TY - JOUR A1 - Strangfeld, Christoph A1 - Klewe, Tim T1 - Comparison of the Calcium Carbide Method and Darr Drying to Quantify the Amount of Chemically Bound Water in Early Age Concrete JF - Materials N2 - Hydration is the exothermic reaction between anhydrous cement and water, which forms the solid cement matrix of concrete. Being able to evaluate the hydration is of high interest for the use of both conventional and more climate-friendly building materials. The experimental monitoring is based on temperature or moisture measurements. The first needs adiabatic conditions, which can only be achieved in laboratory. The latter is often measured comparing the weight of the material sample before and after oven drying, which is time-consuming. This study investigates the moisture content of two cement-based and two calcium sulphate based mixtures for the first 90 days by using the calcium carbide method and oven drying at 40 °C and 105 °C (Darr method). Thereby, the amount of chemically bound water is determined to derive the degree of hydration. The calcium carbide measurements highly coincide with oven drying at 40 °C. The calcium carbide method is therefore evaluated as a suitable alternative to the time-consuming Darr drying. The prompt results are seen as a remarkable advantage and can be obtained easily in laboratory as well as in the field. KW - Concrete KW - Hydration KW - Material moisture KW - Calcium carbide method KW - Bound water KW - Darr method KW - Oven drying KW - Chemisorption KW - Physisorption PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564519 DO - https://doi.org/10.3390/ma15238422 VL - 15 IS - 23 SP - 1 EP - 16 PB - MDPI AN - OPUS4-56451 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Wiehle, Philipp A1 - Munsch, Sarah Mandy T1 - About the dominance of mesopores in physisorption in amorphous materials JF - Molecules N2 - Amorphous, porous materials represent by far the largest proportion of natural and men-made materials. Their pore networks consists of a wide range of pore sizes, including mesoand macropores. Within such a pore network, material moisture plays a crucial role in almost all transport processes. In the hygroscopic range, the pores are partially saturated and liquid water is only located at the pore fringe due to physisorption. Therefore, material parameters such as porosity or median pore diameter are inadequate to predict material moisture and moisture transport. To quantify the spatial distribution of material moisture, Hillerborg’s adsorption Theory is used to predict the water layer thickness for different pore geometries. This is done for all pore sizes, including those in the lower nanometre range. Based on this approach, it is shown that the material moisture is almost completely located in mesopores, although the pore network is highly dominated by macropores. Thus, mesopores are mainly responsible for the moisture storage capacity, while macropores determine the moisture transport capacity, of an amorphous material. Finally, an electrical analogical circuit is used as a model to predict the diffusion coefficient based on the pore-size distribution, including physisorption. KW - Physisorption KW - Mesopores KW - Amorphous materials KW - Macropores KW - Adsorbed water layer thickness KW - Material moisture KW - Moisture distribution PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538525 UR - https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/NILGW2 DO - https://doi.org/10.3390/molecules26237190 VL - 26 IS - 23 SP - 1 EP - 22 PB - MDPI AN - OPUS4-53852 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lu, Xin A1 - Hicke, Konstantin A1 - Breithaupt, Mathias A1 - Strangfeld, Christoph T1 - Distributed Humidity Sensing in Concrete Based on Polymer Optical Fiber JF - Polymers N2 - We present a preliminary investigation on distributed humidity monitoring during the drying process of concrete based on an embedded polymer optical fiber (POF). The water dissipated into the POF changes several properties of the fiber such as refractive index, scattering coefficient and attenuation factor, which eventually alters the Rayleigh backscattered light. The optical time Domain reflectometer (OTDR) technique is performed to acquire the backscattered signal at the wavelengths 650 nm and 500 nm, respectively. Experimental results show that the received signal increases at 650 nm while the fiber attenuation factor clearly increases at 500 nm, as the concrete dries out. In the hygroscopic range, the information retrieved from the signal change at 650 nm agrees well with the measurement result of the electrical humidity sensors also embedded in the concrete sample. KW - Distributed fiber optic sensing KW - Distributed humidity sensing KW - Polymer optical fibers KW - Concrete drying KW - Material moisture KW - Embedded humidity sensors PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-537644 DO - https://doi.org/10.3390/polym13213755 SN - 2073-4360 VL - 13 IS - 21 SP - 3755 PB - MDPI CY - Basel, Switzerland AN - OPUS4-53764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph T1 - Feuchtemessverfahren N2 - Discussion and presentation of different methods for moisture measurements in civil Engineering. T2 - Vorlesung Diagnostik und Ertüchtigung von Bauwerken CY - TU Berlin, Germany DA - 16.05.2018 KW - Material moisture KW - Moisture measurements PY - 2018 AN - OPUS4-44944 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 T2 - Monitoring of the absolute water content in porous 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 T1 - Determination of the diffusion coefficient and the hydraulic conductivity of porous media based on embedded humidity sensors JF - Construction and Building Materials N2 - Reinforced concrete and several other building materials deteriorate during their service life. Almost all deterioration processes are related to moisture. For understanding those processes, knowing the exact amount of the moisture content and the moisture transport characteristics is crucial. In fact, the moisture transport in porous materials is a two-phase flow; consisting of the vapour and the liquid phase. The two corresponding parameters are the diffusion coefficient and the hydraulic conductivity. By means of an inverse approach, these two coefficients are experimentally determined. The moisture transport of eight different screed types during hydration and evaporation is monitored based on embedded humidity sensors. The measured humidity profiles are converted into a pore saturation by adapting the approach of Hillerborg to the measured pore volume distribution. The summation of all pore saturations yields the total moisture content including the ink-bottle effect during desorption. The pore volume distribution was determined by mercury intrusion porosimetry as well as by gas adsorption. The measurement of the humidity and the pore saturation in the entire sample enables to invert the mass balance in order to extract the diffusion coefficient and the hydraulic conductivity. The determined diffusion coefficients of the eight investigated screeds are between m2s-1 and m2s-1. KW - Material moisture KW - Moisture transport KW - Embedded sensors KW - Diffusion coefficient KW - Partially saturated pores PY - 2020 DO - https://doi.org/10.1016/j.conbuildmat.2020.120092 VL - 263 SP - 120092 PB - Elsevier Ltd. AN - OPUS4-51029 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Kruschwitz, Sabine T1 - Determination of readiness for laying based on material moisture, corresponding relative humidity, and water release JF - Materials Testing N2 - The moisture content of the subfloor has to be determined before installation to avoid damages of the floor covering. Only if the readiness for layering is reached, an installation without damages can be expected in all cases. In general, three different approaches exist to measure the residual water content: determination of the moisture content, determination of the water release, or determination of the corresponding relative humidity. All three approaches are tested in laboratory at eight different screed types including two different samples thicknesses in each case. The moisture content and the water release are measured by sample weighing, the corresponding relative humidity is measured by embedded sensors. All three approaches are compared and correlated to each other. The evaluations show only weak correlation and, in several cases, contradicting results. Samples are considered as being ready for layering and not-being ready for layering at the same time, depending on the chosen approach. Due to these contradicting results, a general threshold for the risk of damage cannot be derived based on these measurements. Furthermore, the experiment demonstrates that the measurement of corresponding relative humidity is independent of the considered screed type or screed composition. This makes the humidity measurement to very promising approach for the installation of material moisture monitoring systems in the future. KW - Material moisture KW - Readiness for laying KW - Screed KW - Corresponding relative humidity KW - Partially saturated pores PY - 2020 DO - https://doi.org/10.3139/120.111581 VL - 62 IS - 10 SP - 1033 EP - 1040 PB - Carl Hanser Verlag GmbH & Co. KG CY - München AN - OPUS4-51405 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Munsch, Sarah Mandy A1 - Kruschwitz, Sabine 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 - 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 - TY - CONF A1 - Strangfeld, Christoph A1 - Stolpe, Heiko A1 - Kruschwitz, Sabine ED - Schumann, R. T1 - Correlation between the electric impedance and the water layer thickness in partially saturated screed samples T2 - Berichtsband zur 10. CMM-Tagung - Innovative Feuchtemessung in Forschung und Praxis - Materialeigenschaften und Prozesse N2 - The moisture content of screed samples is monitored by means of embedded sensors. Relative humidity sensors and multi-ring-electrodes are used to measure the spatial moisture distribution during desorption. Based on the humidity data and the pore volume distribution, the moisture and the water layer thickness within the pore space are predicted. Slit shape as well as cylindrical pores are evaluated. Finally, the measured real part of the electrical impedance and the calculated water layer thickness are correlated. Based on the available data, a significant trend change of the impedance is documented at a water layer thickness of approximately 3 nm. This water layer thickness corresponds to a relative humidity of 88.3%. T2 - 10. CMM Tagung CY - Ettlingen, Germany DA - 10.10.2019 KW - Material moisture KW - Screed KW - Embedded sensors KW - Electric impedance KW - Water layer thickness PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494636 VL - 10 SP - 79 EP - 102 PB - CMM, Karlsruher Institut für Technologie CY - Karlsruhe AN - OPUS4-49463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -