TY - CONF A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Leinitz, Sarah ED - Diouri, A. ED - Boukhari, A. ED - Ait Brahim, L. ED - Bahi, L. ED - N., Khachani ED - Saadi, M ED - Aride, J. ED - Nounah, A. T1 - Concrete casting robustness improvement due to active rheology N2 - With ongoing innovation in process technology, the challenges of concrete technology are more and more focused on the rheological optimisation for these processes, since improper mixture stability or poor compaction ability negatively affect the concrete homogeneity and quality. However, along with the increasing complexity of today’s concrete mixture compositions, concrete becomes more prone to failure regarding the casting process. Variable properties of the raw materials typically cause changing workability. The reasons can be found among others in scattering water contents, physical or chemical properties of the cement or varying environmental temperatures. Robustness in the delicately adjusted rheology, however, is of utmost importance for modern and future process technology, from sprayed concrete over pumpable concrete towards 3D-printing, with regard to the long-term strength, the function and the durability. Typically, material induced changes cannot be identified easily due to the complex interactions of concrete constituents. Therefore, a precise and prompt counteraction is impossible. However, it is known that the yield stress can be controlled by addition of supplementary superplasticizer or stabilising agent. In combination with computerized process observation tools that can rapidly interpret and react on changes in the rheology, it is therefore thinkable, that only these two admixture types can adjust the rheology steadily and permanently, regardless of the actual root cause for observed macroscopic rheology change. The presentation will firstly give a comprehensive overview of effects at the interface between pore solution, particles and hydrates, which affect the rheology of fresh concrete. Secondly, ways are recommended how the rheology can be actively manipulated before eventually computerized methods are demonstrated that help to actively and rapidly assess and counteract performance scatter during steady casting processes. T2 - 2nd International Congress on Materials & Structural Stability (CMSS-2017) CY - Rabat, Morocco DA - 22.11.2017 KW - Cusum KW - Rheology KW - Control Chart KW - Concrete KW - Robustness PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-444317 DO - https://doi.org/10.1051/matecconf/201814901001 SN - 2261-236X VL - 149 SP - 01001-1 EP - 01001-7 PB - EDP Sciences CY - Les Ulis AN - OPUS4-44431 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Mota Gassó, Berta A1 - Sturm, Heinz A1 - Pauli, Jutta ED - Greim, M. ED - Kusterle, W. ED - Teubert, O. T1 - Influence of effects on nano and micro scale on the rheological performance of cement paste, mortar and concrete N2 - Chemical admixtures like superplasticisers or stabilising agents are of ever increasing importance for modern concrete technology. They liberate the workability of concrete from its dependency on water content, and thus, open the gate towards innovative and future oriented concrete technologies such as self-compacting concrete. Today, admixture addition has become common practice in concrete technology, but the understanding of their highly complex mode of operation is extremely difficult and demands for understanding of processes within the range between nanometres and centimetres. Due to its complex time-dependent, multi-phase and multi-scale behaviour, flowable concrete systems are highly complicated and cannot be described comprehensively by simple models. It is therefore extremely challenging to identify the relevant parameters that predominantly control flow phenomena on different size scales, since these may occur on any scale between the nano scale (e.g. superplasticizer adsorption) and macro scale (e.g. grading of the aggregates). The present study discusses fundamental mechanisms at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation, and links these effects to macroscopic flow phenomena. Methods are discussed that appear promising interdisciplinary tools for enhancement of the understanding of the relevant interactions that are responsible for the macroscopic flow of flowable concrete. T2 - 25. Workshop und Kolloquium Rheologische Messsungen an Baustoffen CY - Regensburg, Germany DA - 02.03.2016 KW - Rheology KW - Cement KW - Concrete KW - Superplasticizer KW - Nano scale PY - 2016 SN - 978-3-7345-1313-8 SP - 294 EP - 307 PB - tredition CY - Hamburg AN - OPUS4-36862 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Ultrasonic methods for quality assurance and condition assessment in nuclear concrete structures – lessons learned N2 - Ultrasonic non-destructive testing methods have found various applications in quality assurance and condition assessment of nuclear concrete structures. This includes but is not limited to the localization of construction features (thickness measurements, reinforcement, tendon ducts, and others) and damage detection (e. g. corrosion or cracks). However, there are still limitations, e. g. limited penetration depth and resolution, issues when testing hybrid steel/concrete structures as well as absence of standards and regulations. This presentation will show progress in some of these issues and will focus on advanced instrumentation and validation of ultrasonic NDT for concrete structures. Ultrasonic echo testing has been limited to a penetration depth of less than one meter in reinforced concrete. The development of the LAUS (Large Aperture Ultrasonic System), using a large array of ultrasonic transducers and wider offsets between transmitter and receiver, allows to reach up to 5 m in reinforced concrete and 9 m in unreinforced concrete. This capability has been demonstrated by collecting data from an engineered salt concrete barrier in an underground nuclear waste storage facility. Due to an increasingly competitive environment, commercial manufacturers will continue to develop equipment with enhanced penetration and/or increased resolution. To quantify the capabilities and reliability of ultrasonic tests, validation mockups with engineered flaws are required. EPRI and BAM have built a large-scale mockup at a test site close to Berlin (BAM-TTS, Horstwalde) using a design which is repeated at other places. This presentation will also cover the methods deployed on engineered flaws and the repeatability of the test results. T2 - NDE in Nuclear CY - Charlotte, NC, USA DA - 25.7.2019 KW - Concrete KW - Nuclear Structures KW - Ultrasound PY - 2019 AN - OPUS4-48690 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Ultrasonic methods for concrete: To boldly see, what we have not seen before N2 - This keynote talk at NDE 2019 discusses specific progress in ultrasonic testing of concrete structures. A deep penetration instrument (LAUS) is introduced as well as advanced imaging methods adopted from geophysics and new approaches to ultrasonic monitoring. T2 - NDE 2019 CY - Bangalore, India DA - 05.12.2019 KW - NDT KW - Concrete KW - Ultrasound KW - Imaging KW - Monitoring PY - 2019 AN - OPUS4-50170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Ultrasonic monitoring of structural concrete elements N2 - Ultrasonic transmission measurements are used to monitor concrete elements mostly on a laboratory scale since decades. Recently, coda wave interferometry, a technique adapted from seismology, has been introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete samples and even large construction elements without having a transducer directly at the location where the change is taking place. The methodology works best with embedded transducers to avoid coupling issues or excessive environmental influence. These transducers can be used for newly built and existing structures. Recently, large concrete beams have been equipped with a network of transducers and loaded until failure. Using code wave interferometry, it was possible to visualize stress fields and damaged areas. This paper gives an overview of the state of the art, recent results achieved at BAM and a task list for further results and development. T2 - International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) CY - Rovinj, Croatia DA - 20.03.2019 KW - Concrete KW - Ultrasound KW - Monitoring KW - coda wave interferometry PY - 2019 AN - OPUS4-47676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst ED - Gabrijel, Ivan ED - Grosse, Christian ED - Skazlić, Marijan T1 - Ultrasonic monitoring of structural concrete elements N2 - Ultrasonic transmission measurements are used to monitor concrete elements mostly on a laboratory scale since decades. Recently, coda wave interferometry, a technique adapted from seismology, has been introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete samples and even large construction elements without having a transducer directly at the location where the change is taking place. The methodology works best with embedded transducers to avoid coupling issues or excessive environmental influence. These transducers can be used for newly built and existing structures. Recently, large concrete beams have been equipped with a network of transducers and loaded until failure. Using code wave interferometry, it was possible to visualize stress fields and damaged areas. This paper gives an overview of the state of the art, recent results achieved at BAM and a task list for further results and development. T2 - International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) CY - Rovinj, Croatia DA - 20.3.2019 KW - Concrete KW - Ultrasound KW - Monitoring KW - coda wave interferometry PY - 2019 SN - 978-2-35158-227-5 SP - 1 EP - 11 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-47677 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd T1 - Fast quantitave chemical analysis of concrete using LIBS N2 - Overview of application of LIBS for the fast and automated quantitative chemical analysis of concrete. T2 - NDT-E Workshop CY - Berlin, Germany DA - 12.06.2019 KW - Sulphate KW - LIBS KW - Concrete KW - Damage KW - Chloride KW - Mapping PY - 2019 AN - OPUS4-51704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst A1 - Wiggenhauser, Herbert T1 - The LAUS: First Applications of a New System for Ultrasonic Imaging of Very Concrete Structures N2 - The LAUS (Large Aperture Ultrasonic System) has been developed to image very thick concrete structures, which are not accessible for commercial systems. The device and the corresponding software is the result of joint Research of BAM, an ultrasonic instrument manufacturer and University of Kassel, Germany. It consists of 12 separate Arrays of 32 point-contact shear wave transducers each, which can be deployed in flexible configurations. Each array is combined with battery and transmitter, receiver and wireless communication electronics. Three case histories are presented. First the system was deployed on a 5-m thick heavily reinforced foundation slab. The reflection of the slab’s bottom was imaged clearly. In addition, a multiple reflection was registered, thus giving hope that even thicker elements might be imaged by the instrument. Second, the LAUS was used to investigate a massive bridge girder where a heavy rainstorm during concreting had led to imperfections that were visible after removing the formwork was removed. The LAUS could image tendon ducts in 1.8m depth and the backwall closely behind them. Some limited areas showed blurred reflections and were checked by drill holes; these areas were affected by diffuse damage which could be repaired by injections. Third, a large retaining wall was checked for thickness. Meanwhile, the LAUS has been used in underground waste deposits (nuclear and other) for quality assurance of sealing plugs. A confirmed penetration depth of about 7 m has been reached. T2 - SMT and NDT-CE 2018 CY - New Brunswick, NJ, USA DA - 27.08.2018 KW - LAUS (Large Apertur Ultrasonic System) KW - Ultrasonic echo KW - Deep penetration KW - Concrete PY - 2019 UR - https://asnt.org/smt18papers SN - 978-1-57117-456-7 VL - 11/19 SP - 208 EP - 213 PB - The American Society for Nondestructive Testing, Inc. CY - Columbus, OH, USA AN - OPUS4-47238 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kruschwitz, Sabine T1 - Ortsaufgelöste NMR-Relaxometrie an mineralischen Baustoffen N2 - Zahlreiche Schädigungsprozesse in Baustoffen stehen im engen Zusammenhang mit Feuchteeintrag und Feuchtetransport. Als Beispiel sind die schädigende Alkali-Kieselsäurereaktion (AKR) von Beton sowie Frost-Tauwechsel induzierte Gefügeschäden genannt. Zur zerstörungsfreien, ortsaufgelösten Feuchtemessung eignet sich die im Bereich der Geophysik etablierte, aber im Bauingenieurwesen noch wenig verbreitete, Messmethode der Nuklear Magnetischen Resonanz (NMR). Unter Verwendung der NMR-Relaxometrie sind sowohl Aussagen zum Feuchtegehalt und dessen räumliche Verteilung als auch die Charakterisierung der Porengrößen möglich, die das Transportverhalten eines porösen Materials maßgeblich beeinflussen. Zur Erfassung der Mikro- und Mesoporen in Baustoffen ist dabei die Auflösung von kurzen T2 Relaxationszeiten unabdingbar. Bisher ist es mit gängigen NMR-Laborgeräten nur begrenzt möglich, solche kurzen T2-Zeiten schichtselektiv zu erfassen. Vor diesem Hintergrund wurde ein speziell für die Messung an mineralischen Baustoffen optimierter NMR-Tomograph beschafft. Dieser ermöglicht sowohl schichtselektive Messungen von Bohrkernen mit Durchmessern von bis zu 70 mm als auch bildgebende Untersuchungen an Proben mit Durchmessern ≤ 40 mm. Erste Untersuchungsergebnisse an Sandstein, Tuffstein und Beton zeigen die Leistungsfähigkeit des neuen NMR-Tomographen zur Erfassung der porengrößenspezifischen Feuchteverteilung. In diesem Beitrag werden erste Ergebnisse verschiedenartiger Laborversuche exemplarisch dargestellt. Für Sandsteine mit unterschiedlichsten Porengrößenverteilungen wurden mit dem neuen NMR-Tomographen und einem herkömmlichen NMR-System vergleichbare T2 Zeitenverteilungen ermittelt. Am sehr heterogenen Tuffstein konnten unterschiedlich poröse (und feuchte) Bereiche räumlich aufgelöst werden. Im Beton ließ sich der Feuchtetransport im Zementstein porengrößenspezifisch, schichtselektiv und zeitlich aufgelöst verfolgen. Die bisher gewonnenen Ergebnisse zeigen das breite Anwendungsspektrum des neuen NMR Tomographen auf und ermöglichen ein besseres Verständnis des Feuchtetransports und der oft damit einhergehenden Schädigungsprozesse in Baustoffen. T2 - 79. Jahrestagung Deutsche Geophysikalische Gesellschaft CY - Brunswick, Germany DA - 04.03.2019 KW - Concrete KW - NMR KW - Sandstone KW - Capillary suction PY - 2019 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. AN - OPUS4-47501 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst A1 - Abraham, Odile A1 - Larose, Eric T1 - A review on ultrasonic monitoring of concrete: coda wave interferometry and beyond N2 - The propagation of ultrasonic waves in concrete is affected by its micro- and macro-structure, geometry and properties as well as external influences as stress, temperature or moisture. In addition, age and degradation have a strong influence. Therefore, Ultrasound has been used to monitor concrete samples and structures since decades. However, early applications using conventional techniques as time-of flight or changes in amplitudes have been limited to detect changes in a late stage close to serviceability or ultimate load states. Around 2000, several new, more sensitive techniques adopted from geophysics or other field of material sciences have been introduced to research in ultrasonic monitoring of concrete. The most discussed methodologies are coda wave interferometry, a technique which allows to detect very subtle changes from repeated ultrasonic measurements. Nonlinear acoustic techniques help to identify e. g. cracks even in an inhomogeneous background. Both techniques can be combined. This paper reviews methods and results achieved so far on the laboratory scale and with full scale models the directions for future research and application is given as well. T2 - QNDE 2019 CY - Portland, OR, USA DA - 14.07.2019 KW - Ultrasound KW - Coda wave interferometry KW - Concrete KW - Nonlinear KW - Monitoring PY - 2019 SP - Paper 1234 AN - OPUS4-48686 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - A review on ultrasonic monitoring of concrete: coda wave interferometry and beyond N2 - The propagation of ultrasonic waves in concrete is affected by its micro- and macro-structure, geometry and properties as well as external influences as stress, temperature or moisture. In addition, age and degradation have a strong influence. Therefore, Ultrasound has been used to monitor concrete samples and structures since decades. However, early applications using conventional techniques as time-of flight or changes in amplitudes have been limited to detect changes in a late stage close to serviceability or ultimate load states. Around 2000, several new, more sensitive techniques adopted from geophysics or other field of material sciences have been introduced to research in ultrasonic monitoring of concrete. The most discussed methodologies are coda wave interferometry, a technique which allows to detect very subtle changes from repeated ultrasonic measurements. Nonlinear acoustic techniques help to identify e. g. cracks even in an inhomogeneous background. Both techniques can be combined. This paper reviews methods and results achieved so far on the laboratory scale and with full scale models the directions for future research and application is given as well. T2 - QNDE 2019 CY - Portland, OR, USA DA - 14.07.2019 KW - Ultrasound KW - Coda wave interferometry KW - Concrete KW - Nonlinear KW - Monitoring PY - 2019 AN - OPUS4-48688 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Abraham, O. A1 - Niederleithinger, Ernst A1 - Chapeleau, X. A1 - Klikowicz, P. A1 - Brühwiler, E. A1 - Bassil, A. A1 - Wang, Xin A1 - Chakraborty, J. A1 - Bayane, I. A1 - Leduc, D. A1 - Salamak, M. A1 - Katunin, A. A1 - Sørensen, J.D. T1 - Addressing the need to monitor concrete fatigue with nondestructive testing: Results of infrastar European project N2 - Fatigue is one of the most prevalent issues, which directly influences the service life expectancy of concrete structures. Fatigue has been investigated for years for steel structures. However, recent findings suggest that concrete structures may also be significantly subjected to fatigue phenomena that could lead to premature failure of certain structural elements. To date, fatigue of reinforced concrete has been given little focus. Knowledge on the influence factors and durability/capacity effects on this material should be improved. Current technological means to measure fatigue in civil structures like bridges and wind turbines (both onshore and offshore) are outdated, imprecise and inappropriate. Meanwhile, this topic has got much more attention as time-variant loading on concrete structures plays an increasing role, e.g. in bridges with increasing traffic and heavier trucks, and for wind turbines for renewable energy production, e.g. for offshore wind turbine support structures affected by wind and waves. The European Innovative Training Networks (ITN) Marie Skłodowska-Curie Actions project INFRASTAR (Innovation and Networking for Fatigue and Reliability Analysis of Structures - Training for Assessment of Risk) provides research training for 12 PhD students. The project aims to improve knowledge for optimizing the design of new structures as well as for more realistic verification of structural safety and more accurate prediction of the remaining fatigue lifetime of existing concrete structures. First, the INFRASTAR research framework is detailed. Then it will be exemplified through the presentation of the major results of the four PhD students involved in the work package dealing with auscultation and monitoring. This includes the development and improvement of Fiber Optics (FO) and Coda Wave Interferometry (CWI) for crack sizing and imagery, new sensor technologies and integration, information management, monitoring strategy for fatigue damage investigation and lifetime prediction. T2 - SMT and NDT-CE 2018 CY - New Brunswick, NJ, USA DA - 27.08.2018 KW - Concrete KW - Fatigue KW - Crack KW - Monitoring KW - Non-destructive testing PY - 2019 UR - https://asnt.org/smt18papers SN - 978-1-57117-456-7 VL - 11/19 SP - 2 EP - 13 PB - The American Society for Nondestructive Testing, Inc. CY - Columbus, OH, USA AN - OPUS4-47237 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Seismic methods to test concrete strcutures N2 - Seismic methods are increasingly used to improve ultrasonic imaging and monitoring of concrete. At BAM, we are research mainly the use of Reverse Time Migration to get better images from ultrasonic echo data of thick, complex concrete structures. Coda wave interferometry is used to detect subtle changes in concrete constructions, e. g. using embedded ultasonic transducers. T2 - Geophysikalisches Seminar der Universität Potsdam CY - Potsdam,. Germany DA - 25.01.2019 KW - Concrete KW - Ultrasound KW - Monitoring KW - Imaging PY - 2019 AN - OPUS4-47302 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd T1 - LIBS for the analysis of concrete N2 - Special features and examples of using LIBS on concrete. T2 - Workshop on tandem LIBS/LA-ICP-MS CY - Berlin, Germany DA - 18.11.2019 KW - Mobile system KW - LIBS KW - Concrete KW - Damage KW - Chloride KW - Sulphate KW - Mapping PY - 2019 AN - OPUS4-51710 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gottlieb, Cassian T1 - Chemometrics for the analysis of cement-based materials N2 - The analysis of the chemical composition of cement-based materials like concrete is a crucial task in civil engineering. Concrete is a multi-phase material made of cement, water, aggregates, additives and admixtures. During the damage assessment of concrete structures, the external ingress of harmful species like chlorine, alkalis or sulfates needs to be determined. In order to provide a fast and precise analysis of concrete the application of LIBS offers unique possibilities as the technique can detect all elements at air atmosphere. To determine the condition of concrete, the information about the chemical composition, the ingress of harmful species as well as the evaluation of characteristic values like the used cement type or the type of aggregates are needed. This work presents the two-dimensional evaluation of concrete samples using LIBS and multivariate data analysis of atomic and molecular emission. For the evaluation of the main components different classification methods will be applied to identify the heterogeneity of the samples. With respect to their specific phase, different species will be quantified using multivariate regression (PLS) and important figures of merit will be presented. All results will be verified using Standard procedure of wet chemistry (XRF, potentiometric titration and ICP-OES). T2 - 10th Euro-Mediterranean Symposium CY - Brno, Czech Republic DA - 08.09.2019 KW - Heterogeneous material KW - Chemometics KW - Cement KW - Concrete PY - 2019 AN - OPUS4-51838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wilsch, Gerd T1 - Mobile LIBS system for evaluation of concrete structures on site N2 - Features and application of a mobile LIBS system for evaluation of concrete structures on-site. T2 - EMSLIBS 2019 CY - Brno, Czech Republic DA - 08.09.2019 KW - On-site KW - LIBS KW - Concrete KW - Mapping KW - Evaluation PY - 2019 AN - OPUS4-51711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Oesch, Tyler A1 - Weise, Frank A1 - Meinel, Dietmar A1 - Gollwitzer, Christian T1 - Quantitative in-situ analysis of water transport in concrete completed using X-ray computed tomography N2 - This paper describes a novel methodology for quantitative in-situ moisture measurement without tracking agents using X-ray computed tomography (XCT). The high levels of grey-scale precision required for the measurement of moisture without tracking agents resulted in the need for an additional image calibration procedure to correct for water-related X-ray scattering and for equipment-variability related artefacts arising during in-situ testing. This calibration procedure was developed on the basis of existing principles of XCT image cor-rection. Resulting images of moisture distribution exhibit a high level of agreement with expected material behaviour. This research demonstrated that XCT can be successfully used to measure both moisture-front movement over time and changes in 3D moisture distribution within samples. This approach to moisture measurement lays the groundwork for the planned future investigation of the interaction between cracking induced by varying chemical and mechanical processes and water transport in concrete. KW - X-ray computed tomography (XCT) KW - In-situ testing KW - Water transport KW - Quantitative moisture measurement KW - Concrete PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474395 DO - https://doi.org/10.1007/s11242-018-1197-9 SN - 1573-1634 VL - 127 IS - 2 SP - 371 EP - 389 PB - Springer Netherlands AN - OPUS4-47439 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shokouhi, Parisa A1 - Zoëga, Andreas A1 - Wiggenhauser, Herbert T1 - Nondestructive investigation of stress-induced damage in concrete N2 - The changes in the sonic surface wave velocity of concrete under stress were investigated in this paper. Surface wave velocities at sonic frequency range were measured on a prismatic concrete specimen undergoing several cycles of uniaxial compression. The loading was applied (or removed) gradually in predefined small steps (stress-controlled). The surface wave velocity was measured at every load step during both loading and unloading phases. Acoustic Emission (AE) test was conducted simultaneously to monitor the microcracking activities at different levels of loading. It was found that the sonic surface wave velocity is highly stress dependent and the velocity-stress relationship follows a particular trend. The observed trend could be explained by a combination of acoustoelasticity and microcracking theories, each valid over a certain range of applied stresses. Having measured the velocities while unloading, when the material suffers no further damage, the effect of stress and damage could be differentiated. The slope of the velocity-stress curves over the elastic region was calculated for different load cycles. This quantity was normalized to yield a dimensionless nonlinear parameter. This parameter generally increases with the level of induced damage in concrete. KW - Nondestructive testing (NDT) KW - Surface wave velocity KW - Concrete KW - Acoustoelasticity KW - Microcracking PY - 2010 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-215943 UR - http://downloads.hindawi.com/journals/ace/2010/740189.pdf DO - https://doi.org/10.1155/2010/740189 SN - 1687-8094 SN - 1687-8086 VL - 2010 IS - Article ID 740189 SP - 1 EP - 9 PB - Hindawi Publ. Corp. CY - New York, NY, USA AN - OPUS4-21594 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Grohmann, Maria A1 - Müller, Sabine A1 - Niederleithinger, Ernst T1 - Reverse time migration: Introduction of a new imaging technique for ultrasonic measurements in civil engineering N2 - Ultrasonic echo testing is widely used in non-destructive testing in civil engineering to investigate concrete structures, to measure thickness, and to locate and characterise built-in components or inhomogeneities. Currently, synthetic aperture focusing techniques are mostly used for imaging. These algorithms are highly developed but have some limitations. For example, it is not possible to image the lower boundary of built-in components like tendon ducts or vertical reflectors. We adopted reverse time migration for non-destructive testing in civil engineering in order to improve the imaging of complicated structures in concrete. By using the entire wavefield, including waves reflected more than once, there are fewer limitations compared to synthetic aperture focusing technique algorithms. As a drawback, the required computation is significantly higher than that for the techniques currently used. Simulations for polyamide and concrete structures showed the potential for non-destructive testing. The simulations were followed by experiments at a polyamide specimen. Here, having acquired almost noise-free measurement data to test the algorithm, we were able to determine the shape and size of boreholes with sufficient accuracy. After these successful tests, we performed experiments at a reinforced concrete foundation slab. We obtained information from the data by reverse time migration, which was not accessible by traditional imaging. The imaging of the location and structure of the lower boundary of the concrete foundation slab was improved. Furthermore, vertical reflectors inside the slab were imaged clearly, and more flaws were found. It has been shown that reverse time migration is a step forward in ultrasonic testing in civil engineering. T2 - NDT-CE 2015 - International symposium non-destructive testing in civil engineering CY - Berlin, Germany DA - 15.09.2015 KW - Ultrasound KW - Imaging KW - Reverse time migration KW - Reflection seismics KW - Concrete PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-345406 SN - 1435-4934 SP - 1 EP - 10 PB - Technische Universität Berlin / Bundesanstalt für Materialforschung und -prüfung AN - OPUS4-34540 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Niederleithinger, Ernst A1 - Wolf, Julia A1 - Mielentz, Frank A1 - Wiggenhauser, Herbert A1 - Pirskawetz, Stephan T1 - Embedded ultrasonic transducers for active and passive concrete monitoring N2 - Recently developed new transducers for ultrasonic transmission, which can be embedded right into concrete, are now used for non-destructive permanent monitoring of concrete. They can be installed during construction or thereafter. Large volumes of concrete can be monitored for changes of material properties by a limited number of transducers. The transducer design, the main properties as well as installation procedures are presented. It is shown that compressional waves with a central frequency of 62 kHz are mainly generated around the transducer's axis. The transducer can be used as a transmitter or receiver. Application examples demonstrate that the transducers can be used to monitor concrete conditions parameters (stress, temperature, …) as well as damages in an early state or the detection of acoustic events (e.g., crack opening). Besides application in civil engineering our setups can also be used for model studies in geosciences. KW - Ultrasound KW - Transmission KW - Concrete KW - Damages KW - Cracks KW - Stress KW - Monitoring KW - Acoustic emission KW - Transducers KW - Coda wave interferometry PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-345632 DO - https://doi.org/10.3390/s150509756 SN - 1424-8220 VL - 15 IS - 5 SP - 9756 EP - 9772 PB - MDPI CY - Basel AN - OPUS4-34563 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -