TY - JOUR A1 - Schmidt, Daniel A1 - Schwarz, Wolfram T1 - Schichtdickenberechnung aus Mikrosondenmessungen mittels Gaußscher Verteilung PY - 1974 SN - 0028-1042 SN - 1432-1904 VL - 61 IS - 1 SP - 30 EP - 31 PB - Springer CY - Berlin AN - OPUS4-8089 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Daniel A1 - Schwarz, Wolfram T1 - Zum Zusammenhang zwischen der Dicke dünner Metallschichten, der relativen Röntgenintensität und anderen Mikrosonden-Parametern T2 - Gemeinsame Tagung für Elektronenmikroskopie CY - Lüttich, Belgien DA - 1973-09-03 PY - 1974 SN - 0340-3815 VL - 6 SP - 55 EP - 66 PB - Remy CY - Münster, Westf. AN - OPUS4-8090 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwarz, Wolfram A1 - Schmidt, Daniel T1 - A test chart for STEREOSCAN 180 by generating grey-scale signals in staircase form PY - 1978 SN - 0161-0457 SN - 1932-8745 VL - 1 IS - 2 SP - 131 EP - 133 PB - Wiley CY - Hoboken, NJ AN - OPUS4-8950 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Wang, K. ED - Shah, S.P. ED - Khayat, K. T1 - Casting process improvement by optimization of mixture composition and high range water reducing agent modification N2 - Since its invention in the early 1990’s, self-consolidating concrete has never become well established in the ready-mix sectors worldwide. The reason for this can be mainly found in the fact that the sophisticated compositions are sensitive against changing environments. This lack of robustness can be attributed to the interaction between cement hydration reaction and high range water reducing agent (HRWRA). Understanding the relevant mechanisms that control the initial flow performance as well as the flow retention helps optimizing SCC mixtures that perform either steadily in one specific environment or that perform largely similarly at steadily changing environments. This paper depicts how HRWRAs interact with clinker and hydration phases and discusses the important role of the charge density of a polycarboxylic HRWRA in the way the rheology is affected. Based on rheometric results and observations of the Vicat setting times, it is shown that increasing charge densities of the HRWRA and decreasing water to powder ratios (w/p) reduce the flow retention and have lesser retarding effect on the setting. Based on the discussion, optimization procedures for the mixture composition and the HRWRA modification are suggested to achieve optimized performance for varying environmental situations or highest robustness for specific conditions. T2 - SCC 2013 - 5th North American conference on the design and use of self-consolidating concrete CY - Chicago, IL, USA DA - 12.05.2013 KW - Polycarboxylate KW - Cement hydration KW - Adsorption KW - Mixture composition KW - Environmental conditions PY - 2013 SP - 1 EP - 10 AN - OPUS4-28581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Becker, S. A1 - Lu, Z. A1 - Leinitz, Sarah A1 - Schmidt, Wolfram A1 - Stephan, D. A1 - von Klitzing, R. ED - Mechtcherine, V. ED - Khayat, K. ED - Secrieru, E. T1 - Particle Interactions in Silica Systems in Presence of Superplasticizer N2 - The flowability of cement paste is of great importance in today’s construction industry and is influenced by additives such as superplasticizers (SP). One type of SPs are polycarboxylate ether type SPs. These additives electrostatically bind with the negatively charged carboxylic groups at the backbone to the positively charged clinker phases. To model positively charged clinker phases with adsorbed SP, silicon Wafers are pre-coated with cationic polyethylenimine (PEI) and SP is adsorbed onto the coated surface (Si/PEI/SP). Two different polycarboxylate ether type (PCE) SP are compared – one for ready-mix concrete and one for precast concrete. In this preliminary study the interaction forces between Si/PEI/SP surface and a silica microsphere (colloidal probe) are investigated under mild physico-chemical conditions (pH *6, ion concentration <10−5 M) using Colloidal Probe Atomic Force Microscopy (CP-AFM). The interaction force between the model surfaces is attractive for low concentration of SP. The force changes from attractive to repulsive by increasing amount of SP. The force upon approach reveals a biexponential behavior. The exponential decay at large and short surface separations are attributed to electrostatic and steric interactions, respectively. The steric forces of the SP for ready-mix concrete show a steeper onset than the SP for precast concrete. The quantification of these interaction forces will be compared to rheological measurements of similar systems. Furthermore, the parameters will be changed to better approach the conditions in real systems, i.e. higher pH and ionic strength. This helps to understand how the forces on the nanoscale influence the macroscopic rheology. KW - Interfacial forces KW - Silica beads KW - Superplasticizer KW - AFM PY - 2019 SN - 978-3-030-22565-0 DO - https://doi.org/10.1007/978-3-030-22566-7 SN - 2211-0844 VL - 23 SP - 571 EP - 579 PB - Springer ET - 1 AN - OPUS4-49183 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barthel, Maria A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Betontechnologische Ansätze zur Vermeidung innerstädtischer Hitzeinseln N2 - Die Versiegelung von Oberflächen, Bebauung und die Ausweitung städtischer Gebiete führen weltweit besonders in sonnenreichen Regionen zu innerstädtischen Hitzeinseln. Diese Flächen wirken als Wärmespeicher, so dass an Sonnentagen eine Temperaturdifferenz bis zu 10 K zwischen Stadt und umliegendem Land entstehen kann. Verstärkt wird dieser sogenannte Urban Heat Island Effect (UHIE) durch die meist direkte Abführung des anfallenden Regenwassers in die Kanalisation, wodurch eine Kühlung durch stetige Verdunstung unterbunden ist, Mit steigender Urbanisierung wächst auch die Bedeutung dieses Phänomens. Innerstädtische Hitzeinseln ziehen direkte wirtschaftliche und soziale Folgen nach sich, da hohe Temperaturen eine teure Klimatisierung der Städte bedingen. So entsteht ein erhöhter Verbrauch an Ressourcen sowie zusätzliche Abwärme. Das Wohlbefinden und die Gesundheit der Bevölkerung verschlechtern sich bei sehr hohen Temperaturen, was zu sinkender Leistungsfähigkeit und sogar zu einer erhöhten Sterberate führen kann. T2 - 18. Ibausil - Internationale Baustofftagung CY - Weimar, Germany DA - 12.09.2012 PY - 2012 SN - 978-3-00-034075-8 VL - 2 IS - 3.07 SP - 2-0042 EP - 2-0050 AN - OPUS4-26545 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Potentials for savings in the production of self-compacting and high strength concrete for precast concrete elements N2 - Over the course of the last decades, concrete construction has significantly changed from mass application towards sophisticated more innovative, future oriented, and performance based materials technology. Today concrete no longer consists of cement, water, and aggregates, but can be enhanced significantly by using supplementary additions and chemical admixtures. Advancements in admixtures eventually facilitated the development of new concrete types such as self-compacting concrete (SCC) and high performance concrete (HPC) by uncoupling the workability from the water-cement ratio (w/c). While for traditional concrete types the major mixture parameter for the workability and strength were the w/c and the grading of the aggregates, for SCC and HPC the performance parameters are more complicated and the performance depends highly on the powder components. This makes the system more sophisticated and in parallel more prone to scatter during the production. The complexity and difficulty to predict the effects of changes in the process and mixture makes it very difficult to identify the right potentials for savings. T2 - ICCX Central Europe CY - Ossa, Poland DA - 11.02.2016 KW - Rheology KW - Self-compacting concrete KW - High strength concrete KW - Packing density KW - Superplasticizers PY - 2016 SP - 18 EP - 20 AN - OPUS4-36883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Einfluss der Verarbeitungstemperatur auf die Eigenschaften von SVB bei Verwendung von Fließmittel und weiteren Zusatzmitteln N2 - Nachdem vor ca. 20 Jahren in Japan die Entwicklung der selbstverdichtenden Betone begann, dauerte es weitere 10 Jahre, bis diese Entwicklung auch Europa erreichte. Obwohl im Fertigteilsektor bereits deutlich mehr SVB zum Einsatz kommt als im Transportbetonbereich, bleiben die Produktionsmengen hinter dem zurück, was die Potenziale und Chancen dieser Technologie eigentlich erwarten ließen. Eine Ursache für die geringe Marktverbreitung sind die stark schwankenden und teilweise nur schwer beherrschbaren Frischbetoneigenschaften dieser Betone. KW - SVB KW - SCC KW - Zusatzmittel KW - Rheologie KW - Fließmittel Betontechnologie KW - Frischbetoneigenschaften PY - 2007 SN - 0373-4331 IS - 12 SP - 40 EP - 49 PB - Bauverl. BV CY - Gütersloh AN - OPUS4-16444 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Vasilic, Ksenija A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Stark, J. T1 - Experimental and numerical studies on calibration of a rotational rheometer for cementitious materials T2 - 17. Ibausil - Internationale Baustofftagung CY - Weimar, Germany DA - 2009-09-23 PY - 2009 SN - 978-3-00-027265-3 VL - 1 SP - 1-1135 - 1-1140 CY - Weimar AN - OPUS4-20300 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Ramge, Peter A1 - Kühne, Hans-Carsten T1 - Efecto de las condiciones de almacenamiento del cemento en las propiedades de procesamiento y endurecimiento del hormigón / As consequências das condicoes de armazenamento do cimento nas qualidades do processamento e endurecimento do concreto PY - 2009 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Spanisch/Portugiesisch - Languages: Spanish/Portuguese VL - 3 SP - 2 EP - 9 PB - Bauverl. CY - Gütersloh AN - OPUS4-20239 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Challenges of the African Environmental Conditions for Concrete Mixture Compostion T2 - Workshop "Cement and Concrete for Africa", BAM CY - Berlin, Germany DA - 2011-08-17 PY - 2011 AN - OPUS4-24726 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Alexander, Mark A1 - John, Vanderley T1 - Education for sustainable use of cement based materials N2 - Structural design and application have always been linked to the compressive strength of concrete as the main relevant criterion. This was justifiable in the past, where concrete consisted of water, ordinary Portland cement and aggregates, but this concept is no longer relevant for modern and more sustainable cement and concrete. Despite these new developments, existing standards, guidelines and academic curricula have not been much updated and are still used worldwide. There is a need to change this situation by proper education of the users. This overview describes the challenges that arise at a user Level from the higher complexity of modern concrete, and defines needs and requirements for enhanced applicability of sustainable concrete concepts. Furthermore, recommendations are given on how better concrete practice can be communicated to all the involved parties, from civil and design engineers to constructors and site-appliers on the construction site. KW - Cement KW - Concrete KW - Sustainability KW - Environment KW - Carbon footprint KW - Education KW - Climate PY - 2018 UR - https://www.sciencedirect.com/science/article/pii/S0008884616307189?via%3Dihub DO - https://doi.org/10.1016/j.cemconres.2017.08.009 SN - 0008-8846 SN - 1873-3948 VL - 114 SP - 103 EP - 114 PB - Elsevier AN - OPUS4-47673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kühne, Hans-Carsten A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Uzoegbo, H. C. T1 - Building practice and concrete infrastructure development in eastern and southern Africa N2 - The construction sector has traditionally been a source of employment in African regions. However, due to policy changes, cut backs in public investments as well as a fall in the number of employments in the private sector have been observed in many countries. Furthermore a shift from registered companies to informal contractors could be noticed. Many contractors offer services they do not provide permanently or for which the required equipment has to be borrowed. A study that was published in 2000 about the situation in Tanzania pointed out that only ca. 15% of the enterprises that offer concrete works own a concrete mixer. The building practice with concrete varies widely over the African continent. Whereas the level of technology and the infrastructure for cement and concrete in South Africa is elaborate, in East Africa and particularly those that were heavily suffering from civil war during the nineties of the last century, the availability of cement and concrete is poor and these materials are far from being everyday building practice. Most of the population relies on indigenous forms of construction requiring wood obtained from felling of forest trees and ultimately contributing to de-forestation. Informal settlements in South-Africa and Kenya are literal evidence where originally green natural vegetation has been turned into artificial desert-like landscapes. PY - 2011 SN - 1437-9023 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 3 SP - 32 EP - 37 PB - ad-media-Verl. CY - Köln AN - OPUS4-25360 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - EN 206:2014: Cusum method or mean value criterion? / EN 206:2014: Kusum-Verfahren oder Mittelwertkriterium? N2 - Für die Anforderungen an Beton für Gebäude und higenieurbauwerke gilt seil Juli 2014 die EN 206:2.014 anstelle der EN 206-1:2000. In diesem Zusammenhang werden .sogenannte Kontrollkarten für den Konfonnltätsniiehweis zugclassen. Die EN 2.06:2.014 bezeichnet die Verwendung ilcs Mittelwertkritcriuins als Methode B und die Verwen düng von Kontrollkarten als Methode C. Kontrollkarten auf Basis von kumulativen Summen (Kiisum) sind sehr effektive Methoden zur Produktionsstcuerung. Die Anwendung wird In BS 5703-2:2001 geregelt. In England. Südafrika und Australien sind Kusum-Kontrollkartensystcme int Alltag der Betonherstcller etabliert, allerdings dient deren Anwendung nicht dem konkreten Konfbrmitätsnachweis, sondern der Abstimmung einer stabilen und zugleich wirtschafllichcn Produktion. Eine Einführung von Kusum-basierten Kontrollkarten für die Konformitätsbewertung wirft insofern die berechtigte Frage auf, ob das Nachweissystem gleichwertig mit dem bewährten Mittelwertkriterium ist. Im vorliegenden Artikel sollen zunächst kurz die Funktionsweise und die Vorteile von Kusum-Kontrollkarien dargcstclll werden, bevor eine vergleichende Bewertung von Kusum-Mcthode und Mittclwcrtkriterium dun hgelührl wird. KW - EN 206:2014 KW - Cusum method KW - Mean value criterion PY - 2014 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 80 IS - 12 SP - 24 EP - 31 PB - Bauverl. CY - Gütersloh AN - OPUS4-33576 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Paul, S.C. A1 - Pirskawetz, Stephan A1 - Van Zijl, G.P.A.G. A1 - Schmidt, Wolfram T1 - Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC) N2 - This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage. KW - Acoustic emission KW - Crack Detection (B) KW - Microcracking (B) KW - Fibre Reinforcement (E) KW - Tensile Properties (C) PY - 2015 DO - https://doi.org/10.1016/j.cemconres.2014.12.003 SN - 0008-8846 SN - 1873-3948 VL - 69 SP - 19 EP - 24 PB - Pergamon Press CY - New York, NY AN - OPUS4-33579 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -