christian U. A1 - Gehlen, Christoph T1 - Effect of freeze–thaw damage on chloride ingress into concrete JF - Materials and Structures N2 - In cold climates, reinforced concrete structures (RCSs) are frequently and severely damaged by freeze–thaw (FT) and deicing-salt attack during winter periods. FT action can also cause additional water uptake known as frost suction. If a critical degree of water saturation is exceeded, severe deterioration of the microstructure of the concrete is likely, enhancing chloride ingress and increasing the probability of corrosion of its reinforcement. We present herein a test method to characterize the resistance of concrete to FT and chloride ingress. Chloride migration tests were performed on concretes with different degrees of FT deterioration, with and without deicing agents. The performance of RCSs is decisively affected under these combined actions. Quantitative description of the resulting FT damage is achieved using ultrasonic measurements and resonance frequency analysis. The test results confirm that the latter nondestructive test method provides more reliable evaluation of FT damage compared with usual ultrasonic pulse velocity measurements. Different concretes with supplementary cementitious materials and different degrees of FT deterioration with and without deicing agents were tested. While concrete made with air-entraining agents clearly showed the best FT resistance, concrete with ground-granulated blast-furnace slag showed superior resistance to both chloride migration and FT attack, both being positively affected by appropriate curing conditions. KW - Chloride ingress KW - Combined environmental attack KW - Freeze–thaw damage KW - Resonance frequency analysis KW - Ultrasonic measurement Y1 - 2017 U6 - https://doi.org/10.1617/s11527-016-0984-4 VL - 50 IS - 2 PB - Springer ER - TY - JOUR A1 - Thiel, Charlotte A1 - Skarabis, Jens A1 - Gehlen, Christoph A1 - Goetzfried, Franz Xaver T1 - Einfluss des Sulfatgehalts von Tausalzen auf den Frost-Tausalz-Widerstand von Betonen im Bereich der Bundesfernstraßen JF - Straße und Autobahn Y1 - 2010 UR - https://www.researchgate.net/publication/350344182_Einfluss_des_Sulfatgehalts_von_Tausalzen_auf_den_Frost-Tausalz-Widerstand_von_Betonen_im_Bereich_der_Bundesfernstrassen IS - 11 SP - 811 EP - 815 PB - Kirschbaum ER - TY - CHAP A1 - Thiel, Charlotte A1 - Holme, L. A1 - Erlacher, L. A1 - Gehlen, Christoph ED - Adelaide Araújo, Maria ED - Van Tittelboom, Kim T1 - Effect of real climatic conditions on freeze-thaw induced damage of concrete T2 - Durable Concrete for Infrastructure under Severe Conditions : Smart admixtures, self-responsiveness and nano-additions, Proceedings 10-11 September 2019, Ghent, Belgium N2 - The analysis of German weather data from 1996 to 2019 reveals a development in climate towards freeze-thaw exposure conditions which are detrimental to concrete durability. This trend may intensify freeze-thaw attack in future and lead to more internal and/or external damage in concrete structures. This contribution considers the inclusion of real climate conditions in laboratory simulations. Weather data were recorded and compared with depth-resolved measurements of humidity and temperature in concrete samples stored at the median site of an expressway. The strength of attack depends mainly on the amount of damaging freeze-thaw cycles (minimum temperature <-5°C in combination with moisture). In addition, the salt content of the contact water, minimum temperature and thickness of the ice layer on the concrete surface are decisive. Experiments show that internal and to a minor degree also external damage increase due to lower heating rates. The exposure of the sample itself (i.e. compass direction and removal of snow) affects the resulting damage evolution significantly. In order to save resources and enable the production of more sustainable concrete structures, current accelerated tests need to be adapted to real climatic conditions. 1. Introduction Adaptation to climate change and the associated extreme weather events represents a crucial challenge for our society. The durability of concrete, the most frequently used building material, is highly dependent on the local environment of concrete structures. In the case of a freeze-thaw de-icing salt attack, this is given by essentially the number of frost-thaw cycles (FTC) relevant to damage, the minimum temperature, the thickness of the ice layer, the moisture conditions and the concentration of salt. By investigating the interdependencies, the depth of scaling of the concrete surface per winter period can be predicted as a function of parameters accounting for the different effects of the concrete composition (air content, w/b ratio and binder type), curing time, carbonation and the duration and formation of damaging freeze-thaw cycles, [1, 2]. In order to quantify the individual effects and map them in an engineering model, a large number of laboratory tests are necessary. For this purpose, a known freeze-thaw cycle usually has to be modified. While it is already known that the cooling rate [3] and holding time at minimum temperature [4] affect scaling development, we investigated the effect of different heating rates on scaling on freeze-thaw de-icing salt attack. KW - Freeze-thaw deicing salt attack KW - heating rate KW - field exposure KW - climate weather data KW - moisture uptake Y1 - 2019 UR - https://www.sintef.no/globalassets/project/lorcenis/completed-proceedings_version20191025_lorceniswebsite.pdf SN - 978-9-463-88638-3 ER -