@inproceedings{ThielGehlen, author = {Thiel, Charlotte and Gehlen, Christoph}, title = {On the determination of carbonation in cementitious materials}, series = {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}, booktitle = {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}, publisher = {RILEM}, isbn = {978-2-35158-217-6}, pages = {373 -- 380}, abstract = {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.}, language = {en} } @incollection{ThielStengelGehlen, author = {Thiel, Charlotte and Stengel, T. and Gehlen, Christoph}, title = {Life cycle assessment (LCA) of road pavement materials}, series = {Eco-efficient Construction and Building Materials}, booktitle = {Eco-efficient Construction and Building Materials}, publisher = {Woodhead Publishing}, doi = {10.1533/9780857097729.2.368}, pages = {368 -- 403}, abstract = {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.}, language = {en} } @article{ThielGoetzfriedGehlen, author = {Thiel, Charlotte and Goetzfried, Franz Xaver and Gehlen, Christoph}, title = {Physikalische und chemische Auswirkungen von tauenden Chloriden auf Betone von Verkehrsbauwerken}, series = {Straße und Autobahn}, volume = {64}, journal = {Straße und Autobahn}, number = {9}, publisher = {Kirschbaum}, pages = {684 -- 688}, abstract = {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.}, language = {de} } @article{KesslerThielGrosseetal., author = {Kessler, Sylvia and Thiel, Charlotte and Grosse, Christian U. and Gehlen, Christoph}, title = {Effect of freeze-thaw damage on chloride ingress into concrete}, series = {Materials and Structures}, volume = {50}, journal = {Materials and Structures}, number = {2}, publisher = {Springer}, doi = {10.1617/s11527-016-0984-4}, abstract = {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.}, language = {en} } @article{OlssonAbdulWahidNilssonetal., author = {Olsson, Nilla and Abdul Wahid, Fatmawati and Nilsson, Lars-Olof and Thiel, Charlotte and Wong, Hong S. and Baroghel-Bouny, V{\´e}ronique}, title = {Wick action in mature mortars with binary cements containing slag or silica fume - The relation between chloride and moisture transport properties under non-saturated conditions}, series = {Cement and Concrete Research}, volume = {111}, journal = {Cement and Concrete Research}, number = {September}, publisher = {Elsevier}, doi = {10.1016/j.cemconres.2018.06.006}, pages = {94 -- 103}, abstract = {Moisture and ionic transport under non-saturated condition is an important, but poorly understood transport phenomena particularly for mature systems containing supplementary cementitious materials. This paper investigates the moisture and chloride profiles of 3-year old mortars containing Portland cement (OPC), slag and silica fume (SF) after long-term (30-48 months) wick action exposure in 1.09 M NaCl solution. Moisture profiles were measured with ¹H NMR relaxometry and chloride profiles with microXRF. The measured profiles were discussed in relation to moisture dependent material properties such as chloride diffusion coefficients, moisture diffusion coefficients, and desorption isotherms. Results show that the combination of different cementitious materials, e.g. the cementitious binder, is the key factor affecting chloride penetration depth. The cementitious binder also strongly affects chloride diffusion coefficient, moisture diffusion coefficient and chloride binding properties, which are all important parameters for the prediction of chloride ingress.}, language = {en} } @article{VandenHeedeThielDeBelie, author = {Van den Heede, Philip and Thiel, Charlotte and De Belie, Nele}, title = {Natural and accelerated carbonation behaviour of high-volume fly ash (HVFA) mortar: Effects on internal moisture, microstructure and carbonated phase proportioning}, series = {Cement and Concrete Composites}, volume = {113}, journal = {Cement and Concrete Composites}, number = {October}, publisher = {Elsevier}, doi = {10.1016/j.cemconcomp.2020.103713}, abstract = {Binders with large portions of carbon-intensive Portland cement replaced by supplementary cementitious materials (e.g. fly ash) are more susceptible to carbonation mainly due to their lower CO2 buffering capacity. This conclusion is usually drawn from accelerated experiments at elevated CO2 levels involving processes that seriously differ from natural carbonation. The resulting presence of H2O reactant in the pore system and the carbonated microstructure itself may be very different. In this paper, these phenomena were investigated for High-Volume Fly Ash (HVFA) mortar via carbonation tests at ±0.04\% CO2 (natural carbonation), 1\% CO2 and 10\% CO2. Internal humidity sensor monitoring and 1H NMR relaxometry revealed the highest water vapour and liquid water contents after carbonation at 10\% CO2. Carbonation at 10\% CO2 results in a coarser pore structure than carbonation at 1\% CO2, and this probably due to a higher degree of C-S-H carbonation.}, language = {en} } @article{ThielSkarabisGehlenetal., author = {Thiel, Charlotte and Skarabis, Jens and Gehlen, Christoph and Goetzfried, Franz Xaver}, title = {Einfluss des Sulfatgehalts von Tausalzen auf den Frost-Tausalz-Widerstand von Betonen im Bereich der Bundesfernstraßen}, series = {Straße und Autobahn}, journal = {Straße und Autobahn}, number = {11}, publisher = {Kirschbaum}, pages = {811 -- 815}, language = {de} } @inproceedings{ThielHolmeErlacheretal., author = {Thiel, Charlotte and Holme, L. and Erlacher, L. and Gehlen, Christoph}, title = {Effect of real climatic conditions on freeze-thaw induced damage of concrete}, series = {Durable Concrete for Infrastructure under Severe Conditions : Smart admixtures, self-responsiveness and nano-additions, Proceedings 10-11 September 2019, Ghent, Belgium}, booktitle = {Durable Concrete for Infrastructure under Severe Conditions : Smart admixtures, self-responsiveness and nano-additions, Proceedings 10-11 September 2019, Ghent, Belgium}, editor = {Adelaide Ara{\´u}jo, Maria and Van Tittelboom, Kim}, isbn = {978-9-463-88638-3}, abstract = {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.}, language = {en} } @incollection{ThielGehlen, author = {Thiel, Charlotte and Gehlen, Christoph}, title = {Nuclear Magnetic Resonance and Magnetic Resonance Imaging}, series = {Methods of Measuring Moisture in Building Materials and Structures}, booktitle = {Methods of Measuring Moisture in Building Materials and Structures}, publisher = {Springer}, doi = {10.1007/978-3-319-74231-1_13}, pages = {99 -- 108}, abstract = {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.}, language = {en} } @article{GehlenThielStengel, author = {Gehlen, Christoph and Thiel, Charlotte and Stengel, Thorsten}, title = {{\"O}kobilanz f{\"u}r die Herstellung und Nutzung eines Autobahnabschnitts}, series = {Griffig : Aktuelles {\"u}ber Verkehrsfl{\"a}chen aus Beton}, journal = {Griffig : Aktuelles {\"u}ber Verkehrsfl{\"a}chen aus Beton}, number = {1}, publisher = {G{\"u}tegemeinschaft Verkehrsfl{\"a}chen aus Beton e.V.}, pages = {16}, abstract = {Im Rahmen einer nachhaltigen Entwicklung hat sich u.a. Deutschland dazu verpflichtet, klimasch{\"a}digende 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 {\"O}kobilanz ermittelt und miteinander verglichen. Durch Ber{\"u}cksichtigung der Verkehrsbelastung w{\"a}hrend einer dreißigj{\"a}hrigen Nutzungsdauer werden die Auswirkungen des Treibstoffverbrauchs verdeutlicht. M{\"o}gliche Einsparpotentiale werden dargelegt.}, language = {de} } @incollection{LatasteHansenNilssonetal., author = {Lataste, Jean-Fran{\c{c}}ois and Hansen, Kurt Kielsgaard and Nilsson, Lars-Olof and Thiel, Charlotte and Schießl-Pecka, Angelika and G{\"o}ller, Arndt and Gehlen, Christoph}, title = {Spatial Distributions}, series = {Methods of Measuring Moisture in Building Materials and Structures}, booktitle = {Methods of Measuring Moisture in Building Materials and Structures}, publisher = {Springer}, doi = {10.1007/978-3-319-74231-1_19}, pages = {173 -- 190}, abstract = {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.}, language = {en} } @inproceedings{GehlenThiel, author = {Gehlen, Christoph and Thiel, Charlotte}, title = {Specification of building materials for in service durability}, series = {Proceedings ICSBM 2019: 2nd international conference of sustainable building materials, 2019, Eindhoven}, booktitle = {Proceedings ICSBM 2019: 2nd international conference of sustainable building materials, 2019, Eindhoven}, publisher = {Technische Universiteit Eindhoven}, address = {Eindhoven}, isbn = {978-90-386-4898-9}, pages = {31 -- 40}, abstract = {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.}, language = {en} } @incollection{HansenLatasteThiel, author = {Hansen, Kurt Kielsgaard and Lataste, Jean-Fran{\c{c}}ois and Thiel, Charlotte}, title = {ND-Methods - From a Surface}, series = {Methods of Measuring Moisture in Building Materials and Structures}, booktitle = {Methods of Measuring Moisture in Building Materials and Structures}, publisher = {Springer}, doi = {10.1007/978-3-319-74231-1_21}, pages = {193 -- 198}, abstract = {A complicated application is to measure a moisture distribution with depth from a surface non-destructively. Only a few methods are suitable for such a case.}, language = {en} } @incollection{NilssonAgostiniThiel, author = {Nilsson, Lars-Olof and Agostini, Franck and Thiel, Charlotte}, title = {Installation of Probes}, series = {Methods of Measuring Moisture in Building Materials and Structures}, booktitle = {Methods of Measuring Moisture in Building Materials and Structures}, publisher = {Springer}, doi = {10.1007/978-3-319-74231-1_23}, pages = {207 -- 219}, language = {en} } @inproceedings{ThielSchoenGehlen, author = {Thiel, Charlotte and Schoen, Alex and Gehlen, Christoph}, title = {Einfluss der CO2-Permeation auf die Carbonatisierung zementgebundener Baustoffe}, series = {Tagungsbericht: Ibausil, 20. Internationale Baustofftagung, 12.-14. September 2018, Weimar}, booktitle = {Tagungsbericht: Ibausil, 20. Internationale Baustofftagung, 12.-14. September 2018, Weimar}, publisher = {Bauhaus-Universit{\"a}t Weimar}, pages = {153 -- 161}, language = {de} } @inproceedings{ThielLowkeGehlen, author = {Thiel, Charlotte and Lowke, Dirk and Gehlen, Christoph}, title = {Effect of minimum temperature, salt and moisture content on concrete under freeze-thaw deicing salt attack}, series = {ICDC 2012 : International Congress on Durability of Concrete; Trondheim, Norway, 18-21 June 2012}, booktitle = {ICDC 2012 : International Congress on Durability of Concrete; Trondheim, Norway, 18-21 June 2012}, publisher = {Norwegian Concrete Association}, doi = {10.13140/2.1.3243.9367}, abstract = {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.}, language = {en} } @inproceedings{ThielBeddoeLowkeetal., author = {Thiel, Charlotte and Beddoe, Robin E. and Lowke, Dirk and Gehlen, Christoph}, title = {Accelerated carbonation: changes in water transport, porosity and phases of mortar due to different CO 2 pressures}, series = {Proceedings of the 10th fib International PhD Symposium in Civil Engineering, July 21 to 23, 2014, Qu{\´e}bec, Canada}, booktitle = {Proceedings of the 10th fib International PhD Symposium in Civil Engineering, July 21 to 23, 2014, Qu{\´e}bec, Canada}, organization = {F{\´e}d{\´e}ration International du B{\´e}ton (fib)}, pages = {217 -- 221}, abstract = {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).}, language = {en} } @inproceedings{ThielBeddoe, author = {Thiel, Charlotte and Beddoe, Robin E.}, title = {Investigating the role of moisture on concrete carbonation using single-sided H-NMR}, series = {International RILEM Conference on Materials, Systems and Structures in Civil Engineering 2016 - Conference segment on Moisture in Materials and Structures, 22-24 August 2016, Lyngby, Denmark}, booktitle = {International RILEM Conference on Materials, Systems and Structures in Civil Engineering 2016 - Conference segment on Moisture in Materials and Structures, 22-24 August 2016, Lyngby, Denmark}, publisher = {RILEM Publications S.A.R.L.}, isbn = {978-2-35158-171-1}, pages = {261 -- 268}, abstract = {Accelerated test methods are commonly used in order to predict concrete carbonation in natural concentrations. Here, specimens are carbonated at high CO 2 concentrations at a specified temperature and relative humidity. However, the transfer of laboratory results to field behaviour remains difficult because CO 2 transport is affected by the original moisture content of the specimens and additional moisture formed by the carbonation reaction. Therefore knowledge on moisture transport and content during carbonation is required. Specimens made with Ordinary Portland cement and a water/cement ratio 0.50 were exposed to 0.05, 2 and 10 vol.\% CO 2 for 28 days. Single-sided NMR moisture profiles were determined before, during and after carbonation. It is shown that moisture content increases due to carbonation at high CO 2 10 \%) in the beginning of the exposure. An increase in capillary pore water in front and behind the carbonation front could be observed even after 28d. During natural carbonation moisture changes are mainly due to the change in porosity produced by the carbonation reactions. It is shown that changes in phase composition and thus porosity dominate the carbonation process in cement-based materials. Therefore, the suitability of high CO 2 concentrations is limited for an accelerated test that reflects field condition. Single-sided 1 H NMR proved to be a valuable tool to investigate moisture transport in concrete non-destructively.}, language = {en} } @inproceedings{ThielLowkeGehlen, author = {Thiel, Charlotte and Lowke, Dirk and Gehlen, Christoph}, title = {Detection of Transport Processes during Freeze-Thaw Deicing Salt Attack Using Single-Sided NMR}, series = {Microstructural-related durability of cementitious composites : Second International Conference on Microstructural-related Durability of Cementitious Composites, 11 - 13 April 2012, Amsterdam}, booktitle = {Microstructural-related durability of cementitious composites : Second International Conference on Microstructural-related Durability of Cementitious Composites, 11 - 13 April 2012, Amsterdam}, publisher = {RILEM}, abstract = {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.}, language = {en} } @inproceedings{ThielKesslerChilleetal., author = {Thiel, Charlotte and Keßler, Sylvia and Chill{\´e}, R. and Gehlen, Christoph}, title = {Effect of internal freeze-thaw deterioration on chloride migration in concrete}, series = {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}, booktitle = {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}, publisher = {CRC Press}, abstract = {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.}, language = {en} }