TY - CONF A1 - Strangfeld, Christoph T1 - Frequency modulated, air-coupled ultrasound generated by fluidic oscillators N2 - The majority of ultrasonic devices used for non- destructive testing in civil engineering require contact with the surface of the concrete (specimen), which significantly increases the time required for the measurement. This makes it impractical for extensive investigation of large-scale structures such as bridge decks, foundations, or tunnels. In a pioneering approach, fluidic oscillators are used as contact free ultrasonic sources to overcome the aforementioned limi- tations. These robust and cost-effective actuators require only pressurised air and are ideally suited for harsh environments. At a constant supply pressure, they generate a continuous mono- frequent actuation signal. Further, varying the supply pressure via a fast pressure regulator was found to generate a frequency modulated signal which enabled time-of-flight measurement with an added advantage of increased signal to noise ratio. To demonstrate the feasibility of this novel idea of non-contact ultrasound, the results of the initial tests are presented. T2 - IEEE International Ultrasound Symposium CY - Venice, Italy DA - 11.10.2022 KW - Air-coupled ultrasound KW - Frequency modulation KW - Non-destructive testing KW - Civil engineering KW - Building materials KW - Fluidic oscillators PY - 2022 AN - OPUS4-56072 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - In situ Prozessüberwachung und Qualitätskontrolle bei der additiven Fertigung von Betonbauteilen N2 - In der additiven Fertigung von Beton wird kontinuierlich Material gemischt und verarbeitet. Dies erfordert eine kontinuierliche in situ Prozessüberwachung und Qualitätskontrolle. An der BAM wurde ein 3D-Betondrucker aufgebaut, der eine umfängliche Prozessüberwachung ermöglicht. Druck-, Temperatur- und Feuchtesensoren in der Pumpe und im Fördersystem erlauben ein kontinuierliches Monitoring des Frischbetons, während ein Laserlinienscanner am Druckkopf unmittelbar die gedruckte Ist-Kontur verfolgt. Die so gewonnenen Daten können Grundlage für die Erarbeitung von Normen für die additive Fertigung von Betonbauteilen sein und somit deren Standsicherheit gewährleisten. T2 - 63. For‍schungs‍kol‍lo‍qui‍um des Deutschen Ausschuss für Stahlbeton CY - Berlin, Germany DA - 16.10.2024 KW - Additive Fertigung KW - Beton KW - Frischbetoncharakterisierung KW - Extrusionsdruck PY - 2024 AN - OPUS4-61390 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jeyifous, Olubunmi Anthony A1 - Schönsee, Eric A1 - Strangfeld, Christoph A1 - Hüsken, Götz T1 - Correlation of continuously measured in-line process parameters and extruded geometry in 3D concrete printing experiments N2 - Additive manufacturing of concrete structures is a novel and emerging tech-nology. Free contouring in civil engineering, which allows for entirely new designs, is a significant advantage. Although several techniques and ap-proaches demonstrate these advantages, quality control during printing is highly challenging and rarely applied. Due to the continuous mixing process used in 3D concrete printing, it is impossible to exclude variations in the dry mixture or water content, and a single test sample is insufficient to represent the whole structure. A defect in one layer during printing can affect the in-tegrity of the entire structure. Therefore, continuous and real-time process monitoring is required to record and document the printing process. At the Bundesanstalt für Materialforschung und -prüfung (BAM), a test rig for 3D concrete printing was developed to monitor the properties during the printing process. This study investigates the relationship between geometric accuracy and process parameters (pressure, pump torque, print speed, layer height, water content) in extrusion-based 3D concrete printing. Using a high-precision laser scanner, the geometric measurements of printed concrete ele-ments are evaluated in real-time. The concrete elements are printed under controlled conditions with varied process parameters. Preliminary findings indicate a significant correlation between process variables and geometric ac-curacy. T2 - Fourth RILEM International Conference on Concrete and Digital Fabrication CY - Munich, Germany DA - 04.09.2024 KW - 3D concrete printing KW - Geometric accuracy KW - Process monitoring KW - Quality control PY - 2024 DO - https://doi.org/10.1007/978-3-031-70031-6_15 SP - 127 EP - 133 AN - OPUS4-61534 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Strangfeld, Christoph A1 - Klewe, Tim ED - Rizzo, P. ED - Milazzo, A. T1 - Hygrometric Moisture Measurements Based on Embedded Sensors to Determine the Mass of Moisture in Porous Building Materials and Layered Structures N2 - Subfloors are layered structures, consisting largely of porous building materials, such as screed. They are often suffering damage from tap water leakage, which is a typical problem in buildings, and which has largely contributed to repair costs of almost 3 billion Euro in 2018 alone in Germany. In this context, especially mould plays a role, which is both destroying the structure and posing severe health risks. To determine the damaging effects of moisture, it is necessary to know the respective processes occurring in building materials, especially to quantify the amount of moisture and its progress in the material. In this study, humidity sensors are used to derive the material moisture experimentally. Capacitive sensors recording the relative humidity are embedded into the screed and in the insulation materials such as expanded polystyrene, extruded polystyrene, perlite and glass wool. For the application in screed, the sensors need to be shielded against the aggressive alkaline materials. To ensure an appropriate exchange with the environment, a permeable membrane is requested. Different membrane materials have been investigated regarding their robustness and their permeability. In the first experimental setup, two humidity sensor arrays with seven individual sensors are embedded in homogeneous screed samples. The measured corresponding relative humidity of the screed is converted to the material moisture based on the approach of Hillerborg. In a second experimental setup, a layered structure of a complete subfloor is built in a box of 0.8 m times 0.8 m. The humidity sensors are positioned in the different insulation materials of various thicknesses. By adding water, leakage damage is simulated and its progress and effect is investigated experimentally. The investigations point at the question if the observed moisture is able to generate damage such as mould. The moisture and corresponding humidity values are discussed. It will be shown that this low-cost hygrometric approach can be used easily for moisture monitoring of screed and insulation materials as well KW - Moisture monitoring KW - Material moisture KW - Building materials KW - Embedded humidity sensors PY - 2021 DO - https://doi.org/10.1007/978-3-030-64594-6_22 VL - 1 SP - 213 EP - 225 PB - Springer Nature CY - Cham AN - OPUS4-52013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller-Vahl, H. F. A1 - Strangfeld, Christoph A1 - Nayeri, C. N. A1 - Paschereit, C. O. A1 - Greenblatt, D. T1 - Dynamic Stall Under Combined Pitching and Surging N2 - Dynamic stall often occurs under conditions of simultaneous unsteady pitching and surging (e.g., rotorcraft and wind turbines), butmanymodels employ a dimensionless time base that implicitly assumes that surging is superimposed, in a quasi-steady manner, on dynamic pitching. An unsteady wind tunnel was used to examine this assumption, where a technique was developed to quantify the unsteady effects of surging on a pitching NACA 0018 airfoil. The technique involved performing multiple harmonic pitching experiments under nominally steady freestream conditions that bracketed a corresponding 50% surging amplitude (1.25 ⋅ 105 ≤ Re ≤ 3.75 ⋅ 105). By interpolating these data, unsteady-pitching/quasi-steady-surging data sets were constructed and compared with de facto synchronous pitch and surging experiments, thereby isolating the unsteady effects of surging on a pitching airfoil. Both large and small poststall maximum angles of attack (αs + 5° and αs + 15°) were considered at multiple pitch-surge phase differences. During deep dynamic stall (αs � 15°), with large-scale separation, surging was seen to have a secondary effect on the unsteady aerodynamics. However, at small poststall maximum angles of attack (αs + 5°), either light or deep dynamic stall behavior was observed depending upon the pitch-surge phase difference. This was attributed to Reynolds number history effects, exemplified by boundary-layer transition, and thus it can be referred to as “transitional” dynamic stall. KW - Dynamic stall KW - Angle of attack oscillations KW - Free stream velocity osciallations PY - 2020 DO - https://doi.org/10.2514/1.J059153 VL - 58 IS - 12 SP - 5134 EP - 5145 PB - American Institute of Aeronautics and Astronautics AN - OPUS4-51037 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Völker, Tobias A1 - Millar, Steven A1 - Strangfeld, Christoph A1 - Wilsch, Gerd T1 - Identification of type of cement through laser-induced breakdown spectroscopy N2 - The composition of concrete determines its resistance to various degradation mechanisms such as ingress of ions, carbonation or reinforcement corrosion. Knowledge of the composition of the hardened concrete is therefore helpful to assess the remaining service life of an existing structure or evaluate the damage observed during inspections. For example, for most existing concrete structures the type of cement originally used is not known and must therefore be determined afterwards. This paper presents a preliminary study on the application of laser-induced breakdown spectroscopy (LIBS) to identify the type of cement. For this purpose, ten different types of cement were investigated. For every type, three cement paste prisms were produced: (i) prisms dried, ground and pressed into tablets, (ii) prisms dried and (iii) prisms untreated. LIBS measurements were performed with a diode-pumped low energy laser (1064 nm, 3 mJ, 1.5 ns, 100 Hz) in combination with two compact spectrometers which cover the UV and NIR spectral range. A reduced subset of spectral features was used to build a classification model based on linear discriminant analysis. The results show that the classification of homogenized pressed cement powder samples provides a high accuracy, however, factors such as a different sample matrix and moisture content can affect the accuracy of the classification. The study demonstrates that LIBS is a promising tool to identify the type of cement. KW - Spectroscopy KW - LIBS KW - Cement KW - Classification KW - Identification PY - 2020 DO - https://doi.org/10.1016/j.conbuildmat.2020.120345 VL - 258 SP - 120345 PB - Elsevier Ltd. AN - OPUS4-51157 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - TC 286-GDP STAR - chapter: Modelling moisture transport in porous media N2 - The current content and structure of the chapter "Modelling moisture transport in porous media" of the state of the art report is presented. T2 - RILEM Spring Convention 2021 CY - Online meeting DA - 06.04.2021 KW - Moisture transport KW - Porous media KW - Modelling mass transfer KW - Gas diffusion KW - Concrete PY - 2021 AN - OPUS4-52405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin A1 - Schweitzer, T. A1 - Maack, Stefan A1 - Strangfeld, Christoph T1 - Influence of operating conditions on the fluidic ultrasonic transducer signal N2 - While contact and immersion ultrasonic testing are established methods in non-destructive testing (NDT), generating high power air-coupled ultrasound remains a challenging task. Solutions often involve setups that are restricted to lab environments. When field measurements are required, such as in NDT for civil engineering, a handy, robust and safe transducer is needed. For this purpose, an ultrasonic transducer based on a fluidic switch has been developed. A sonic air flow inside the device is switched rapidly so that an ultrasonic signal is generated. Both theory and previous flow simulations suggest that the control flow pressure ramp has only little influence on the switching time of the device. This publication gives an overview over the operating principle of the fluidic ultrasonic transducer and investigates the influence of control tube length and pulsing repetition rate on the ultrasonic pressure amplitude. High repetition rates are found to reduce the signal amplitude, whereas long tubing has only little negative influence on the amplitude while improving signal quality. T2 - 47. Jahrestagung für Akustik (DAGA 2021) CY - Vienna, Austria DA - 15.08.2021 KW - Ultrasound KW - Non-destructive testing KW - Fluidic devices PY - 2021 UR - https://pub.dega-akustik.de/DAGA_2021 SN - 978-3-939296-18-8 SP - 48 EP - 51 CY - Berlin, Germany AN - OPUS4-53493 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Stoppel, M. A1 - Bartholmai, Matthias A1 - Petrov, Sergej A1 - Fakhouri, A. T1 - Embedded RFID-sensors for concrete bridge structures N2 - In the near future, it will be important to adopt innovative approaches and technologies in order to further guarantee the reliability and availability of the highway network. New tools are therefore needed in order 'to obtain in-depth information about the condition of bridges and its development early enough before significant, precarious damage cases occur. In 2011, the research program "Intelligente Brücken (Smart Bridges)" was launched by the BASt together with the BMVI to evolve systems for information and holistic evaluation for bridge structures as a supplement to the current inspection-based maintenance management. Several projects dealt with the topic in the last few years and provided guidelines and a solid basis to move towards a first implementation considering the input of all research projects carried out so far. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 PY - 2015 SN - 1435-4934 SP - P 54, 1061 EP - 1063 AN - OPUS4-34720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Müller-Vahl, H. A1 - Nayeri, C. N. A1 - Paschereit, C. O. A1 - Greenblatt, D. T1 - Airfoil in a high amplitude oscillating stream N2 - A combined theoretical and experimental investigation was carried out with the objective of evaluating theoretical predictions relating to a two-dimensional airfoil subjected to high amplitude harmonic oscillation of the free stream at constant angle of attack. Current theoretical approaches were reviewed and extended for the purposes of quantifying the bound, unsteady vortex sheet strength along the airfoil chord. This resulted in a closed form solution that is valid for arbitrary reduced frequencies and amplitudes. In the experiments, the bound, unsteady vortex strength of a symmetric 18 % thick airfoil at low angles of attack was measured in a dedicated unsteady wind tunnel at maximum reduced frequencies of 0.1 and at velocity oscillations less than or equal to 50 %. With the boundary layer tripped near the leading edge and mid-chord, the phase and amplitude variations of the lift coefficient corresponded reasonably well with the theory. Near the maximum lift coefficient overshoot, the data exhibited an additional high-frequency oscillation. Comparisons of the measured and predicted vortex sheet indicated the existence of a recirculation bubble upstream of the trailing edge which sheds into the wake and modifies the Kutta condition. Without boundary layer tripping, a mid-chord bubble is present that strengthens during flow deceleration and its shedding produces a dramatically different effect. Instead of a lift coefficient overshoot, as per the theory, the data exhibit a significant undershoot. This undershoot is also accompanied by high-frequency oscillations that are characterized by the bubble shedding. In summary, the location of bubble and ist subsequent shedding play decisive roles in the resulting temporal aerodynamic loads. KW - vortex shedding KW - aerodynamics KW - general fluid mechanics PY - 2016 DO - https://doi.org/10.1017/jfm.2016.126 SN - 0022-1120 VL - 2016 IS - 793 SP - 79 EP - 108 AN - OPUS4-35594 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Einsatzfähigkeit von RFID-Tags zur Identifikation und Diagnose von Bauteilen in der intelligenten Straßeninfrastruktur T2 - Symposium "Intelligente Brücken" der BASt CY - Bergisch Gladbach, Deutschland DA - 2015-11-30 PY - 2015 AN - OPUS4-34997 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Multimethodische Bestimmung von Feuchtegradienten in Estrich N2 - Um den Feuchtegehalt von Fußbodenestrich vor der Verlegung von Holz- oder anderen Bodenbelägen zu bestimmen, werden zerstörende Prüfverfahren wie die Calcium-Carbid Methode (CM) oder das thermogravimetrische Darr-Verfahren eingesetzt. Diese liefern jedoch einmalig nur punktuelle Informationen und sind je nach Estrichtyp auch störanfällig. Zusammen mit Partnern aus Forschung und Industrie wurde an der BAM ein Ringversuch durchgeführt, dessen Ziel es war, verschiedene nach Möglichkeit zerstörungsfreie oder – arme Prüfverfahren hinsichtlich ihrer Genauigkeit und Sensitivität vor allem im Bereich der Belegereife zu testen. Hier dargestellt sind die Ergebnisse aufgenommen an einer Calciumsulphat-Estrich Probe vom Typ Knauf FE80 Largo mit drei Verfahren, die auch Aussagen über die Feuchtegradienten in die Tiefe zulassen. Die Proben wurden bei Konstant-Normklima mit T=23 °C und rH=50 % zur Trocknung gelagert. T2 - Bauwerksdiagnose 2016 CY - Berlin, Germany DA - 25.02.2016 KW - Feuchtemessung KW - Estrich KW - Sensorik PY - 2016 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. AN - OPUS4-35478 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kruschwitz, Sabine A1 - Strangfeld, Christoph A1 - Wöstmann, Jens T1 - Measuring screed moisture with EM methods – a comparison of capacitive handheld and microwave resonator probes N2 - We have compared the performance of the typical Darr and CM moisture testing techniques, which are destructive with several non-destructive testing techniques on two types of floor screeds. In case of cement based screeds these destructive tests failed to deliver reliable results. Moreover, our measurements indicate significantly different drying and moisture transport behavior for the investigated cement based and calcium-sulphate based screeds. Whereas we have strong with depth decreasing moisture gradients in the CT material, we observe in the penetrated volumes of our ndt methods basically no clear moisture gradient in the CA samples. The findings with ndt methods could be supported by moisture gradient studies with nuclear magnetic resonance measurements. T2 - 11th Int. Conference on electromagnetic wave interaction with water and moist substances CY - Florenz, Italy DA - 23.5.2016 KW - Moisture KW - Screed KW - Microwave KW - Nuclear magnetic resonance PY - 2016 SP - 77 EP - 84 AN - OPUS4-36674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bartholmai, Matthias A1 - Johann, Sergej A1 - Kammermeier, Michael A1 - Müller, Maximilian A1 - Strangfeld, Christoph T1 - Transmission characteristics of RFID sensor systems embedded in concrete N2 - Completely embedded sensor systems for long-term operation offer innovative possibilities for structural health monitoring of concrete structures. Measuring of relevant parameters, e.g., temperature, humidity, or indication of corrosion can be performed with low energy sensors. This allows to implement passive RFID sensor systems without cable connection and battery, which are power supplied exclusively by the electromagnetic field from the external reader device. To evaluate characteristics and conditions of this concept, a systematical investigation of the transmission characteristics with variation of relevant parameters, as communication frequency, installation depth, type of concrete, moisture content, etc. is currently carried out in an interdisciplinary research project at BAM. First results are presented in this paper. T2 - IEEE Sensors 2016 CY - Orlando, FL, USA DA - 30.10.2016 KW - Embedded sensors KW - Energy harvesting KW - Wireless sensors KW - RFID sensors KW - Transmission characteristics KW - Structural health monitoring PY - 2016 SN - 978-1-4799-8287-5 SN - 1930-0395 SP - 1541 EP - 1543 PB - IEEE AN - OPUS4-38388 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Intelligent bridge: the durabasttest bridge equipped with RFID-based sensors N2 - The duraBASt area at the highway intersection “Köln-Ost” is a large test field for road testing. It includes the duraBASt test bridge which is ca. 66 m long and 14.25m broad. This bridge is part of the “road in the 21st century” project and is equipped with several sensors for structural health monitoring. This feasibility study is realised to construct intelligent bridges in the future. Quantities like temperature, strain, moisture, corrosion, etc. are measured by embedded sensors. In the presented work, the focus lays on passive RFID-based sensors. The communication and energy supply is realised by a mobile transmitter through the concrete cover. Hence, no cables or batteries are required. The sensors are design to withstand in the alkaline environment in concrete. Thus, moisture and corrosion are detectable for several decades. T2 - Structural Materials Technology 2016 CY - Portland, ME, USA DA - 29.08.2016 KW - RFID based sensors KW - SHM in civil engineering PY - 2016 AN - OPUS4-37466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Kruschwitz, Sabine A1 - Wöstmann, Jens A1 - Munsch, Sarah Mandy A1 - Hase, Felix T1 - Moisture in screed: a non-destructive multi-sensor approach N2 - Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23◦ C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes. T2 - 8th European Workshop On Structural Health Monitoring CY - Bilbao, Spain DA - 05.07.2016 KW - NMR KW - Screed KW - Embedded sensors KW - Moisture KW - Corresponding relative humidity PY - 2016 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. SP - 1 EP - 11 AN - OPUS4-36814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture in screed: a non-destructive multi-sensor approach N2 - Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23° C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes. T2 - EWSHM 2016 CY - Bilbao, Spain DA - 05.07.2016 KW - Moisture KW - Screed KW - Embedded sensors KW - Corresponding relative humidity KW - NMR PY - 2016 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. AN - OPUS4-36840 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture Measurements with RFID based Sensors in Screed and Concrete N2 - To quantify the moisture in concrete, RFID based humidity sensors are embedded. Passive high frequency, ultra-high frequency RFID tags as well as active Bluetooth sensors are tested. After concreting, all sensors measure the corresponding relative humidity to monitor the concrete moisture. Two case studies are performed, embedding in an existing construction, i.e. the duraBASt test bridge, and embedding in cement based mortar in the laboratory. As basis for robust and long-life sensors in alkaline concrete, different casing materials are tested. Furthermore, signal strength measurements and their sensitivity to different moisture levels are performed. T2 - EWSHM 2016 CY - Bilbao, Spain DA - 05.07.2016 KW - Moisture measurements KW - RFID based sensors KW - DuraBASt KW - Humidity sensors KW - Long-life sensor casing PY - 2016 AN - OPUS4-36834 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Kruschwitz, Sabine T1 - Multimethodische Bestimmung von Feuchtegradienten in Estrich N2 - Um den Feuchtegehalt von Fußbodenestrich vor der Verlegung von Holz- oder anderen Bodenbelägen zu bestimmen, werden zerstörende Prüfverfahren wie die Calcium-Carbid Methode (CM) oder das thermogravimetrische Darr-Verfahren eingesetzt. Diese liefern jedoch einmalig nur punktuelle Informationen und sind je nach Estrichtyp auch störanfällig. Zusammen mit Partnern aus Forschung und Industrie wurde an der BAM ein Ringversuch durchgeführt, dessen Ziel es war, verschiedene nach Möglichkeit zerstörungsfreie oder – arme Prüfverfahren hinsichtlich ihrer Genauigkeit und Sensitivität vor allem im Bereich der Belegereife zu testen. Hier dargestellt sind die Ergebnisse aufgenommen an einer Calciumsulphat-Estrich Probe vom Typ Knauf FE80 Largo mit drei Verfahren, die auch Aussagen über die Feuchtegradienten in die Tiefe zulassen. Die Proben wurden bei Konstant-Normklima mit T=23 °C und rH=50 % zur Trocknung gelagert. T2 - Fachtagung Bauwerksdiagnose CY - Berlin, Germany DA - 25.02.2016 KW - Estrich KW - Nuklear Magnetische Resonanz KW - Elektrischer Widerstand KW - Feuchtegehalt KW - Zerstörungsfreie Prüfverfahren PY - 2016 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. AN - OPUS4-36994 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bartholmai, Matthias A1 - Johann, Sergej A1 - Kammermeier, Michael A1 - Müller, Maximilian A1 - Strangfeld, Christoph T1 - RFID sensor systems embedded in concrete – systematical investigation of the transmission characteristics N2 - Long-term completely embedded sensor systems offer innovative possibilities for structural health monitoring of concrete structures. Measuring of relevant parameters, e.g., temperature, humidity, or indication of corrosion can be performed with low energy sensors. This allows to implement passive RFID sensor systems without cable connection and battery, which are power supplied exclusively by the electromagnetic field from the external reader device. To evaluate characteristics and conditions of this concept, a systematical investigation of the transmission characteristics with variation of relevant parameters, as communication frequency, installation depth, type of concrete, moisture content, etc. is currently carried out in an interdisciplinary research project at BAM. First results are presented in this paper. T2 - 8th European Workshop On Structural Health Monitoring CY - Bilbao, Spain DA - 05.07.2016 KW - Structural health monitoring KW - Embedded sensor KW - Energy harvesting KW - Wireless sensors KW - RFID sensors KW - Transmission characteristics PY - 2016 SP - 1 EP - 5 AN - OPUS4-37129 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Embedded RFID-sensors for concrete bridge structures N2 - In the near future, it will be important to adopt innovative approaches and technologies in order to further guarantee the reliability and availability of the highway network. New tools are therefore needed in order to obtain in-depth information about the condition of bridges and its development early enough before significant, precarious damage cases occur. In 2011, the research program “Intelligente Brücken (Smart Bridges)” was launched by the BASt together with the BMVI to evolve systems for information and holistic evaluation for Bridge structures as a supplement to the current inspection-based maintenance management. Several projects dealt with the topic in the last few years and provided guidelines and a solid basis to move towards a first implementation considering the input of all research projects carried out so far. T2 - International Symposium Non-Destructive Testing in Civil Engineering CY - Berlin, Germany DA - 15.09.2015 KW - RFID based sensors KW - Embedded sensors KW - Structural health monitoring KW - Concrete condition monitoring PY - 2015 AN - OPUS4-37626 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Johann, Sergej A1 - Strangfeld, Christoph A1 - Müller, Maximilian A1 - Bartholmai, Matthias ED - Aulova, Alexandra ED - Rogelj Ritonja, Alenka ED - Emri, Igor T1 - RFID sensor systems embedded in concrete - requirements for long-term operation N2 - One of the more difficult tasks for structural health monitoring is the continuous evaluation of the stability and load capacity of the building materials. This knowledge can be won, e.g., by taking material samples at the examining place with the drawback of partly destroying the structure. To avoid this, modern sensor and communication technologies offer promising methods for non-destructive testing. To address the tasks for monitoring of concrete structures, in the presented study, different sensors were combined with RFID transponders and embedded in concrete components. T2 - 33rd Danubia - Adria Symposium on Advances in Experimental Mechanics CY - Portorož, Slovenia DA - 20.09.2016 KW - Structure health monitoring KW - Concrete KW - Embedded KW - RFID sensors PY - 2016 SN - 978-961-94081-0-0 SP - 68 EP - 69 CY - Ljubljana AN - OPUS4-37535 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bartholmai, Matthias A1 - Strangfeld, Christoph T1 - RFID sensor systems embedded in concrete – systematical investigation of the transmission characteristics N2 - Long-term completely embedded sensor systems offer innovative possibilities for structural health Monitoring of concrete structures. Measuring of relevant parameters, e.g., temperature, humidity, or indication of corrosion can be performed with low energy sensors. This allows to implement passive RFID sensor systems without cable connection and battery, which are power supplied exclusively by the electromagnetic field from the external Reader device. To evaluate characteristics and conditions of this concept, a systematical Investigation of the transmission characteristics with variation of relevant parameters, as communication frequency, installation depth, type of concrete, moisture content, etc. is currently carried out in an interdisciplinary research project at BAM. First results are presented in this paper. T2 - 8th European Workshop On Structural Health Monitoring CY - Bilbao, Spain DA - 05.07.2016 KW - Embedded sensor KW - Energy harvesting KW - Wireless sensors KW - RFID sensors KW - Transmission characteristics KW - Structural health monitoring PY - 2016 AN - OPUS4-37130 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture testing and mapping N2 - Presentation of the Non-destructive testing and evaluation advanced training workshop of division 8.2 regarding moisture measurements. T2 - NDT&E Advanced Training Workshop CY - Berlin, Germany DA - 21.06.2023 KW - Material moisture KW - Moisture transport KW - Building materials KW - Concrete KW - Moisture measurement techniques PY - 2023 AN - OPUS4-57799 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bartholmai, Matthias A1 - Strangfeld, Christoph A1 - Van Bocxlaer, A. T1 - RFID-Sensor-Transponder in Beton N2 - Sensor-Transponder-Lösung der BAM ermöglicht automatisiertes Brückenmonitoring und Predictive Maintenance und detektiert Korrosion in Beton. KW - RFID-Sensorsysteme KW - Bauteilintegrierte Sensoren KW - Betonkorrosion KW - Structural health monitoring PY - 2017 SN - 1860-5907 VL - 2017 IS - 5 SP - 46 EP - 49 PB - Verlag & Freie Medien, Lüneburg CY - Lüneburg AN - OPUS4-40873 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture testing and mapping N2 - Eight different screed types are tested including two different sample heights of 35 and 70 mm. The moisture of the four cement based and four sulphate based screeds are monitored during hydration and evaporation. All samples are stored in a climatic chamber at 23° C and 50 % relative humidity. Embedded sensors like temperature arrays, humidity sensor arrays, and multi-ring electrodes are embedded in the samples to yield a detailed moisture evolution with high depth resolution. Furthermore, nuclear magnetic resonance is used to quantify the water content at different depths. This multi-sensor approach allows a comprehensive monitoring of the moisture and its gradient in the different screed samples. This yields a deeper insight into the hydration, moisture convection, and diffusion processes. T2 - 4. Autumn School - Moisture measurements in porous mineral materials CY - Karlsruhe, Germany DA - 18.09.2017 KW - Material moisture KW - Moisture measurements KW - Corresponding relative humidity KW - Sorption isotherme KW - Porous materials PY - 2017 AN - OPUS4-42096 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture testing and mapping N2 - Most building materials are porous and hydrophilic. Thus, for condition assessment and damage detection a determination of the material moisture is required. In this lecture, a short overview is given regarding moisture transport in porous media in the hygroscopic range. Then, several non-destructive measurement techniques are introduced. Here, the focus lies on their practical application and limitations. T2 - NDT&E Advanced Training Workshop CY - Berlin, Germany DA - 03.07.2024 KW - Building materials KW - Concrete KW - Material moisture KW - Moisture measurement techniques KW - Moisture transport PY - 2024 AN - OPUS4-60605 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - A brief introduction to wind turbine aerodynamics N2 - In general, wind turbines transform the kinetic energy of the wind into electric power. Thereby, the wind turbine blades are facing unsteady loads which are transferred to the hub to generate a rotation of the turbine’s axis. This brief introduction focuses on the aerodynamics of the blades and the corresponding loads. Starting with the basic flow field and loads of an airfoil, terms like stagnation point, boundary layer, Reynolds number, transition, and separation are introduced. For different geometries, lift and drag coefficient curves are discussed. Then, full wings will be considered, including their three-dimensional flow field due to wing tip vortices and crossflows. As a main source of increased loads, unsteady effects are explained in more detail such as gusts, tower passing, earth boundary layer crossing, free stream turbulences, yaw misalignment, etc. At the end, extra loads due to an oscillating free stream are introduced. T2 - QI-Digital: KI-Machbarkeitsstudie Thermografie Rotorblätter CY - Berlin, Germany DA - 13.12.2022 KW - Wind turbine KW - Nondestructive testing KW - Aerodynamics KW - Dynamic stall PY - 2022 AN - OPUS4-56728 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture diffusion affected by the Knudsen effect in temporal changing pore networks N2 - Almost all building materials in civil engineering have an open porosity and interact with or are affected by the environmental conditions. Structures might suffer from effects such as moisture adsorption, carbonation, corrosion, penetration of salt ions and chemical substances, etc. In the hygroscopic range, these processes are mostly driven by diffusion. Due to the confinement of small pores ( 1 m), the Knudsen effect reduces the molecular diffusion. This reduction can become more significant in case of temporal changing pore systems because of physisorption of water vapor, carbonation, or chemisorption. In this study, unstabilised earth blocks and earth masonry are investigated. In a first step, the pore size distribution of the blocks is measured and sorption isotherms are recorded in experiments. Besides the ordinary physisorption, the involved clay minerals undergo swelling or shrinking due to chemisorption. The following two effects must be considered: first, the reduction of the available pore space by the adsorbed water layer. For this, the Hillerborg sorption theory is used, which is a combination of the well-known Brunauer-Emmett-Teller sorption theory and the Kelvin equation. This allows the computation of adsorbed water layers even in curved pore geometries. Second, the variation of the initial pore size distribution due to chemisorption needs to be modelled. Based on these two models, the effective diffusion coefficient can be predicted. For validation, arrays of relative humidity sensors were embedded into a free-standing earth masonry wall. This monitoring was carried out over more than a year to have a broad variety of environmental conditions and was located in Berlin, Germany. The prediction of the effective diffusion coefficient can also be transferred to other processes and allows the investigation of materials having temporarily changing pore systems. Examples are the carbonation of cementitious materials, alkali silica reaction, calcium leaching of long-lasting structures, etc. This effect becomes most prominent in the meso-pore range and might alter the effective diffusion coefficient by more than 100 %. T2 - 4th International Congress on Materials & Structural Stability CY - Rabat, Morocco DA - 08.03.2023 KW - Earth masonry KW - Material moisture KW - Molecular diffusion KW - Chemisoprtion KW - Knudsen effect KW - Physisorption PY - 2023 AN - OPUS4-57140 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Rissdetektion Spannbetonschwellen - Meilensteinpräsentation AP C.1 N2 - Vorhaben 8082: Spannbetonschwellen sollen mit Hilfe von akustischen Verfahren untersucht und der Zustand abgeleitet werden. Die Ergebnisse von Los C- Arbeitspaket 1 werden dem Deutschen Zentrum für Schienenforschung und Siemens Mobility vorgestellt. T2 - DZSF - Rissdetektion Spannbetonschwellen - Meilensteinpräsentation Arbeitspakete B.1 und C.1 CY - Dresden, Germany DA - 23.04.2024 KW - Spannbetonschwellen KW - Zerstörungsfreie Prüfung KW - Akustische Verfahren KW - Zustandsermittlung PY - 2024 AN - OPUS4-59927 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Zustandsermittlung von Spannbetonschwellen N2 - -Über 80 Mio. Schwellen im deutschen Schienennetz verbaut -Lebensdauer einer Schwelle beträgt ca. 20 bis 50 Jahre -Über 2 Mio. Schwellen werden jährlich ausgetauscht, obwohl die Mehrzahl noch intakt ist -Zustandsbewertung mittels ZfP kann Ausschuss verringern -Schadhafte Schwellen könnten mittels ZfP frühzeitig im Gleis erkannt werden, um Gefahren und Unfälle abzuwenden T2 - DZSF - Rissdetektion Spannbetonschwellen - Meilensteinpräsentation Arbeitspakete B.1 und C.1 CY - Dresden, Germany DA - 23.04.2024 KW - Spannbetonschwellen KW - Zerstörungsfreie Prüfung KW - Ultraschallverfahren KW - Zustandsermittlung PY - 2024 AN - OPUS4-59928 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Johann, Sergej A1 - Stührenberg, Jan A1 - Tandon, Aditya A1 - Dragos, Kosmas A1 - Bartholmai, Matthias A1 - Strangfeld, Christoph A1 - Smarsly, Kay T1 - Implementation and validation of robot-enabled embedded sensors for structural health monitoring N2 - In the past decades, structural health monitoring (SHM) has matured into a viable supplement to regular inspections, facilitating the execution of repair and maintenance work in the early stages of structural damage. With the advent of wireless technologies and advancements in information and communication technologies, civil infrastructure has been increasingly instrumented with wireless sensor nodes to record, analyze, and communicate data relevant to SHM. A promising method for SHM is to embed sensors directly into concrete for recording SHM data from inside structural elements. In this paper, a sensor system for embedment into concrete is proposed, able to assess SHM data recorded from concrete. Power is supplied to the sensors on-demand by quadruped robots, which also collect the SHM data via radio-frequency identification (RFID), providing an automated and efficient SHM process. In laboratory experiments, the capability of the sensor system of automatically collecting the SHM data using quadruped robots is validated. In summary, the integration of RFID technology and robot-based inspection presented in this study demonstrates a vital approach to evolve current SHM practices towards more digitalized and automated SHM. T2 - 11th European Workshop On Structural Health Monitoring CY - Potsdam, Germany DA - 10.06.2024 KW - Structural health monitoring KW - RFID-based sensors KW - Smart sensors KW - Embedded sensors KW - Legged robots KW - Quadruped robots PY - 2024 SP - 1 EP - 8 AN - OPUS4-60335 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Hindersmann, I. A1 - Niederleithinger, Ernst T1 - Smart Bridge The duraBASt test bridge equipped with RFID-based sensors N2 - The duraBASt area at the highway intersection “Köln-Ost” is a large test field for road testing. It includes the duraBASt test bridge which is approximately 66 m long and 14.25 m broad. This bridge is part of the “road in the 21st Century” project and is equipped with several sensors for structural health monitoring. This feasibility study is carried out to investigate the prerequisites necessary for the constraction of intelligent bridges in the foture. Embedded sensors are able to measure quantities such as temperature, strain, moisture, corrosion, etc. In the presented work, the focus is set on passive RFID-based sensors. The communication and energy supply are realised by a mobile transmitter through the concrete cover. Hence, no cables or batteries are required. The sensors are designed to withstand the alkaline environment in concrete. Thus, moisture and corrosion values are measurable for several decades. T2 - 10th International Conference on Bridge Maintenance, Safety and Management CY - Online meeting DA - 11.04.2021 KW - RFID based sensors KW - Embedded sensors KW - Bridge Monitoring PY - 2021 DO - https://doi.org/10.1201/9780429279119-321 VL - 2021 SP - 2353 EP - 2358 PB - Taylor & Francis Group CY - London AN - OPUS4-53816 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Ringeloth, David T1 - Rissdetektion an Spannbetonschwellen - Abschlusspräsentation Los C N2 - Dieser Bericht fasst die zentralen Ergebnisse eines 18-monatigen Forschungspro-jekts zusammen, das sich mit der Entwicklung und Bewertung akustischer Verfahren zur zerstörungsfreien Prüfung von Spannbetonschwellen beschäftigt. Die Laborun-tersuchungen wurden an der Bundesanstalt für Materialforschung und -prüfung durchgeführt. Entsprechend der Struktur der definierten Arbeitspakete gliedert sich der Bericht in drei thematische Abschnitte: Zunächst wird der aktuelle Stand der Technik anhand einer umfassenden Literaturrecherche dargestellt, wobei eine Be-wertung der verschiedenen Methoden und Verfahren vorgenommen wurde. Dann erfolgt die Beschreibung der umfangreichen Messungen im Labor. Abschließend werden praxisorientierte Konzepte vorgestellt, wie sich die vielversprechendsten Ansätze auf einer Draisine implementieren lassen, um eine mobile und effiziente Prüfung im realen Einsatz zu ermöglichen. T2 - Abschlusspräsentation zum DZSF-Projekt: Technische Machbarkeitsstudie zur Rissdetektion an Eisenbahn-Spannbetonschwellen mit Methoden der zerstörungsfreien Prüfung CY - Berlin, Germany DA - 16.06.2025 KW - Spannbetonschwelle KW - Rissdetektion KW - Ultraschallverfahren KW - Luftgekoppeltes Impakt-Echo PY - 2025 AN - OPUS4-63545 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - DGZFP Arbeitskreis Dresden Rissdetektion an Spannbetonschwellen N2 - Dieser Bericht fasst die zentralen Ergebnisse eines 18-monatigen Forschungsprojekts zusammen, das sich mit der Entwicklung und Bewertung akustischer Verfahren zur zerstörungsfreien Prüfung von Spannbetonschwellen beschäftigt. Die Laboruntersuchungen wurden an der Bundesanstalt für Materialforschung und -prüfung durchgeführt. Entsprechend der Struktur der definierten Arbeitspakete gliedert sich der Bericht in drei thematische Abschnitte: Zunächst wird der aktuelle Stand der Technik anhand einer umfassenden Literaturrecherche dargestellt, wobei eine Bewertung der verschiedenen Methoden und Verfahren vorgenommen wurde. Dann erfolgt die Beschreibung der umfangreichen Messungen im Labor. Abschließend werden praxisorientierte Konzepte vorgestellt, wie sich die vielversprechendsten Ansätze auf einer Draisine implementieren lassen, um eine mobile und effiziente Prüfung im realen Einsatz zu ermöglichen. T2 - Ergebnisse einer Machtbarkeitsstudie zur zerstörungsfreien Prüfung auf verdeckte Risse an Spannbetonschwellen CY - Dresden, Germany DA - 18.06.2025 KW - Spannbetonschwelle KW - Rissdetektion KW - Ultraschallverfahren KW - Luftgekoppeltes Impakt-Echo PY - 2025 AN - OPUS4-63547 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Ringeloth, David T1 - Rissdetektion an Spannbetonschwellen - Vorführung Los C N2 - Dieser Bericht fasst die zentralen Ergebnisse eines 18-monatigen Forschungsprojekts zusammen, das sich mit der Entwicklung und Bewertung akustischer Verfahren zur zerstörungsfreien Prüfung von Spannbetonschwellen beschäftigt. Die Laboruntersuchungen wurden an der Bundesanstalt für Materialforschung und -prüfung durchgeführt. Entsprechend der Struktur der definierten Arbeitspakete gliedert sich der Bericht in drei thematische Abschnitte: Zunächst wird der aktuelle Stand der Technik anhand einer umfassenden Literaturrecherche dargestellt, wobei eine Bewertung der verschiedenen Methoden und Verfahren vorgenommen wurde. Dann erfolgt die Beschreibung der umfangreichen Messungen im Labor. Abschließend werden praxisorientierte Konzepte vorgestellt, wie sich die vielversprechendsten Ansätze auf einer Draisine implementieren lassen, um eine mobile und effiziente Prüfung im realen Einsatz zu ermöglichen. T2 - Abschlusspräsentation zum DZSF-Projekt: Technische Machbarkeitsstudiezur Rissdetektion an Eisenbahn-Spannbetonschwellen mit Methoden derzerstörungsfreien Prüfung CY - Berlin, Germany DA - 16.06.2025 KW - Spannbetonschwelle KW - Rissdetektion KW - Ultraschallverfahren KW - Luftgekoppeltes Impakt-Echo PY - 2025 AN - OPUS4-63546 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Moisture testing and mapping N2 - Most building materials are porous and hydrophilic. Thus, for condition assessment and damage detection a determination of the material moisture is required. In this lecture, a short overview is given regarding moisture transport in porous media in the hygroscopic range. Then, several non-destructive measurement techniques are introduced. Here, the focus lies on their practical application and limitations. T2 - NDT&E Advanced Training Workshop CY - Berlin, Germany DA - 25.06.2025 KW - Building materials KW - Concrete KW - Material moisture KW - Moisture measurement techniques KW - Moisture transport PY - 2025 AN - OPUS4-63608 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Jeyifous, Olubunmi Anthony A1 - Schönsee, Eric A1 - Strangfeld, Christoph A1 - Hüsken, Götz T1 - Investigating the impact of material rheology on geometric accuracy in 3D concrete printing using real-time monitoring N2 - Additive manufacturing of concrete structures is an innovative and rapidly advancing technology. One of its key advantages is the ability to achieve freeform designs in civil engineering, enabling entirely new architectural possibilities. However, despite the demonstrated benefits of this technology, maintaining consistent print quality during the printing process remains a significant challenge and is seldom implemented. The continuous mixing process inherent in 3D concrete printing introduces potential variations in the dry mix composition or water content, making a single test sample insufficient to represent the entire structure. Moreover, defects in a single layer can compromise the integrity of the whole structure. This underscores the need for continuous, real-time monitoring to document and ensure the quality of the printing process. At the Bundesanstalt für Materialforschung und prüfung (BAM), a 3D concrete printer was developed to enable real-time non-destructive monitoring of material properties during the printing process. This study examines the impact of rheological variations, influenced by water content variations, on the geometric characteristics of printed elements. Geometric measurements are captured in real time using a high-precision laser scanner. Concrete elements are printed under controlled conditions with systematically varied process parameters. Preliminary results reveal a strong correlation between rheological behaviour and the geometric properties of the printed components. T2 - NDT-CE 2025 - The International Symposium on Nondestructive Testing in Civil Engineering CY - Izmir, Turkiye DA - 24.09.2025 KW - 3D concrete printing KW - Real-time monitoring KW - Quality control PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-645394 DO - https://doi.org/10.58286/31704 SN - 1435-4934 SP - 1 EP - 10 PB - NDT.net AN - OPUS4-64539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönsee, Eric A1 - Hüsken, Götz A1 - Kocherla, Amarteja A1 - Strangfeld, Christoph T1 - A framework for characterising the reflection intensity of a 3D-CP mortar N2 - The growing interest of 3D Concrete Printing (3DCP) arises new challenges for quality control. A major challenge lies in evaluation of the interlayer bond strength. An optical approach is developed to monitor the surface properties of the printed layer. Commercial laser profile scanners are utilised to record the reflection intensity of the mortar’s surface. To be applicable in the printing process, the reflection intensity needs to be characterised for each material within the printable region and further effects, like geometry and environmental light, need to be considered. The presented work aims to provide a framework for implementing the laser reflection intensity to 3DCP monitoring. T2 - NDT-CE 2025 - The International Symposium on Nondestructive Testing in Civil Engineering CY - Izmir, Türkiye DA - 24.09.2025 KW - 3D Concrete Printing KW - In Situ Measurements KW - Laser reflection intensity PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-643047 DO - https://doi.org/10.58286/31728 SN - 1435-4934 SP - 1 EP - 4 PB - NDT.net AN - OPUS4-64304 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Strangfeld, Christoph A1 - Maack, Stefan T1 - Grundlagenuntersuchungen zur Anregung von niederfrequentem Ultraschall mit fluidischen Bauteilen N2 - Die zerstörungsfreie Prüfung (ZFP) mittels Ultraschalls wird häufig im Bauwesen eingesetzt, um innere Defekte in Betonstrukturen zu erkennen. Dabei werden Ultraschallwellen im Frequenzbereich von 50 bis 200 kHz genutzt, um Schäden zu entdecken, ohne das Material zu beschädigen. Die meisten derzeit verwendeten Geräte müssen direkten Kontakt mit der Oberfläche haben, was bei großen Bauwerken sehr zeitaufwendig und umständlich ist. Deshalb wird nach alternativen Lösungen gesucht, wie zum Beispiel die luftgekoppelte Ultraschalltechnik, bei der Luft als Übertragungsmedium dient. Solche Geräte könnten die Messzeit um das 50- bis 100-fache verkürzen, was die Inspektion ganzer Strukturen wie Tunnel oder Brücken ermöglichen würde. Dies würde eine zuverlässige Bewertung des Zustands der Infra-struktur erleichtern. Allerdings führt die große Impedanzdifferenz zwischen dem Transducer und der Luft zu erheblichen Energieverlusten, was die Signalstärke schwächt. Geräte, die auf dünnen Membranen oder laserinduzierter Signalanregung basieren, sind oft nicht robust genug für den rauen Baustellenbetrieb. Eine potentielle Lösung sind sogenannte fluidische Oszillatoren, die in der Strömungskontrolle sowie beim Kühlen und Mischen von Flüssigkeiten eingesetzt werden. Sie erzeugen komplett ohne bewegliche Teile schwingende Strömungen, indem sie selbstangeregte Strömungsinstabilitäten nutzen, bei denen der Freistrahl zwischen zwei Kammerwänden durch Feedback-Kanäle hin und her schwingt. Dabei entstehen zeitlich und räumlich schwingende Strömungen am Ausgang. Kleinere Oszillatoren können höhere Frequenzen bis zu 50 kHz erzeugen. Die Frequenz lässt sich durch den Versorgungsdruck steuern, entweder direkt oder über ein Ventil, was die Erzeugung von frequenzmodulierten Signalen ermöglicht. Solche Geräte könnten bei der Untersuchung von Betonelementen eingesetzt werden, um die Dicke und innere Delaminationen zu bestimmen. Die Düsen sind klein, robust und können aus Keramik oder Stahl gefertigt werden, was sie ideal für den Einsatz auf der Baustelle macht. Im Rahmen dieses Projekts wurden fluidische Oszillatoren an der BAM entwickelt, hergestellt und getestet. Dabei wurden die Frequenzinhalte, die Frequenzbandbreite und die Schalldruckamplitude experimentell untersucht. Akustische Messungen mit Mikrophonen sowie erste Tests an Betonproben wurden durchgeführt. Die Düsen wurden geometrisch skaliert, um die Mittenfrequenz und die Schalldruckamplitude zu optimieren. Mit Hilfe von hochfrequenten Druckregeln konnten frequenzmodulierte Anregungssignale (Chirps) erzeugt werden. Die momentan erreichte Frequenzbandbreite von ca. 10 % stellte sich als zu gering heraus für reproduzierbare und statistisch abgesicherte Ultraschall-Messungen durch Beton. KW - Luftgekoppelter Ultraschall KW - Fluidischer Oszillator KW - Verkehrsinfrastruktur PY - 2025 SP - 1 EP - 10 AN - OPUS4-65346 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönsee, Eric A1 - Hüsken, Götz A1 - Jeyifous, Olubunmi Anthony A1 - Mezhov, Alexander A1 - Strangfeld, Christoph T1 - Calculating rheological properties of fresh mortar for additive manufacturing based on experimental, multi-sensor data N2 - Additive manufacturing of concrete structures is a novel and emerging technology. Freecontouring in civil engineering, which allows for entirely new designs, is a significant advantage. Inthe future, lower construction costs are expected with increased construction speeds and decreasingrequired materials and workers. However, architects and civil engineers rely on a certain quality ofexecution to fulfil construction standards. Although several techniques and approaches demonstratethe advantages, quality control during printing is highly challenging and rarely applied. Due to thecontinuous mixing process commonly used in 3D concrete printing, it is impossible to exclude varia-tions in the dry mixture or water content, and a test sample cannot be taken as a representative samplefor the whole structure. Although mortar properties vary only locally, a defect in one layer duringprinting could affect the entire integrity of the whole structure . Therefore, real-time process monitor-ing is required to record and document the printing process.At the Bundesanstalt für Materialforschung und -prüfung (BAM) a new test rig for the additive man-ufacturing of concrete is built. The primary purpose is measuring and monitoring the properties of amortar during the printing process.The following study investigates an approach for calculating yield stress and plastic viscosity based onexperimentally recorded pressure data. The calculations assume that fresh mortar behaves as a Bing-ham fluid and that the Buckingham-Reiner-equation is applicable. A test setup consisting of rigid pipeswith integrated pressure sensors at different positions is utilized.Monitoring the printing process with different sensors is crucial for the quality control of an ongoingprocess. T2 - Non-Traditional Cement and Concrete 2023 Conference CY - Brno, Czech Republic DA - 25.06.2023 KW - 3DCP KW - Monitoring KW - Additive manufacturing KW - Rheology KW - Bingham fluid KW - Concrete printing PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598179 DO - https://doi.org/10.4028/p-EV4gPv SN - 1662-0356 VL - 145 SP - 131 EP - 139 PB - Trans Tech Publications CY - Baech AN - OPUS4-59817 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Strangfeld, Christoph A1 - Prinz, Carsten A1 - Hase, F. A1 - Kruschwitz, Sabine T1 - Data of embedded humidity sensors, sample weights, and measured pore volume distribution for eight screed types N2 - Four cement-based and four calcium-sulphate-based screed types are investigated. The samples have a diameter of 300 mm and a height of 35 or 70 mm. Up to ten humidity sensors are embedded directly during the concreting of the screed samples. Thus, the humidity over the sample height is monitored during hardening, hydration, evaporation, and oven drying. Furthermore, the screed samples are weighted during every measurement to determine the total mass and the corresponding moisture loss. To define the pore system precisely, mercury intrusion porosimetry as well as gas adsorption is performed. According to the data, the entire pore volume distribution is known. The measured pore diameters range from 0.8 nm to 100 μm and the total porosity of the examined screeds ranges between 11 % and 22 %. Based on these measurement data, moisture transport, pore saturation as well as sorption isotherms and their hysteresis may be calculated quantitatively as described by Strangfeld et al. KW - Concrete and screed KW - Material moisture KW - Pore volume distribution KW - Embedded humidity sensors KW - Data in brief PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-448261 UR - https://data.4tu.nl/repository/uuid:d2ba436f-78c0-4105-8a1f-5422fcb37851 DO - https://doi.org/10.4121/uuid:d2ba436f-78c0-4105-8a1f-5422fcb37851 SP - 1 EP - 4 PB - 4TU.Centre for Research Data CY - Delft AN - OPUS4-44826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Prinz, Carsten A1 - Hase, Felix A1 - Kruschwitz, Sabine T1 - Data of embedded humidity sensors, sample weights, and measured pore volume distribution for eight screed types N2 - Four cement-based and four calcium-sulphate-based screed types are investigated. The samples have a diameter of 300 mm and a height of 35 or 70 mm. Up to ten humidity sensors are embedded directly during the concreting of the screed samples. Thus, the humidity over the sample height is monitored during hardening, hydration, evaporation, and oven drying. Furthermore, the screed samples are weighed during every measurement to determine the total mass and the corresponding moisture loss. To define the pore system precisely, mercury intrusion porosimetry as well as gas adsorption is performed. According to the data, the entire pore volume distribution is known. The measured pore diameters range from 0.8 nm to 100 µm and the total porosity of the examined screeds ranges between 11% and 22%. Based on these measurement data, moisture transport, pore saturation as well as sorption isotherms and their hysteresis may be calculated quantitatively as described in “Monitoring of the absolute water content in porous materials based on embedded humidity sensors” (Strangfeld and Kruschwitz, 1921). KW - Concrete and screed KW - Embedded humidity sensors KW - Pore volume distribution KW - Material moisture PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-462339 DO - https://doi.org/10.1016/j.dib.2018.09.020 SN - 2352-3409 VL - 21 SP - 8 EP - 12 PB - Elsevier CY - Amsterdam AN - OPUS4-46233 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst A1 - Maak, Stefan A1 - Mielentz, Frank A1 - Effner, Ute A1 - Strangfeld, Christoph A1 - Timofeev, Juri T1 - Review of recent developments in ultrasonic echo testing of concrete N2 - Ultrasonic methods are used in concrete investigations since decades. While being limited to transmission testing in the laboratory for a while, in-situ echo measurements for structural investigations and condition assessment have made their way into practical application in the past 20 years. However, several challenges remain. On one side, there are technical issues as limitations in depth of penetration, resolution and imaging capabilities. On the other side there are still gaps in validation, standardization and certification, which are limiting the applicability in condition/load capacity assessment. This review reports a couple of developments which will help to overcome these issues. This includes technical developments as new devices which are easier to handle on site or giving a much deeper penetration depth (e.g. the LAUS device at BAM) as well as improvements in imaging by hardware update (e. g. air coupled ultrasound or coded signals) or new software (e. g. RTM imaging). To foster the application in real world projects we are as well working on standardization by developing new reference specimen with international partners which will ensure world-wide comparability of ultrasonic and other methods and quality assurance codes. Further, non-destructive methods are being used to update probabilistic models used for the reassessment of existing structures to support the structural engineer’s decisions. T2 - SMAR 2019 CY - Potsdam, Germany DA - 27.08.2019 KW - Engineered Barrier System (EBS) KW - Ultraschall KW - NDT KW - Re-assessment of exiting bridges PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-489686 SP - 1 EP - 6 AN - OPUS4-48968 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Neumann, Patrick P. T1 - Informations-Austausch zu mobilen autonomen Roboterplattformen N2 - Abteilungsübergreifender Informations-Austausch zu mobilen autonomen Roboterplattformen T2 - Informations-Austausch zu mobile autonomen Roboterplattformen CY - BAM, Berlin, Germany DA - 01.03.2019 KW - Mobile Plattform KW - Roboter KW - Autonome Systeme PY - 2019 AN - OPUS4-47475 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Water content in construction materials N2 - Discussion of material moisture and moisture transport in liquid and vapour phase. Prediction of the pore saturation in partially saturated pores in building materials. T2 - 5. Herbstschule Competence Center for Material Moisture CY - Ettlingen, Germany DA - 08.10.2019 KW - Material moisture KW - Building materials KW - Embedded sensors KW - Partially saturated pores PY - 2019 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. AN - OPUS4-49260 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin A1 - Strangfeld, Christoph A1 - Maack, Stefan T1 - Entwicklung eines luftgekoppelten Ultraschall-Echo-Prüfverfahrens mittels fluidischer Anregung N2 - In vielen technischen Bereichen werden Ultraschallverfahren zur zer-störungsfreien Werkstoffprüfung eingesetzt. Dabei wird ein Schallpuls von einem Prüfkopf in ein Prüfobjekt eingebracht. Der Puls kann unter anderem durch Membra-nen oder Piezoelemente erzeugt werden und wird in der Regel durch direkten Kontakt oder über ein Koppelmittel an das Objekt übertragen. Luftgekoppelter Ultraschall spielt in kommerziellen Anwendungen bisher eine untergeordnete Rolle, da die Dif-ferenz der akustischen Impedanzen von Luft und Festkörpern immense Verluste beim Übergang des Schallsignals hervorruft. In diesem Beitrag soll ein neuartiges Anregungsprinzip vorgestellt werden, mit dem ein Großteil dieser Verluste vermieden wird. Anstelle eines Festkörpers soll mit Hilfe einer fluidischen Düse Druckluft zur Signalerzeugung eingesetzt werden. In die-ser Düse wird eine selbsterhaltende Strömungsinstabilität erzeugt, die einen Schall-puls von bis zu 100 kHz hervorruft, sodass der Impedanzverlust in die Umgebungsluft entfällt. Da die charakteristische Frequenz eines fluidisch generierten Pulses maßgeb-lich von der Bauform der Düse und dem anliegenden Druck abhängt, lässt sich mittels einer geeigneten Strömungsregelung ein breiter Frequenzbereich zur Abtastung nut-zen. Die so emittierten Pulse werden auf das Prüfobjekt gerichtet und die reflektierten Signale mit einem Laservibrometer an der Oberfläche des Objekts im Echo-Verfahren abgetastet. Von drei signalmindernden Materialübergängen bei gewöhnlichem luftge-koppeltem Ultraschall bleibt in dem hier vorgeschlagenen Messystem lediglich die Grenzfläche von Luft zu Prüfkörper, sodass eine höhere Signalausbeute als bisher er-wartet werden kann. T2 - DACH-Jahrestagung 2019 CY - Friedrichshafen, Germany DA - 27.05.2019 KW - Ultraschall KW - Ultrasound KW - Air-coupled KW - Luftgekoppelt KW - Fluidic oscillator KW - Fluidischer Oszillator KW - Laser-Doppler-Vibrometer KW - Refraktovibrometrie KW - Refracto-vibrometry KW - NDT KW - ZfP PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-481207 VL - 2019 SP - 1 EP - 8 PB - DGZfP Deutsche Gesellschaft für Zerstörungsfreie Prüfung AN - OPUS4-48120 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Johann, Sergej A1 - Strangfeld, Christoph A1 - Müller, Maximilian A1 - Mieller, Björn A1 - Bartholmai, Matthias T1 - RFID sensor systems embedded in concrete – validation experiments for long-term monitoring N2 - Structural Health Monitoring (SHM) is an important part of buildings surveillance and maintenance to detect material failure as early as possible and to contribute in protection of structures and their users. The implementation of Radio Frequency Identification (RFID) sensor systems without cable connection and battery into building components offers innovative possibilities to enable long-term in-situ SHM of addressed structures, bridges. The objectives of the presented study are complete embedding of RFID sensors systems in concrete, full passive communication with the systems, at best for the whole life span of structures. One challenge for this task is the highly alkaline environment in concrete, which requires non-degrading and robust encapsulation. Further Requirements are passive communication and energy supply, appropriate antenna design, placement and fixation in concrete, and the selection and implementation of sensors and connections. The concept is to develop and optimize a simple and robust system, which meets the requirements, as well as comprehensive validation in concrete specimen and real world applications. Two different systems were developed (HF and UHF RFID, respectively). First tasks were the implementation of analog sensors using the superposition principle for the signal adaption. Investigation of suitable materials for robust encapsulation and sensor protection against basic environments. Four materials were investigated in pH 13 solution for 14 days - 3D-Printer-Polymer was completely resolved - PVC has no noticeable decrease in weight - (VitaPro) glass filter for the sensor protector, has weight loss 2.7 % - The epoxy resin has increased by 1.8 % due to moisture expansion Different concrete samples were prepared for the validation of the systems. RFID sensors were embedded in different integration depths. Investigate the energy- and data transfer through concrete, also with varying moisture content. Additionally, signal strength data was used to optimize and validate the antenna characteristics in concrete. Next steps are to guarantee a sufficient energy supply for UHF RFID systems embedded in different concrete mixtures and further embedding the HF and UHF RFID systems in real bridges and buildings to validate the long term monitoring. T2 - DGZfP-Jahrestagung 2017 CY - Koblenz, Germany DA - 22.05.2017 KW - Smart structures KW - RFID sensors KW - Long-term requirements KW - Structural health monitoring KW - Passive RFID KW - Sensor requirements KW - Sensors in concrete PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-403496 UR - https://www.ndt.net/?id=21499 SN - 1435-4934 VL - 22 IS - 9 SP - 1 EP - 7 PB - NDT.net CY - Kirchwald AN - OPUS4-40349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Johann, Sergej A1 - Strangfeld, Christoph A1 - Müller, Maximilian A1 - Mieller, Björn A1 - Bartholmai, Matthias T1 - RFID sensor systems embedded in concrete – Validation experiments for long-term monitoring T1 - RFID Sensorsysteme eingebettet in Beton – Validierungsexperimente zum Langzeitmonitoring N2 - Structural Health Monitoring (SHM) is an important part of buildings surveillance and maintenance to detect material failure as early as possible and to contribute in protection of structures and their users. The implementation of Radio Frequency Identification (RFID) sensor systems without cable connection and battery into building components offers innovative possibilities to enable long-term in-situ SHM of addressed structures, bridges. The objectives of the presented study are complete embedding of RFID sensors systems in concrete, full passive communication with the systems, at best for the whole life span of structures. One challenge for this task is the highly alkaline environment in concrete, which requires non-degrading and robust encapsulation. Further Requirements are passive communication and energy supply, appropriate antenna design, placement and fixation in concrete, and the selection and implementation of sensors and connections. The concept is to develop and optimize a simple and robust system, which meets the requirements, as well as comprehensive validation in concrete specimen and real world applications. Two different systems were developed (HF and UHF RFID, respectively). First tasks were the implementation of analog sensors using the superposition principle for the signal adaption. Investigation of suitable materials for robust encapsulation and sensor protection against basic environments. Four materials were investigated in pH13 solution for 14 days - 3D-Printer-Polymer was completely resolved - PVC has no noticeable decrease in weight - (VitaPro) glass filter for the sensor protector, has weight loss 2.7% - The epoxy resin has increased by 1.8% due to moisture expansion Different concrete samples were prepared for the validation of the systems. RFID sensors were embedded in different integration depths. Investigate the energy- and data transfer through concrete, also with varying moisture content. Additionally, signal strength data was used to optimize and validate the antenna characteristics in concrete. Next steps are to guarantee a sufficient energy supply for UHF RFID systems embedded in different concrete mixtures and further embedding the HF and UHF RFID systems in real bridges and buildings to validate the long term monitoring. KW - RFID sensors KW - Structural health monitoring KW - Sensors in concrete KW - Smart structures KW - Sensor requirements PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-418331 UR - http://www.ndt.net/?id=21499 SN - 1435-4934 VL - 22 IS - 9 SP - Artikel 8, 1 EP - 7 PB - NDT.net CY - Bad Breisig AN - OPUS4-41833 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Johann, Sergej A1 - Bartholmai, Matthias T1 - Smart RFID Sensors Embedded in Building Structures for Early Damage Detection and Long-Term Monitoring N2 - In civil engineering, many structures are made of reinforced concrete. Most Degradation processes relevant to this material, e.g., corrosion, are related to an increased level of material moisture. Therefore, moisture monitoring in reinforced concrete is regarded as a crucial method for structural health monitoring. In this study, passive radio frequency identification (RFID)-based sensors are embedded into the concrete. They are well suited for long-term operation over decades and are well protected against harsh environmental conditions. The energy supply and the data transfer of the humidity sensors are provided by RFID. The sensor casing materials are optimised to withstand the high alkaline environment in concrete, having pH values of more than 12. Membrane materials are also investigated to identify materials capable of enabling water vapour transport from the porous cement matrix to the embedded humidity sensor. By measuring the corresponding relative humidity with embedded passive RFID-based sensors, the cement hydration is monitored for 170 days. Moreover, long-term moisture monitoring is performed for more than 1000 days. The Experiments show that embedded passive RFID-based sensors are highly suitable for long-term structural health monitoring in civil engineering. KW - RFID based sensors KW - Embedded sensors KW - Corresponding relative humidity KW - Porous building materials KW - Reinforced concrete KW - Corrosion KW - Civil engineering PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-500831 DO - https://doi.org/10.3390/s19245514 VL - 19 IS - 24 SP - 1 EP - 18 PB - MDPI CY - Basel, Swiss AN - OPUS4-50083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Correlation between the electric impedance and the water layer thickness in partially saturated screed samples N2 - Discussion of material moisture in liquid and vapour phase. Prediction of the pore saturation in partially saturated pores in building materials. Correlation between the electric impedance and the water layer thickness in partially saturated screed samples. T2 - 10. CMM Tagung CY - Ettlingen, Germany DA - 10.10.2019 KW - Embedded sensors KW - Corresponding relative humidity KW - Electrical impedance KW - Material moisture KW - Building materials KW - Partiallly saturated pores PY - 2019 AN - OPUS4-49261 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -