TY - CONF A1 - Agasty, Amit ED - Nolde, Moana ED - Schwarz, Silke ED - Hüsken, Götz T1 - Impact of shock waves from HE-detonation on reinforced concrete structures – Numerical and field studies N2 - An effective protection of structures against impact from detonation of high explosives (HE) necessitate certain design specifications to be met. In the event of an explosion, accidental or intentional, any damage in its neighborhood (especially, for example, to the structures of strategic importance) should remain as low as possible. The behavior of a structure under the shock loading from an explosion will determine the extent of the damage. The investigation of the relevant phenomena that occur during the event of an explosion is the objective of this study. In accordance with the test parameters, numerical simulations were performed and results were compared with those from field tests. The deformation of the wall under shock impact was simulated by implementing the appropriate interaction of fluid and structure. Moreover, the numerical pressure-time histories in front of the wall were compared with the ones measured in the field by means of piezoelectric pressure gauges, providing a validation for the shock waves’ propagation. T2 - MABS 25 CY - Den Haag, The Netherlands DA - 24.09.2018 KW - Shock-structure-interaction KW - Numerical simulations KW - Field tests KW - Piezoelectric pressure-gauge PY - 2018 SP - P082, 1 EP - 3 AN - OPUS4-46316 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leinitz, Sarah A1 - Schmidt, Wolfram A1 - Mota, Berta A1 - Crasselt, Claudia ED - Ludwig, H.-M. T1 - Einfluss der wässrigen Phase von Zementleim und Polycarboxylatethern auf die Rheologie und die frühe Hydratation von Zement N2 - Die Rheologie von fließfähigen zementären Systemen mit Fließmitteln wird durch eine Vielzahl parallel stattfindender Effekte beeinflusst. Zu diesen Effekten zählen Wechselwirkungen zwischen den Polymeren und Ionen in der Porenlösung, frühe Phasenbildung, zeitabhängige und kompetitive Adsorption zwischen anionischen Polymeren und Sulfationen, Bildung von Phasen in der Porenlösung sowie Morphologieänderungen an Partikeloberflächen. Die frühe Hydratation von Zement, die durch Lösungs- und Fällungsprozesse angetrieben wird, beeinflusst diese Effekte erheblich. Das permanente Ungleichgewicht der Porenlösung führt zu Veränderungen der Partikeloberflächen, welches widerum zur Folge hat, dass rheometrische Messungen dieser Zementleime anfällig für Streuungen sind. Um die Einflüsse aus der Zementhydratation zu minimieren, wurden die rheometrischen Untersuchungen mit Zement in Porenlösung durchgeführt. Die Experimente wurden mit verschiedenen Feststoffvolumenfraktionen durchgeführt und mit den Ergebnissen identischer Systeme mit Wasser anstelle von Porenlösung verglichen. Zusätzlich wurden die gleichen Systeme mit Zugabe von Polycarboxylatethern untersucht. Die Ergebnisse zeigen, dass die Leime mit Wasser niedrigere Werte für Fließgrenze und plastische Viskosität aufweisen, als die Systeme mit Porenlösung. Während die Polymere eine Verminderung der Fließgrenze zur Folge hatte, war die Wirkung von Polymeren auf die plastische Viskosität vernachlässigbar. Zusätzlich wurde die frühe Hydratation unter Verwendung von Wärmeflusskalorimetrie, Rasterelektronenmikroskopie und Nadeleindringtiefe beobachtet. T2 - 20. Internationale Baustofftagung CY - Weimar, Germany DA - 12.09.2018 KW - Rheologie KW - Polycarboxylatether KW - Zementleim KW - Fließmittel PY - 2018 SN - 978-3-00-059950-7 VL - 20 SP - 744 EP - 751 PB - F.A. Finger-Institut für Baustoffkunde CY - Weimar AN - OPUS4-45973 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - Tchetgnia Ngassam, Ines A1 - Breitschaft, G. A1 - Virchow, S. ED - Diouri, A. ED - Boukhari, A. ED - Ait Brahim, L. ED - Bahi, L. ED - Khachani, N. ED - Saadi, M. ED - Aride, J. ED - Nounah, A. T1 - Challenges of the growing African cement market – environmental issues, regulative framework, and quality infrastructure requirements N2 - The African cement, concrete and construction business is growing at rapid pace. The cement sales are expected to grow rapidly until 2050. The number of newly built cement plants increases dramatically and in addition more cements are being imported from outside the continent, e.g. from Turkey, Pakistan, Indonesia, and China, driven by overcapacities in the countries of origin. This causes a high number of potentials and challenges at the same time. Newly built cement plants can operate directly at best technological state of the art and thus incorporate more sustainable technologies as well as produce new and more sustainable products such as cements blended with sustainable supplementary cementitious materials such as calcined clays, and industrial or agricultural by products. At the same time the new variety of binding agent as well as the international imports, which are driven by price considerations, make the cement market prone to quality scatter. This puts pressure on the quality control regulations and institutions to ensure safety of construction, healthy application, and environmental safety for the population. The paper presents possible solutions to build up the rapidly increasing African cement production more sustainably than in the rest of the world as well as the related challenges and obstacles that need to be overcome. Based on experiences with a series of pan-African cement testing laboratory proficiency schemes conclusions are made on technical, regulative and political level. T2 - 2nd International Congress on Materials & Structural Stability (CMSS-2017) CY - Rabat, Morocco DA - 22.11.2017 KW - Quality Infrastructure KW - Africa KW - Proficiency Testing KW - Cement KW - Admixtures PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-444330 DO - https://doi.org/10.1051/matecconf/201814901014 SN - 2261-236X VL - 149 SP - 01014-1 EP - 01014-8 PB - EDP Sciences CY - Les Ulis AN - OPUS4-44433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leinitz, Sarah A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Assessment of rheological effects in the binder on the rheology of mortar and concrete N2 - In the last years flowable concrete has become increasingly important in applications such as, for systems with highly reinforced concrete with a complicated formwork, or sprayed concrete and 3D-printing of concrete. For all these applications it is necessary to have tailored rheological properties. Rheology can be described by values of yield stress and plastic viscosity, which can be determined for example by evaluation of rheometer measurements. But for different materials various rheometers with different geometries and stirrers are being used. To see the effects from paste in concrete, it is necessary to investigate mixes of paste, mortar and concrete, stepwise. But currently there exists no device, which is calibrated for these different systems at once. Due to this fact, conventional tests such as V-funnel efflux-time and flow diameter were determined, as well as rheometer data in different cell sizes and geometries. In this study the assessment of rheological effects in the binder on the rheology of mortar and concrete was investigated by using combination of two rheometers. T2 - Rheologische Messungen an Baustoffen 2018, 27. Workshop und Kolloquium CY - Regensburg, Germany DA - 07.03.2018 KW - Rheology KW - Cement KW - Mortar KW - Upscaling KW - Superplasticizer PY - 2018 SN - 978-3-7469-1878-5 VL - 27 SP - 109 EP - 111 PB - tredition GmbH AN - OPUS4-44444 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta A1 - Mota, Berta A1 - Crasselt, Claudia A1 - Artemeva, Elena A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - A Spectroscopic Study of the Superplasticizer Effect on Early Cement Hydration N2 - Organic/inorganic mixtures were prepared from ordinary Portland cement (OPC), water (w/c 0.22), a fluorescent dye in aqueous solution (stable at alkaline pH; BAM-I), and two different comb shape polycarboxylates (PCEs), i.e., high charge (PCE-HC) and low charge (PCE-LC), respectively. Rheological and calorimetric measurements were performed prior to optical studies in order to select PCE concentrations. Absorption and fluorescence spectroscopy of the system OPC + BAM-I (CBAM-I) revealed maxima of dye BAM-I located at 645 nm and 663 nm, respectively. In presence of PCE-HC and PCE-LC, these mixtures displayed a small red shift in reflectance and a faster decrease in intensity compared to studies with CBAM-I; however, only slight differences were observed between the different PCEs. With time, all systems exhibited a decrease in intensity of BAM-I in absorption/reflectance and emission. This could be caused by dye adsorption and possibly decomposition when in contact with cement particles or hydration products. T2 - The Sixth International Symposium on Nanotechnology in Construction (NICOM6) CY - Hong Kong, China DA - 02.12.2018 KW - Cement KW - Optical Spectroscopy KW - Dye KW - Hydration PY - 2018 SP - 1 EP - 9 AN - OPUS4-49378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Mota, Berta A1 - Artemeva, E. A1 - Pauli, Jutta A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - A spectroscopic study of the superplasticizer effect on early cement hydration N2 - Organic/inorganic mixtures were prepared from ordinary Portland cement (OPC), water (w/c 0.22), a fluorescent dye in aqueous solution (stable at alkaline pH; BAM-I), and two different comb shape polycarboxylates (PCEs), i.e., high charge (PCE-HC) and low charge (PCE-LC), respectively. Rheological and calorimetric measurements were performed prior to optical studies in order to select PCE concentrations. Absorption and fluorescence spectroscopy of the system OPC + BAM-I (CBAM-I) revealed maxima of dye BAM-I located at 645 nm and 663 nm, respectively. In presence of PCE-HC and PCE-LC, these mixtures displayed a small red shift in reflectance and a faster decrease in intensity compared to studies with CBAM-I; however, only slight differences were observed between the different PCEs. With time, all systems exhibited a decrease in intensity of BAM-I in absorption/reflectance and emission. This could be caused by dye adsorption and possibly decomposition when in contact with cement particles or hydration products. T2 - 20. Internationale Baustofftagung CY - Weimar, Germany DA - 12.09.2018 KW - Optical spectroscopie KW - Cement hydration KW - Dyes PY - 2018 SN - 978-3-00-059950-7 VL - 20 SP - 1 EP - 6 PB - F.A. Finger-Institut für Baustoffkunde CY - Weimar AN - OPUS4-46277 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -