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 - Thiel, Charlotte A1 - Lowke, Dirk A1 - Gehlen, Christoph T1 - Effect of minimum temperature, salt and moisture content on concrete under freeze-thaw deicing salt attack T2 - ICDC 2012 : International Congress on Durability of Concrete; Trondheim, Norway, 18-21 June 2012 N2 - While in the field of reinforcement corrosion service life prediction is well-established, there is still need for a user-friendly design model in the field of freeze-thaw deicing salt attack. This attack is one of the major causes of damage to concrete structures in cold climates. The degree of moisture during the first freeze-thaw-cycles exceeds moisture saturation by capillary suction and diffusion. When a critical degree of saturation is reached before freezing damage occurs immediately. As a consequence, depending on the concrete resistance (e.g. pore structure of the concrete) and the severeness of the freeze-thaw load (e.g. minimum temperature, moisture offer and salt concentration), a certain number of freeze-thaw cycles is needed before damage occurs (initial phase). The main exposure parameters influencing the initial phase as well as the subsequent evolution of damage (deterioration phase) are the minimum temperature as well as the salt and moisture content. These factors were determined by single-sided NMR, gravimetry and mercury intrusion porosimetry respectively. Three different concrete compositions were exposed to freeze-thaw deicing salt load at different minimum temperatures. To investigate the influence of the initial moisture content concrete specimens were continuously exposed to freeze-thaw load while other specimens from the same batch were exposed to alternating freeze-thaw exposure with intermediate dry periods. It was found that the minimum temperature and intermediate dry periods had a significant influence on the initial phase as well as on the degradation phase. In addition, higher chloride content in the near-surface concrete reduced the scaling rate. The chloride content under freeze-thaw exposure with 3% NaCl solution in laboratory significantly exceeded typical contents due to capillary suction and diffusion. Increasing the minimum temperature increased the chloride content. The investigations form the basis for service life prediction of concrete towards freeze-thaw deicing salt attack. KW - freeze-thaw deicing salt attack KW - moisture movement Y1 - 2012 U6 - https://doi.org/10.13140/2.1.3243.9367 PB - Norwegian Concrete Association 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 - 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 - 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 - Gehlen, Christoph T1 - Nuclear Magnetic Resonance and Magnetic Resonance Imaging T2 - Methods of Measuring Moisture in Building Materials and Structures N2 - Nuclear Magnetic Resonance (NMR) enables to quantify the hydrogen nuclei in a sample and thus indirectly the water content. Here, hydrogen nuclei are put in oscillation (resonance) by applying a magnetic field and additional irradiation with pulsed electromagnetic waves of certain frequencies. In case all hydrogen nuclei of a sample are exclusively bound in water molecules, the resulting initial amplitude of the detected NMR signal is directly proportional to the water content. The subsequent attenuation of the oscillation is caused by relaxation mechanisms and provides information on the mobility and thus the binding states of the hydrogen nuclei. Therefore even the pore size distribution can be determined in completely water-saturated samples. If the magnetic field is graded, images can be created based on spatially resolved nuclei density distributions (MRI). Depending on the research objective, tailored choice of equipment and settings can be used to qualitatively and mostly quantitatively analyze almost every moisture-related problem. The article gives an overview of the existing NMR methods, equipment, influencing parameters, calibration techniques, applications and limitations. Y1 - 2018 U6 - https://doi.org/10.1007/978-3-319-74231-1_13 SP - 99 EP - 108 PB - Springer 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 - TY - CHAP A1 - Thiel, Charlotte A1 - Lowke, Dirk A1 - Gehlen, Christoph T1 - Praxisgerechte Modellierung des Schädigungsverlaufs von Betonen unter Frost-Tausalz-Angriff -Einfluss der Austrocknung T2 - Tagungsbericht / IBAUSIL, 18. Internationale Baustofftagung : 12.-15. September 2012, Weimar, Band 2 Y1 - 2012 SN - 978-3-00-034075-8 PB - Bauhaus-Univ. ER - TY - CHAP A1 - Grimm, Benedikt A1 - Münchmeyer, Sebastian A1 - Kränkel, Thomas A1 - Gehlen, Christoph A1 - Thiel, Charlotte T1 - Developing a New Rapid, Relevant, and Reliable (R3) Method for Accelerated Measurement of Carbonation Progress at Gas Overpressure T2 - International RILEM Conference on Synergising expertise towards sustainability and robustness of CBMs and concrete structures, SynerCrete’23 - Volume 1 N2 - The determination of durability-relevant material resistances of concrete is of great importance. They serve as input to engineering models to predict the durability of structures under real environmental conditions. The natural resistances have to be determined in time-consuming experiments, since the processes in nature are very slow. This is particularly important for new materials where long-term experience is not yet available. Thus, accelerated testing is required. Only that way new materials can be evaluated regarding their durability and subsequently be used in practical applications. For carbonation, a new R3 accelerated test method is presented in this contribution. An automated carbonation pressure chamber was developed. It consists of a pressure vessel, automated in such a way that it can apply gas overpressure of various intensities up to 8 bar to mortar and concrete samples. Simultaneously, it can control and regulate the ambient CO2 concentration from 0 to 99.5% in a fully automated and continuously variable procedure. Experiments were carried out with varying combinations of gas overpressure at CO2 concentrations of 3 vol.-% to achieve the most time-efficient carbonation of mortars and concretes. Mortars with different material compositions were used to evaluate the general suitability of the test procedure with the developed equipment. The automated carbonation pressure chamber enables reliable carbonation testing with a total duration under accelerated conditions of only 7 days. KW - Carbonation KW - concrete KW - durability KW - accelerated testing KW - gas overpressure Y1 - 2023 U6 - https://doi.org/10.1007/978-3-031-33211-1_30 SP - 336 EP - 346 PB - Springer ER - TY - CHAP A1 - Thiel, Charlotte A1 - Schoen, Alex A1 - Gehlen, Christoph T1 - Einfluss der CO2-Permeation auf die Carbonatisierung zementgebundener Baustoffe T2 - Tagungsbericht: Ibausil, 20. Internationale Baustofftagung, 12.-14. September 2018, Weimar Y1 - 2018 SP - 153 EP - 161 PB - Bauhaus-Universität Weimar ER - TY - JOUR A1 - Gehlen, Christoph A1 - Thiel, Charlotte A1 - Stengel, Thorsten T1 - Ökobilanz für die Herstellung und Nutzung eines Autobahnabschnitts JF - Griffig : Aktuelles über Verkehrsflächen aus Beton N2 - Im Rahmen einer nachhaltigen Entwicklung hat sich u.a. Deutschland dazu verpflichtet, klimaschädigende Emissionen zu reduzieren. Luftschadstoffe werden zu erheblichen Teilen durch den Straßenverkehr verursacht. Die potentiellen Umweltwirkungen, die bei der Herstellung und Nutzung eines 1 km langen Autobahnabschnitts mit vier verschiedenen Oberbauarten wurden in einer Ökobilanz ermittelt und miteinander verglichen. Durch Berücksichtigung der Verkehrsbelastung während einer dreißigjährigen Nutzungsdauer werden die Auswirkungen des Treibstoffverbrauchs verdeutlicht. Mögliche Einsparpotentiale werden dargelegt. Y1 - 2010 UR - https://www.guetegemeinschaft-beton.de/fileadmin/guetegemeinschaft-beton-de/media/Redaktion/PDF-Dateien/Griffig_1_2010_Ansichts.pdf IS - 1 SP - 16 PB - Gütegemeinschaft Verkehrsflächen aus Beton e.V. ER - TY - CHAP A1 - Franke, Wolfram A1 - Thiel, Charlotte A1 - Duran, F. A1 - Gehlen, Christoph T1 - Effect of Calcium Nitrate on the freeze-thaw-resistance of concrete T2 - Proceedings of the 2nd International Congress on Concrete Durability, 2, 2014, New Delhi N2 - Concrete in cold climates is not only exposed to cold weather while concreting but also to freeze-thaw cycles during its lifetime. Thus not only the concrete production needs to be adjusted to the environmental conditions but also the mixture has to be durable and resist the environmental impacts. Commonly an air entraining agent is used to interrupt the capillary pore system and to provide further space for the freezing water to expand. The downside of this approach is a loss in compressive strength. Within this paper the effect of simultaneous use of air entraining agent and calcium nitrate is discussed. It is shown that calcium nitrate can counteract strength loss due to the air entraining agent without reducing the durability gain in the same extent. A certain combination of calcium nitrate and air entraining agent can also be used to increase the freeze-thaw-resistance. KW - air entrainer KW - calcium nitrate KW - Durability KW - freeze-thaw-resistance Y1 - 2014 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 - 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 - Beddoe, Robin E. A1 - Lowke, Dirk A1 - Gehlen, Christoph T1 - Accelerated carbonation: changes in water transport, porosity and phases of mortar due to different CO 2 pressures T2 - Proceedings of the 10th fib International PhD Symposium in Civil Engineering, July 21 to 23, 2014, Québec, Canada N2 - Currently, the carbonation resistance of concrete is assessed on the basis of accelerated tests performed with high (unrealistic) CO2 concentrations. It remains unclear whether these high concentrations reflect the processes occurring under natural conditions and enable the accurate prediction of field behaviour. To develop future test procedures with higher reliability, it is necessary to deepen the knowledge on the mechanisms of carbonation. Thin slices of mortar were stored in a gaseous mixture of 2 % CO2 and 98 % N2 at atmospheric pressure or 5 bar. IH-NMR equipment was used to detennine moisture profiles with aresolution of 0.2 mm. At 5 bar a drying front at the near-surface region of the mortar discs severely inhibited the progression of the carbonation reactions. This effect was prevented by exposure to altemating cycles of pressure and storage at atmospheric pressure (65%RH) which significantly increased the rate of carbonation, but was too severe to resolve the effect of cement type on carbonation resistance. Furthermore , the evolution of water beyond the carbonation front of mortar sampies under accelerated concentration and at atmospheric pressure was clearly visible. This may lead to an overestimation of carbonation resistance of sampies tested under accelerated conditions at the optimal relative humidity for natural carbonation (50-70% RH). Y1 - 2014 UR - https://mediatum.ub.tum.de/doc/1230854/1230854.pdf SP - 217 EP - 221 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 - CHAP A1 - Thiel, Charlotte A1 - Keßler, Sylvia A1 - Chillé, R. A1 - Gehlen, Christoph T1 - Effect of internal freeze-thaw deterioration on chloride migration in concrete T2 - Life-Cycle and Sustainability of Civil Infrastructure Systems : proceedings of the third International Symposium on Life-Cycle Civil Engineering, Vienna, Austria, 3 - 6 October 2012 N2 - Depending on the specific exposure conditions, reinforced concrete structures (RCS) are simultaneously subjected to different physical and chemical loads. While in the field of reinforcement corrosion, service life prediction based on full-probabilistic models is well-established, the consequences of combined attack have been neglected until now. The most frequent “load” combination on RCS in cold climates are freeze-thaw attack which can lead to inner or outer damage and chloride ingress which can lead to reinforcement corrosion. In an experimental study four different concrete compositions are exposed either to a defined freeze-thaw attack or stored in moist environment. Afterwards, the chloride migration coefficient of the specimens which were both exposed to freeze-thaw-cycles and not, was determined with a modified rapid chloride migration test. The results clearly show an influence of freeze-thaw-induced internal damage on chloride ingress depending on concrete composition. Y1 - 2012 PB - CRC Press ER - TY - CHAP A1 - Lataste, Jean-François A1 - Hansen, Kurt Kielsgaard A1 - Nilsson, Lars-Olof A1 - Thiel, Charlotte A1 - Schießl-Pecka, Angelika A1 - Göller, Arndt A1 - Gehlen, Christoph T1 - Spatial Distributions T2 - Methods of Measuring Moisture in Building Materials and Structures N2 - In many applications moisture measurements are made to estimate the moisture differences between different points in a structure. Here, it is often more important to use a “simple” method that is easy and rapid to use in many points instead of necessarily obtain the exact moisture level in each point. The objective with “moisture indications” like that could very well be to select points where more accurate moisture measurements are to be made. The measuring principle to apply is of course a trade-off between accuracy and simplicity. Y1 - 2018 U6 - https://doi.org/10.1007/978-3-319-74231-1_19 SP - 173 EP - 190 PB - Springer ER - TY - CHAP A1 - Thiel, Charlotte A1 - Gehlen, Christoph T1 - Compliance testing for probabilistic durability design purposes T2 - Proceedings of the Sixth International Symposium on Life-Cycle Civil Engineering (IALCCE 2018), 28-31 October 2018, Ghent, Belgium Y1 - 2018 PB - Taylor & Francis ER - TY - CHAP A1 - Thiel, Charlotte A1 - Lowke, Dirk A1 - Gehlen, Christoph T1 - Detection of Transport Processes during Freeze-Thaw Deicing Salt Attack Using Single-Sided NMR T2 - Microstructural-related durability of cementitious composites : Second International Conference on Microstructural-related Durability of Cementitious Composites, 11 - 13 April 2012, Amsterdam N2 - Damage of concrete structures exposed to a combined freeze-thaw deicing salt attack (FTDSA) is one of the major deterioration mechanisms in cold climates. Before damage occurs, concrete structures subjected to freeze-thaw cycles (FTC) in the presence of water or deicing salt solution exhibit fast moisture uptake known as frost suction. There is still need for research in describing and modelling the mechanisms that lead to freeze-thaw induced surface scaling of concrete. Therefore, the moisture transport under FTDSA was investigated using single-sided 1 H NMR. The technique enables the observation of dynamic transport processes of water inside the sample non-destructively. Furthermore, porosity and pore size distribution of water saturated samples can be determined. The method also provides information on the mobility of water, i.e. water in capillaries or in gel pores. Water redistribution in pores as well as changes in the pore structure inside the near surface concrete sample under FTDSA were observed with single-sided 1 H NMR. The measurements confirmed the additional saturation of gel pores during thawing previously described by the micro ice lens model. The results are discussed within the context of the mechanisms of freeze-thaw deicing salt attack of concrete and contribute to a deeper understanding of the mechanisms that lead to freeze-thaw deterioration of concrete. Y1 - 2012 PB - RILEM 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 - CHAP A1 - Gehlen, Christoph A1 - Thiel, Charlotte T1 - Specification of building materials for in service durability T2 - Proceedings ICSBM 2019: 2nd international conference of sustainable building materials, 2019, Eindhoven N2 - To assess whether a structural element made of a given building material can withstand the expected mechanical load and environmental exposure in service, designers need information on the material resistances and loads as well as the local conditions. The durability of a building material in the structure can only be assessed if these factors are taken into account. Usually, the material resistances are obtained from laboratory tests. However, the performance of materials under standardized laboratory conditions differs from those occurring in the field. This paper considers this assessment problem and develops a solution strategy based on carbonation-induced corrosion as an example. Y1 - 2019 SN - 978-90-386-4898-9 SP - 31 EP - 40 PB - Technische Universiteit Eindhoven CY - Eindhoven 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 - 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 - CHAP A1 - Haynack, Alexander A1 - Schneider, Alexander A1 - Timothy, Jithender J. A1 - Kränkel, Thomas A1 - Gehlen, Christoph A1 - Thiel, Charlotte T1 - Effect of Chloride Concentration on the Freeze-Thaw Resistance of Concrete T2 - International RILEM Conference on Synergising expertise towards sustainability and robustness of CBMs and concrete structures, SynerCrete’23 - Volume 2 N2 - Performance test methods intend to provide a fast, accurate and precise determination of a particular building material property and thus determine the associated material performance. In concrete, various performance tests are used to classify existing or to approve new materials, to compare concrete compositions or to determine causes of damage in existing structures. The challenge of such test methods is to accelerate natural (very slow) mechanisms to determine the material performance precisely within a short time. However, the attack on the material must not be unrealistically intensive, but must represent reality, just in fast motion. The performance tests used to demonstrate the freeze-thaw resistance of concrete employ a 3% NaCl solution, with literature data ranging from 1% to 10% showing that low concentrations can result in higher surface scaling. In this paper, mortar and concrete specimens are tested at 0, 1, 3, 6, and 9% NaCl solution following the CDF procedure (DIN CEN/TS 12390-9:2017-05). The results are discussed against the background of the existing literature and show that the damage is critically dependent on the pore system and thus also on the effect of the micro-ice lens pump. With increasing freeze-thaw exposition, the pessimum in the external damage shifts towards a de-icing salt concentration of 6%. Furthermore, a novel test methodology based on 3D-laserscanning is presented to determine scaling accurately by eliminating side effects that are typically present in current standards. KW - Concrete KW - durability KW - freeze-thaw resistance KW - chloride concentration KW - 3D laser scanning Y1 - 2023 U6 - https://doi.org/10.1007/978-3-031-33187-9_83 SP - 911 EP - 921 PB - Springer CY - Cham 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 - JOUR A1 - Haynack, Alexander A1 - Timothy, Jithender J. A1 - Kränkel, Thomas A1 - Gehlen, Christoph A1 - Thiel, Charlotte T1 - Analyse des Frost‐Tausalz‐Widerstands zementgebundener Baustoffe mittels 3D‐Laserscanning JF - ce/papers: Proceedings in Civil Engineering N2 - Eine Herausforderung performancebasierter Prüfverfahren zur Bewertung der Dauerhaftigkeit ist die Beschleunigung natürlicher Mechanismen. Dies ist notwendig, um innerhalb kurzer Zeit die Langzeit-Leistungsfähigkeit ermitteln zu können. Die Bestimmung der Frost-Tausalzbeständigkeit von Beton kann durch den CDF-Test erfolgen, welcher für Betone mit ausreichendem Frost-Tausalz-Widerstand sehr gut funktioniert. Bei Proben mit einer unzureichenden bzw. unbekannten Performance können erhöhte Randabwitterungen auftreten, welche durch das Ablösen des seitlichen Abdichtbands entstehen. Der zunehmende Randeinfluss führt so zu einer Verfälschung der Ergebnisse und zu einer Unterschätzung der tatsächlichen Performance des Bauteils. In diesem Beitrag werden Mörtel- und Betonprobekörper mit unterschiedlichen Abwitterungsraten in Anlehnung an das CDF-Verfahren untersucht. Zusätzlich wird die Oberflächenschädigung der Proben anhand einer neuartigen Messmethode mittels hochauflösendem 3D-Laserscanning ausgewertet. Die Ergebnisse zeigen, dass die Randeffekte mit der Laserscan-Methode umgangen und vergleichbare Ergebnisse zu den CDF-Untersuchungen erzielt werden können. Somit können Betone ohne Randeinflüsse charakterisiert und eine präzise Prognose der Langzeitbeständigkeit getroffen werden. KW - Beton KW - Mörtel KW - Frost-Tausalz-Widerstand KW - Dauerhaftigkeit KW - 3D-Laserscanning Y1 - 2023 U6 - https://doi.org/10.1002/cepa.2951 SN - 2509-7075 VL - 6 IS - 6 SP - 1189 EP - 1196 PB - Ernst & Sohn ER - TY - JOUR A1 - Grimm, Benedikt A1 - Thiel, Charlotte A1 - Kränkel, Thomas A1 - Gehlen, Christoph T1 - Einfluss der Permeation auf die Carbonatisierung von Beton JF - ce/papers: Proceedings in Civil Engineering N2 - Die Carbonatisierung von Beton kann einerseits zu Schäden bei Stahlbetonbauwerken führen, andererseits kann der Beton so CO2 speichern und damit seinen CO2-Fußabdruck verringern. In diesem Beitrag wird dargestellt, wie eine effiziente Beschleunigung der Carbonatisierung durch Anlegen eines geringen äußeren Drucks erreicht werden kann. Damit wird neben der Diffusion der wesentlich schneller ablaufende Transportmechanismus der Permeation ausgenutzt, der das CO2 tiefer in das Probeninnere transportiert und damit in kurzer Zeit die Bestimmung des Carbonatisierungswiderstand zementgebundener Materialien ermöglicht. Hierzu wurde eine Prüfeinrichtung entwickelt, die es ermöglicht, die CO2-Konzentration und in gewissen Grenzen auch relative Luftfeuchte sowie die Temperatur gezielt einzustellen und zu steuern, um so Mörtel- und Betonproben schnell und präzise zu carbonatisieren. Der Einfluss verschiedener Druckstufen und Wechselzyklen wird dargelegt und die resultierenden chemischen und physikalischen Veränderungen der Proben bestimmt. Als besonders effizient und gleichzeitig realitätsnah erwies sich die konstante CO2-Beaufschlagung mit 3 Vol.-% CO2 mit zusätzlichem, moderatem Gasdruck. Das hier entwickelte Verfahren kann daher genutzt werden, um Betone schnell und effizient in zeitraffenden Materialtests hinsichtlich Carbonatisierungswiderstand zu charakterisieren. KW - Beton KW - Carbonatisierung KW - Prüfverfahren KW - Gasdruck KW - Permeation Y1 - 2023 U6 - https://doi.org/10.1002/cepa.3005 SN - 2509-7075 VL - 6 IS - 6 SP - 1348 EP - 1357 PB - Ernst & Sohn CY - Berlin ER -