TY - RPRT A1 - Ebell, Gino A1 - Burkert, Andreas A1 - Gehlen, C. A1 - Keßler, S. T1 - Validierung zerstörungsfreier Messmethoden zur zuverlässigen Erfassung von Bewehrungskorrosion (Schlussbericht) N2 - Determining a pore structure’s mechanical and chemical data on lime rendering exposed outdoors and including masonry in the laboratory, with regard to their behaviour on moisture transport and weathering was the objective. In search of clues for a dose-response relation - i.e. upon a connection between the emission rate of SO2 and NOx on one hand and the degree of damage to mainly plaster having a lime component on the other - it has been of interest to what extent their structural characteristics including pore space are modified and so consequently also physico-technical properties and chemical composition. For determining corresponding criteria, a widely diversified spectrum of test methods such as to obtain data concerning porosity and moisture transport, mechanical behaviour, and chemistry as well is available. A description of the manufacture of plate-shaped rendering specimens with lime putty, industrially hydrated lime and dolomitic hydrate (the last two also having a cement admixture) and also hydraulic lime as binding agents is included. First deposition velocity and absorption rate for SO2 were determined in laboratory tests on these materials in dry and moist states. After their exposure on outdoor racks at six locations in the Berlin region with differing SO2 atmospheric contents over at least 5 years, the samples of course show timedependent modifications of chemical and physical qualities which are especially reflected in the form of profiles of structure, strength and concentration, e.g. for sulphate. Local climatic differences, however, partly exert a greater influence on material than emissions. Similar investigations were performed on samples of comparable composition exposed 4 and 17 years. But the real surprise is furnished by the renderings’ behaviour depending upon orientation and upon height at a building. Since weathering behaviour and moisture Transport (absorption, storage, release) are directly interdependent, further criteria are necessary for a critical assessment of a plasters’ pore structure. Starting from sands, plasters were characterized. The structural parameters were lastly influenced by the respective contents of sand, binder and mixing water. These results and those gained from bricks naturally find their expression in masonry sections manufactured there from, and above all in their capillary and evaporative behaviours, and also when applying different test liquids. Summary and cited literature is given at the end of this report. KW - Potentialfeldmessung KW - Potential mapping KW - Korrosion KW - Stahlbeton KW - Betonstahl KW - Merkblatt B 3 PY - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-336229 SP - 1 EP - 92 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) / Technische Universität München AN - OPUS4-33622 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Haist, M. A1 - Link, J. A1 - Nicia, D. A1 - Leinitz, Sarah A1 - Baumert, C. A1 - von Bronk, T. A1 - Cotardo, D. A1 - Eslami Pirharati, M. A1 - Fataei, S. A1 - Garrecht, H. A1 - Gehlen, C. A1 - Hauschildt, I. A1 - Ivanova, I. A1 - Jesinghausen, S. A1 - Klein, C. A1 - Krauss, H.-W. A1 - Lohaus, L. A1 - Lowke, D. A1 - Mazanec, O. A1 - Pawelczyk, S. A1 - Pott, U. A1 - Radebe, N. W. A1 - Riedmiller, J. J. A1 - Schmid, H.-J. A1 - Schmidt, Wolfram A1 - Secrieru, E. A1 - Stephan, D. A1 - Thiedeitz, M. A1 - Wilhelm, M. A1 - Mechtcherine, V. T1 - Interlaboratory study on rheological properties of cement pastes and reference substances: comparability of measurements performed with different rheometers and measurement geometries N2 - This paper presents the results of an interlaboratory study of the rheological properties of cement paste and ultrasound gel as reference substance. The goal was to quantify the comparability and reproducibility of measurements of the Bingham parameters yield stress and plastic viscosity when measured on one specific paste composition and one particular ultrasound gel in different laboratories using different rheometers and measurement geometries. The procedures for both in preparing the cement paste and carrying out the rheological measurements on cement paste and ultrasound gel were carefully defined for all of the study’s participants. Different conversion schemes for comparing the results obtained with the different measurement setups are presented here and critically discussed. The procedure proposed in this paper ensured a reasonable comparability of the results with a coefficient of variation for the yield stress of 27% and for the plastic viscosity of 24%, despite the individual measurement series’ having been performed in different labs with different rheometers and measurement geometries. KW - Rheometry KW - Rheology KW - Interlaboratory test KW - Test setup KW - Testing procedure KW - Cement paste KW - Ultrasound gel PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-511220 SN - 1871-6873 VL - 53 IS - 4 SP - 92 PB - Rilem AN - OPUS4-51122 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Diewald, F. A1 - Epple, Niklas A1 - Kraenkel, T. A1 - Gehlen, C. A1 - Niederleithinger, Ernst T1 - Impact of External Mechanical Loads on Coda Waves in Concrete N2 - During their life span, concrete structures interact with many kinds of external mechanical loads. Most of these loads are considered in advance and result in reversible deformations. Nevertheless, some of the loads cause irreversible, sometimes unnoticed changes below the macroscopic scale depending on the type and dimension of the impact. As the functionality of concrete structures is often relevant to safety and society, their condition must be known and, therefore, assessed on a regular basis. Out of the spectrum of non-destructive monitoring methods, Coda Wave Interferometry using embedded ultrasonic sensors is one particularly sensitive technique to evaluate changes to heterogeneous media. However, there are various influences on Coda waves in concrete, and the interpretation of their superimposed effect is ambiguous. In this study, we quantify the relations of uniaxial compression and uniaxial tension on Coda waves propagating in normal concrete. We found that both the signal correlation of ultrasonic signals as well as their velocity variation directly reflect the stress change in concrete structures in a laboratory environment. For the linear elastic range up to 30% of the strength, we calculated a velocity variation of −0.97‰/MPa for compression and 0.33%/MPa for tension using linear regression. In addition, these parameters revealed even weak irreversible changes after removal of the load. Furthermore, we show the time-dependent effects of shrinkage and creep on Coda waves by providing the development of the signal parameters over time during half a year together with creep recovery. Our observations showed that time-dependent material changes must be taken into account for any comparison of ultrasonic signals that are far apart in time. The study’s results demonstrate how Coda Wave Interferometry is capable of monitoring stress changes and detecting even small-size microstructural changes. By indicating the stated relations and their separation from further impacts, e.g., temperature and moisture, we anticipate our study to contribute to the qualification of Coda Wave Interferometry for its application as an early-warning system for concrete structures. KW - Ultrasound KW - Coda Wave Interferometry (CWI) KW - Mechanical Load KW - Microstructure KW - Concrete PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-556878 SN - 1996-1944 VL - 15 IS - 16 SP - 1 EP - 15 PB - MDPI AN - OPUS4-55687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -