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 - 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 - Schmidt, Wolfram A1 - Mota, Berta A1 - Ramirez Caro, Alejandra T1 - Einfluss der gesteinskörnung auf die Rheologie von Beton N2 - Die meisten Einflüsse auf die Rheologie von Beton wirken auf sehr kleinen Skalenebenen. Einflussgrößen im Millimeter oder Zentimeterbereich sind im Wesentlichen auf den Sand und die Gesteinskörnung beschränkt. Letztere machen aber in den meisten Betonen 50 %-70 % des Gesamtvolumens aus, was bei Untersuchungen zur Steuerung der Verarbeitungseigenschaften von Beton häufig vernachlässigt wird. Während Betonzusatzmittel und Zusatzstoffe bei geeigneter Wahl die Rheologie sehr gezielt beeinflussen können, eignen sich Sand und Gesteinskörnung weniger gut zur Steuerung der Rheologie, aber sie tragen zur Rheologie des Gesamtsystems bei. Hierbei können Effekte aus Sand und Gesteinskörnung die Effekte von Zusatzmitteln und Zusatzstoffen überlagern und im ungünstigsten Falle sogar nahezu unwirksam machen. Deshalb sollten Ergebnisse zur Verarbeitbarkeit von Bindemittelsystemen nur mit großer Sorgfalt auf Beton übertragen werden. Es ist wichtig, den Einfluss des Sandes und der Gesteinskörnung besser zu verstehen, um diese so abzustimmen, dass sie Effekte aus Fließmitteln positiv ergänzen anstatt diesen entgegenzuwirken. Durch eine gezielte Abstimmung lassen sich Kosten wirksam sparen. KW - Gesteinskörnung KW - Rheologie KW - Fließgrenze KW - Viskosität KW - Beton PY - 2018 VL - 3 SP - 42 EP - 51 PB - ad-media GmbH CY - Köln AN - OPUS4-47044 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Leinitz, Sarah A1 - Kühne, Hans-Carsten ED - Ludwig, H.-M. T1 - Einfluss der Partikelvolumenfraktion auf die Rheologie und die Effektivität von Polysaccharid-Stabilisierern in Gegenwart von Polycarboxylatether-Fließmitteln N2 - Zur Untersuchung der Wirkungsweise von ST ohne und in Gegenwart von FM wurden Untersuchungen an Zementleimen mit unterschiedlichen Φρ und variierten St-Modifikationen durchgeführt. Folgendes kann zusammengefasst werden: Mit zunehmendem Φρ nimmt der Einfluss aller beobachteten ST auf To und Πpl gegenüber dem wässrigen System ab. Bei hohem Φρ reduzieren alle ST Πpl. Diutan Gum und die hochmodifizierte Stärke können aber ein erhöhtes -r0 bewirken. In Gegenwart von FM werden ST insbesondere bei höheren FM-Dosierungen wirksam mit Bezug auf erhöhtes Πpl. Erhöhtes t0 erzielten nur ST-DG und ST-npg. Setzfließmaßversuche konnten darüber hinaus zeigen, dass Stärken besonders effektiv wirken, wenn der Feststoffgehalt sehr hoch ist, während Diutan Gum eine höhere Wirksamkeit aufweist, wenn höhere Wassergehalte im System sind. Die Wirkungsweise von ST ist sehr stark von p und der Gegenwart von FM abhängig. Die Ergebnisse zeigen. dass für Stärken die Modifikation eine sehr große Rolle spielen kann und dass weitere Untersuchungen zeigen müssen, inwieweit ST auf bestimmte Anwendungen maßgeschneidert werden können. T2 - 19. Ibausil - Internationale Baustofftagung CY - Weimar, Germany DA - 16.09.2015 KW - Fließmittel KW - Stabilisierer KW - Polycarboxylatether KW - Polysaccharide KW - Rheologie PY - 2015 SN - 978-3-00-050225-5 VL - 1 SP - 1-1263 EP - 1-1270 AN - OPUS4-34869 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - The African-European SPIN Network - Linking Experts to Foster Innovation in Cement and Concrete T2 - Workshop Cement and Concrete Technology at the University of the Witwaterand CY - Johannesburg, South Africa DA - 2012-09-07 PY - 2012 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-26728 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Grünewald, S. A1 - Ferrara, L. A1 - Dehn, F. T1 - Design of concrete for high flowability: progress report of fib task group 4.3 N2 - Flowable concretes can differ significantly from traditional vibrated concrete. Concrete types like self-compacting concrete (SCC), ultra high performance concrete (UHPC) and high performance fibre reinforced cementitious composites (HPFRCCs) require novel mix design approaches. This has consequences for the production and the performance in the hardened state. Mix designs for flowable concretes can incorporate a wide variety of innovative admixtures or components: e.g. superplasticisers increase the flowability and allow for significant reduction of the water content, shrinkage compensating admixtures or superabsorbent polymers support sound and damage free curing processes, viscosity modifying admixtures enhance the robustness, and new fibre types allow for sophisticated and tailored structural performance. The new Model Code has limitations regarding the application of flowable concrete, e.g. thresholds for the minimum aggregate size and the maximum strength. Provisions are added to include fibres for structural design. fib Task Group 4.3 aims at facilitating the use of innovative flowable materials for designing concrete structures and considers three aspects of flowable concrete: material properties, production effects and structural boundary conditions and performance. This paper reports about the progress of fib TG 4.3 related to the mix design of flowable concrete and discusses the present state-of-the-art concerning admixtures and robustness. T2 - fib Symposium (Proceedings) - Concrete - Innovation and design CY - Copenhagen, Denmark DA - 18.05.2015 KW - Admixtures KW - Fib model code KW - Fibres KW - Flowable concrete KW - Mix design KW - Robustness PY - 2015 SP - 1 EP - 10 AN - OPUS4-33800 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Wirkungsweise verschiedener Fließmittel N2 - In den vergangenen Jahrzehnten hat sich die Betonbauweise beträchtlich von einer Massenanwendung hin zu einer innovativeren, zukunfts- und leistungsorientierten Werkstofftechnologie weiterentwickelt. Heutzutage besteht Beton nicht mehr länger nur aus Zement, Wasser und Gesteinskörnungen, sondern kann unter Anwendung von Zusatzstoffen und chemischen Zusatzmitteln erheblich verbessert werden. Gleichzeitig beschränken die Betonspezifikationen sich nicht mehr auf den Elastizitätsmodul und Druckfestigkeit, sondern Beton kann ebenfalls zur Erfüllung zahlreicher Anwendungskriterien wie Dauerhaftigkeit, Verarbeitbarkeit, Ästhetik, Brandverhalten und vieler anderer mehr beitragen. Gleichzeitig ist jedoch die Zusammensetzung von Beton wegen der Vielzahl an interagierenden Mischungskomponenten komplizierter geworden. Das Verständnis der Auswirkungen der veränderten Mischungskomponenten ist eine Herausforderung, aber auch der Schlüssel zu einer innovativen Betontechnologie. PY - 2015 SN - 1439-7706 VL - 3 SP - 2 EP - 6 PB - ad-media-Verl. CY - Köln AN - OPUS4-33727 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Mode of action of different superplasticisers 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. At the same time the concrete specifications are no longer limited to Young’s modulus and compressive strength, but concrete may need to be designed for a multiple of application criteria such as durability, workability, optics, fire behaviour, and many more. However at the same time, the composition of concrete has become more complex due to the higher number of mutually interacting mixture constituents. Understanding the effects of changed mixture constituents is challenging but a good understanding is the key to innovative concrete technology. PY - 2015 SN - 1437-9023 IS - 3 SP - 2 EP - 6 PB - ad-media-Verl. CY - Köln AN - OPUS4-33581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Amziane, Sofiane ED - Sonebi, M. ED - Charlet, K. T1 - Mode of operation of polysaccharide stabilising agent in cement based systems and interactions with superplasticisers N2 - Polysaccharides are incorporated into cement based systems in order to modify the rheological properties. Typically cellulose ethers, sphingan gums or starch ethers are applied. Depending upon their chemistry, molecular architecture, and adsorption tendency, polysaccharides interact differently with the entire cementitious system. Some stabilising agents like diutan gum mainly affect the cementitious paste; other stabilising agents like starch tend to interact with the sand fraction and even with the coarse aggregates. Cellulose shows more divers performances. Often stabilising admixtures like polysaccharides are used, when sophisticated rheological properties are adjusted. Therefore, polysaccharides are often used in combination with superplasticisers. This can cause interactions, particularly when the stabilising agent shows a strong tendency to adsorb on particle surfaces. Adsorptive stabilising agents may reduce the amount of adsorbed superplasticisers, thus affecting both viscosity and yield stress, while non-adsorptive stabilising agents mainly affect the plastic viscosity independently of the superplasticiser. Due to the strong influence of superplasticisers on the yield stress, influences of the stabilising agent on the yield stress retreat into the background, so that their major effect is an increase of the viscosity. The paper provides a comprehensive overview of how different polysaccharide superplasticisers affect cementitious flowable systems and points out the challenges of the combined use of polysaccharides and superplasticisers. Based on rheometric experiments and Observations of the hydration process, time dependent effects on the workability as well as of the hydration of cement are presented. T2 - ICBBM 2015 - 1st International conference on bio-based building materials CY - Clermont-Ferrand, France DA - 22.06.2015 KW - Corrosion potential KW - Chloride migration KW - Electrical resistivity KW - Water absorption KW - Freeze-thaw PY - 2015 SN - 978-2-35158-154-4 N1 - Serientitel: Rilem proceedings – Series title: Rilem proceedings IS - PRO 99 SP - 100 EP - 106 AN - OPUS4-33582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Efficiency of high performance concrete types incorporating bio-materials like rice husk ashes, cassava starch, lignosulfonate and sisal fibres T2 - ICBBM - 1st International Conference on Bio-Based Building Materials CY - Clermont-Ferrand, France DA - 2015-06-21 PY - 2015 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-33559 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Supplementary cementitious materials for sustainable and economic binders - European solutions compared to African solutions T2 - PACE-PTS Public Symposium on Cement and Concrete-related Issues for the African Market CY - Dar es Saalam, Tanzania DA - 2015-02-26 PY - 2015 AN - OPUS4-33562 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Mode of operation of polysaccharide stabilising agents in cement based systems and interactions with superplasticisers T2 - ICBBM - 1st International Conference on Bio-Based Materials CY - Clermont-Ferrand, France DA - 2015-06-21 PY - 2015 AN - OPUS4-33560 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Parameters that affect the workability of fresh concrete from nano- to centimetrescale T2 - 2015 SEMINAR SERIES No. 4 School of Civil & Environmental Engineering - University of the Witwatersand CY - Johannesburg, South Africa DA - 2015-05-14 PY - 2015 AN - OPUS4-33563 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Quality Control in Concrete Production - Introduction of control chart systems and the new concept according to EN 206 T2 - Public Seminar at the University of Dar es Salaam CY - Dar es Salaam, Tansania DA - 2014-10-28 PY - 2014 AN - OPUS4-32332 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Steuerung der Mischung N2 - Seit den 1980er Jahren hat sich die Auswahl der zur Modifizierung des Verhaltens und der Leistungsfähigkeit von Beton erhältlichen Zusätzen erheblich verbreitet. Für viele Anwendungen ist die Steuerung der Rheologie PY - 2015 SN - 0014-7699 IS - 5 SP - 50 EP - 55 PB - Vincentz CY - Hannover AN - OPUS4-33577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Frisch- und Festbetonprüfungen - ausgewählte Hinweise aus der Prüfpraxis T2 - Fachtagung "Prüfen und Erhalten von Stahlbeton" CY - Berlin, Deutschland DA - 2014-10-09 PY - 2014 AN - OPUS4-31688 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Sustainable cement extenders and SCMs T2 - Totally Concrete Expo CY - Johannesburg, South Africa DA - 2015-05-12 PY - 2015 AN - OPUS4-33564 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Schmidt, Wolfram A1 - Leinitz, Sarah A1 - Mota, Berta A1 - Crasselt, Claudia ED - Liu, Jiaping ED - Wang, Ziming ED - Holland, Terence ED - Huang, Jing ED - Plank, Johann T1 - Influence of the aqueous phase of cement paste on the rheology in the presence of PCE N2 - The paper presents rheometric results and hydration curves for cementitious systems based on cement mixed with different aqueous phases at solid volume fraction of  = 0.45. The varied aqueous phases were deionized water, limewater, the filter residue of a cement paste mixed at w/c = 2.0, and the filtrate of cement paste at solid volume fraction of 0.45. Each cementitious system provided different amounts and sizes of particles formed in the aqueous phase. The pastes were observed with and without polycarboxylate ether based superplasticizer. It was observed that the presence of particles causes higher PCE saturation dosages to achieve a minimum value, but the minimum value is only affected in the case of large particles. In all cases with and without PCE, the presence of small particles causes increased plastic viscosity. In addition, with decreased number and size of hydrates in the aqueous phase the hydration was retarded, which was specifically pronounced in the presence of PCE KW - Aqueous phase of cement paste KW - Polycarboxylate ether KW - Rheology KW - Yield stress KW - Plastic viscosity KW - Heat of hydration KW - Syngenite KW - Solid volume fraction PY - 2018 SN - 978-1-64195-029-9 SP - SP-329-34, 428 EP - 443 PB - American Concrete Institute CY - Farmington Hill, Michigan AN - OPUS4-47107 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 T1 - Correlation between setting, heat evolution, and deformations of cementitious binder systems depending on type and amount of superplasticizer N2 - Today polycarboxylate ether based superplasticizer (PCE) is commonly used in concrete technology when high flow properties and water reduction are specified. The ionic strength of the polymers’ backbones determines the adsorption behaviour of polymers on clinker and early hydration products. The amount of required polymers for specified flow properties and the performance over the time of casting is thus determined by the molecular structure of the superplasticizer. The time depending consumption of polycarboxylate ether polymers strongly affects the reaction of aluminates and sulphate ions as well as the hydration process in general. Hence, the choice of polymers for particular flow properties greatly affects the very early properties of cementitious materials such as setting, heat evolution and autogenous deformations. In order to better understand how PCEs influence the early properties, mixes from cement, limestone filler, viscosity modifying agent and water were varied with a high and a low charge density superplasticizer in differing amounts. Results are presented from measurements with an automatic Vicat device, an isothermal heat flow calorimeter, and shrinkage cones. Tests were conducted at 5, 20, and 30 °C. It is shown that in presence of PCE the final set correlates well with the inflexion point of the heat flow curve, which emphasises the interrelation between C-S-H formation and setting. No such clear correlation can be found for the initial set, which is attributed to the fact that the initial set is rather a rheological than a structural phenomenon, so that other effects overlap with C-S-H formation. The results demonstrate that for a given polymer concentration low charge density polymers yield earlier setting than high charge polymers. However, this influence is overridden by the influence of the total amount of polymers in a cementitious system. Since PCE is typically added according to rheological specifications, and low charge PCE typically requires higher amounts of polymers than high charge PCE for comparable flow performance, low charge PCE retards setting more than high charge PCE. The paper furthermore points out that there is no significant influence of the polymer type or amount on the early deformations. Since type and amount strongly affect the hydration, it is demonstrated that early setting causes higher strain after the final set. It is hence concluded that higher PCE solid contents reduce the risk of early cracks that occur at time of setting, when a solid structure has already been formed but without resistance against cracks yet. T2 - 13th International congress on the chemistry of cement CY - Madrid, Spain DA - 03.07.2011 KW - Polycarboxylate superplasticizer KW - Setting KW - Heat evolution KW - Autogenous deformation KW - Self-compacting concrete KW - Calorimetry PY - 2011 SN - 978-84-7292-400-0 SP - 384 EP - 391 AN - OPUS4-24097 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Akindahunsi, A. A. A1 - Schmidt, Wolfram A1 - Uzoegbo, H.C. A1 - Iyuke, S.E. ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - The influence of starches on some properties of concrete N2 - Starches and its derivatives are known to exhibit viscosity modifying characteristics. In an ongoing work, the influence of com and cassava starches on some properties of concrete such as compressive strength, heat of hydration and creep are examined. Various percentages (0.0, 0.5, 1.0, 1.5 and 2 %) of starches by weight of cement were added to concrete mixes prepared in the laboratory. Preliminary results of compressive strengths showed that both starches have some positive impact (e.g. there was 5.3 % increase in strength due to a 1 % addition of com starch by weight of cement in comparison to the control while cassava starch of the same percentage gave 4.9 % increase in strength) at certain percentages of starch addition to concrete at 28 days. The creep and hydration results shows the starch additions compares well and in some instance performs better. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 KW - Starches KW - Concrete KW - Compressive strength KW - Heat of hydration KW - Creep PY - 2013 SN - 978-3-9815360-3-4 SP - 637 EP - 645 AN - OPUS4-27756 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Einfluss der Polymerstruktur von Stabilisierern auf die Rheologie von selbstverdichtendem Beton und Mörtel T2 - 20. Kolloquium und Workshop "Rheologische Messungen an mineralischen Baustoffen" CY - Regensburg, Germany DA - 2011-03-01 PY - 2011 AN - OPUS4-23313 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Zum Einfluss von Fließmitteln auf die frühe Zementhydratation T2 - Vortragsreihe der Fakultät für Bauingenierwissenschaften der TU Graz CY - Graz, Austria DA - 2014-10-02 PY - 2014 AN - OPUS4-31687 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Rheology - The Key to Innovation in Concrete T2 - SPIN Meeting and Cement and Concrete Workshop CY - Dar Es Salaam, Tanzania DA - 2012-07-01 PY - 2012 AN - OPUS4-26400 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Cement proficiency testing scheme for Africa T1 - Programm zur Eignungsprüfung von Zement in Afrika N2 - The German BAM Federal Institute for Materials Research and Testing in collaboration with the German Metrology Institute (PTB) are organising an Africa wide Proficiency Testing Scheme for the year 2014 on the testing of cement. The Pan-African Cement Proficiency Testing Scheme PACE-PTS is the second Africa-wide proficiency testing scheme after a first transaction in 2012/2013, where 26 private and public constniction materials testing laboratories from 20 African nations were registered. The testing Programme comprises testing of the major Chemical and physical properties of cement. The testing is conducted according to EN 196. The PACE-PTS is open for private and public laboratories in Africa and the registration is open until March 15, 2014. PY - 2014 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 80 IS - 3 SP - 4 PB - Bauverl. CY - Gütersloh AN - OPUS4-30828 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Einfluss der Partikelvolumenfraktion auf die Rheologie und die Effektivität von Polysaccharid-Stabilisierern in Gegenwart von Polycarboxylatether-Fließmitteln T2 - 19. Internationale Baustofftagung (ibausil) CY - Weimar DA - 2015-09-16 PY - 2015 AN - OPUS4-34499 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Correlation between setting, heat evolution, and deformations of cementitious binder systems depending on type and amount of superplasticizer T2 - XIII ICCC - International Congress on the Chemistry of Cement CY - Madrid, Spain DA - 2011-07-03 PY - 2011 AN - OPUS4-24019 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Process Control of the Rheology of Self-Compacting Concrete Based on Cusum Control Charts T2 - 23. Workshop und Kolloquium "Rheologische Messungen an Baustoffen", Regensburg 2015 CY - Regensburg, Germany DA - 2015-03-11 PY - 2015 AN - OPUS4-33565 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Promising bio-based material solutions for more sustainable concrete N2 - Today, concrete engineers can vary consistencies between very stiff and self-compacting. At the same time engineers can opt for a vast variety of binders. The possibility to use optimised mineral binders and to tailor rheological properties of concrete eventually opened up the path to multiple new technologies, where design criteria are no longer limited to the Young’s modulus and the compressive strength, but often comprise additional added value. It can therefore be concluded that the capability to control the rheology and the interactions particles can be considered as the catalyst for concrete innovations such as polymer modified cementitious composites (PCC) self-compacting concrete (SCC), high-performance concrete (HPC), ultra-high performance concrete (UHPC) or strain hardening cement based composites (SHCC). In the same way rheology modifying additions, SCMs and admixtures will become key parameters in mastering the challenges of the next decades such as: - Additive manufacturing/3D-printing - Overcoming pumping height limitations - Casting at extreme temperatures - Tailored rheology at delivery In many regions in the Southern hemisphere the effective use of SCMs, additions and chemical admixtures for concrete could significantly contribute to solve problems induced by the challenging climatic conditions, but particularly in many countries with challenging climatic conditions, it is difficult to use them, due to lacking local supply and supply infrastructure, and often the awareness of the value of local mineral resources is missing. However, the long distance transportation of mineral resources and chemicals is not very environmentally friendly and the economic consequences are dramatic. However, bio-based constituents and chemicals have been used in construction for ages effectively. Due to the enormous relevance of binders, fillers and rheology modifying admixtures it is worthwhile to recollect that nature provides an enormous variety of products that can be used readily or with low processing. Today, the use of petrol based polycarboxylate ether superplasticizers has become quite common in concrete technology due to their versatility, but their uncomplicated and cost efficient availability is limited in many countries in the world. However, alternatives are available, which can be found locally. In addition many agricultural wastes today are dumped, although they could be converted to reactive ashes easily. Plant extracts have been used to modify the properties of concrete for long time. These plants are typically regionally abundantly available, cheap, and they are environmental friendly. They do not require special caring for seedlings, weeding or manuring to grow since they grow wildly. The talk will present an overview of various options for binders, fillers and rheology modifying admixtures, that can be found in nature, and that may become a real alternative, once their interaction within the complex cementitious system is well understood. T2 - Peak Forum on Sustainable Civil Engineering Materials CY - Shanghai, China DA - 18.05.2017 KW - Cement KW - Concrete KW - Sustainability KW - Bio-based materials KW - Polysaccharides KW - Supplementary cementitious materials PY - 2017 AN - OPUS4-41031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Influence of nano scale effects on the macroscopic rheology 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. Meanwhile admixtures have become common practice in concrete technology, but the understanding of these highly complex polymers in the entire concrete system lags far behind their application. 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. Based on the observations of the nano scale effects, it seems that higher sensitivity against variations in the constituents, the handling, or the boundary condition are the inevitable price for higher performances. However, eventually a very effective method is introduced that helps to maintain stable processes regardless of the root cause for performance changes based on an efficient in-situ process control scheme and superplasticizer and stabilising agents as counter actions. T2 - International Workshop on Nano-Engineered Meta-materials for Civil Infrastructures CY - Jinan, China DA - 20.5.2017 KW - Rheology KW - Meta materials KW - Nano engineering KW - Admixtures KW - Cement KW - Ettringite PY - 2017 AN - OPUS4-41032 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Pirskawetz, Stephan A1 - Kühne, Hans-Carsten ED - Amziane, Sofiane ED - Sonebi, M. ED - Charlet, K. T1 - Efficiency of high performance concrete types incorporating bio-materials like rice husk ashes, cassava starch, lignosulfonate, and sisal fibres N2 - Over the last decades concrete has evolved from a simple mass construction material towards a sophisticated multi-component system. The design parameters for the mixture composition of concrete have significantly increased from strength based towards overall or specific performance based. As a result the variety of concrete has increased yielding a number of special concrete technologies such as Self-Compacting Concrete (SCC), High-Performance Concrete (HPC), Strain Hardening Cement Based Composites (SHCC), and many others. Due to their complex mixture compositions and a multitude of possible interactions between constituents, these concrete types are preferably composed of special components like well-defined powders and sophisticated chemical admixtures. This makes such concrete technology expensive and limits their application to regions with the required material supply chains. The paper puts focus on materials, which are less well studied in conjunction with high performance concrete, but which are available in many developing countries, and in particular sub-Saharan Africa. The paper shows how sec can be designed without polycarboxylate ether superplasticizer and well defined fillers, but with lignosulphonate, cassava starch and rice husk ash. The positive effect of well processed rice husk ashes is demonstrated. Furthermore results are presented of SHCC where typical components like polyvinyl alcohol fibres and fluy ash are replaced by sisal fibres and limestone filler, respectively. The results point out that high performance concrete applications do not have to be limited to a boundary framework with availability of well-defined raw material supply structures and sophisticated admixtures or fibres. Concepts are presented how innovative concrete technologies can be developed based on indigenous materials. T2 - ICBBM 2015 - 1st International conference on bio-based building materials CY - Clermont-Ferrand, France DA - 22.06.2015 KW - Corrosion potential KW - Chloride migration KW - Electrical resistivity KW - Water absorption KW - Freeze-thaw PY - 2015 SN - 978-2-35158-154-4 N1 - Serientitel: Rilem proceedings – Series title: Rilem proceedings N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. IS - PRO 99 SP - 208 EP - 214 AN - OPUS4-33583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Einsparpotenziale bei der Produktion von selbstverdichtendem und hochfestem Beton für Betonfertigteile N2 - Im Betonbau hat sich im Laufe der vergangenen Jahrzehnte ein grundlegender Wandel von einer Massenanwendung hin zu einer innovativen, zukunftsorientierten und leistungsbasierten Baustofftechnologie vollzogen. Heute besteht Beton nicht mehr lediglich aus Zement, Wasser und Gesteinskörnungen, sondern kann durch die Verwendung von Zusatzstoffen und chemischen Zusatzmitteln signifikant verbessert werden. Der im Bereich der Zusatzmittel erzielte Fortschritt ebnete zudem den Weg für die Entwicklung neuer Betontypen wie zum Beispiel selbstverdichtender Beton (SVB) und Hochleistungsbeton (HLB), indem die Verarbeitbarkeit vom Wasser-Zement-Wert (w/z) abgekoppelt wurde. Während der w/z und die Sieblinie der Gesteinskörnungen bei herkömmlichen Betontypen die für die Verarbeitbarkeit relevanten Mischungsparameter darstellten, weisen SVB und HLB komplexere Leistungsparameter auf; in puncto Leistungsfähigkeit fallen hier insbesondere die Mehlkornkomponenten ins Gewicht. Dadurch wird das System komplexer und zugleich anfälliger für Abweichungen bei der Produktion. Erschwert wird die Identifizierung möglicher Einsparpotenziale durch die Schwierigkeit der Vorhersage der Auswirkungen von Veränderungen im Produktionsprozess und bei der Mischung. KW - Selbstverdichtender Beton KW - Hochfester Beton KW - Packungsdichte KW - Fließmittel KW - Rheologie PY - 2016 VL - 2016 IS - 02 SP - 80 EP - 83 PB - Ad-Media CY - Köln AN - OPUS4-36884 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barthel, Maria A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Rogge, A. ED - Meng, B. T1 - Betonpflastersteine mit erweiterten Leistungsmerkmalen T2 - 52. DAfStb-Forschungskolloquium CY - Berlin, Deutschland DA - 2011-11-07 PY - 2011 SN - 978-3-9814281-0-0 N1 - Geburtsname von Barthel, Maria: Meinel, M. - Birth name of Barthel, Maria: Meinel, M. SP - 194 EP - 203 PB - BAM Bundesanstalt für Materialforschung und -prüfung CY - Berlin AN - OPUS4-25182 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Bio-based additives, resins and polymers roles and performances T2 - ICBBM Pre-Conference Seminar: Sustainable Bio-materials from Bio-mass for Use in Construction CY - Clermont-Ferrand, France DA - 2015-06-21 PY - 2015 AN - OPUS4-33561 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Supplementary Cementitious Materials an Admixtures - Part I: Supplementary Cementitious Materials T2 - Totally Concrete East Africa 2014 CY - Dar es Salaam, Tansania DA - 2014-10-28 PY - 2014 AN - OPUS4-32333 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Supplementary Cementitious Materials and Admixtures - Part II: Admixtures for Concrete T2 - Totally Concrete East Africa 2014 CY - Dar es Salaam, Tansania DA - 2014-10-28 PY - 2014 AN - OPUS4-32331 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Meng, Birgit A1 - Kühne, Hans-Carsten A1 - Rosignoli, D. T1 - Development and application of a novel ready-made compound including additions and admixtures for the easy production of SCC - Entwicklung und Anwendung einer neuartigen Werktrockenmischung aus Zusatzstoffen und Zusatzmittel für die einfache Herstellung von SVB N2 - Im Rahmen des europäischen Forschungsprojekts Microcon wurden wirtschaftliche und ökologische Ansätze zur Verwendung von Feinstfüllstoffen – so genannten Microfillern – in Bauprodukten, die auf zementgebundenen Systemen basieren, untersucht. Hauptzielsetzung war die Entwicklung von modifizierten Bindemitteln und Zusätzen für die Transportbeton- und Fertigteilindustrie bis hin zur Marktreife. Eine der Neuentwicklungen war eine leicht handhabbare Werktrockenmischung für selbstverdichtenden Beton (SVB), die alle Schlüsselkomponenten bis auf das Bindemittel und die grobe Gesteinskörnung enthält und eine hohe Robustheit in der Anwendung gewährleistet. KW - Self-Compacting Concrete KW - Robustness KW - Microfiller KW - Rheology KW - On-Site Application III KW - Selbstverdichtender Beton KW - Robustheit KW - Mikrofiller KW - Rheologie KW - Baustellenanwendung PY - 2008 SN - 0373-4331 N1 - Sprachen: Deutsch/Englisch - Languages: German/English IS - 3 SP - 4 EP - 11 PB - Bauverl. BV CY - Gütersloh AN - OPUS4-17125 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit A1 - Brouwers, H.J.H. ED - Aguiar, J. B. ED - Jalali, S. ED - Camoes, A. ED - Ferreira, R.M. T1 - Influence of ambient temperature conditions on the effect of stabilising polymers in cementitious building materials T2 - 13th International Congress on polymers in concrete - ICPIC 2010 CY - Funchal-Madeira, Portugal DA - 2010-02-11 KW - Stabilising agent KW - Polycarboxylate ether KW - Polysaccharides KW - Starch ether KW - Biopolymers KW - Rheology KW - Setting PY - 2010 SN - 978-972-99179-4-3 SP - 241 EP - 248 CY - Funchal-Madeira, Portugal AN - OPUS4-21971 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram A1 - Meng, Birgit T1 - The influence of temperature on self-compacting concrete in presence of superplasticizer and additional admixtures T2 - 5th International RILEM Symposium on Self-Compacting Concrete CY - Ghent, Belgium DA - 2007-09-03 KW - Influence of temperature KW - Self-compacting concrete KW - SCC KW - Superplaticizer KW - Admixtures PY - 2007 SN - 978-2-35158-050-9 VL - 1 SP - 405 EP - 410 CY - Bagneux, France AN - OPUS4-15897 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram T1 - Spezifische Einflüsse der Mischtechnik auf Beton T2 - Mischseminar Betonmarketing Ost "Moderne Betone wirksam mischen" CY - Berlin, Germany DA - 2007-10-30 PY - 2007 AN - OPUS4-16171 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Akindahunsi, A. A. A1 - Uzoegbo, H. Ch. A1 - Schmidt, Wolfram ED - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - Effect of Cassava Starch on Shrinkage Characteristics of Concrete N2 - The use of starch and its derivatives in concrete as an admixture to modify relevant properties of concrete is on the increase in recent times. It is known to modify the rheology, to affect the hydration kinetics of cement, and influence on initial and final setting time of cement. This paper examines the effect of cassava starch on concrete. shrinkage properties of concrete, with and without starch addition, were studied. Various percentages (0, 0.5, 1.0, 1.5 and 2 %) of starches by weight of cement were added to concrete mixes prepared in the laboratory. Shrinkage tests were conducted for duration of up to one year. The result show that concretes with starch additions exhibit lower shrinkage, which is an indication the addition of starch as admixture in concrete improves the ability of the concrete reduce shrinkage problems. T2 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa CY - Dar es Salaam, Tanzania DA - 27.01.2016 KW - Cassava KW - Starch KW - Cement KW - Concrete KW - Shrinkage PY - 2016 SN - 978-3-9817502-3-2 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 187 SP - 196 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36880 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Leinitz, Sarah A1 - Kühne, Hans-Carsten ED - Malhotra, V. M. ED - Gupta, P. R. ED - Holland, T. C. T1 - Effects of particle volume fraction and size on polysaccharide stabilizing agents N2 - Polysaccharides modify the rheological properties of cement based systems. Depending upon their chemistry, molecular architecture, and adsorption tendency, they have different modes of action. Some polysaccharides like diutan gum have strong effect on the fluid phase; others like starch strongly interact with particles. This paper presents effects of diutan gum and starches in presence of polycarboxylates. Rheometric investigations with varied particle volume fractions and increasing coarse aggregate diameters were conducted. The results show that starches have stronger influence on the rheology at high particle volume fractions than diutan gum. At lower particle volume fractions this trend is inverted. Experiments with aggregates sizes up to 16 mm (0.63 in.) indicate that stabilizing agent influences on the effects of aggregates on yield stress were small; however up to 1.0 mm (0.04 in.), a significant effect on the plastic viscosity could be observed, which levelled off at larger diameters. T2 - 11th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete CY - Ottawa, Canada DA - 12.07.2015 KW - Diutan gum KW - Starch KW - Polysaccharides KW - Polycarboxylate ether KW - Volume fraction PY - 2015 SN - 9781942727224 SP - SP-302-03, 39 EP - 52 AN - OPUS4-36861 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Schmidt, Wolfram T1 - Design concepts for the robustness improvement of self-compacting concrete - Effects of admixtures and mixture components on the rheology and early hydration at varying temperatures N2 - In Europe a multi-national research project was initiated entitled “Rational Production and Improved Working Environment through Using Self-Compacting Concrete”, followed by another project entitled “Testing SCC”, which helped spreading the benefits of SCC to a wide range of appliers. This project was also the basis of a widely accepted European guideline on Self compacted concrete published by the European industry association bibm, CEMBUREAU, EFCA, EFNARC, ERMCO, which again builds the basis of the European standards for the testing of SCC (EN 12350, Parts 8 to 12) as well as for the actual modernisation of the European concrete standard EN 206-1. PY - 2014 SN - 978-90-386-3598-9 DO - https://doi.org/10.6100/IR771936 VL - 193 SP - 1 EP - 308 PB - Eindhoven University of Technology CY - Eindhoven, The Netherlands AN - OPUS4-30826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Sonebi, M. A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Rheology modifying admixtures: The key to innovation in concrete technology - a general overview and implications for Africa N2 - Innovative admixture technology has significantly widened up the ränge of possibilities of concrete engineers. For many decades the water to cement ratio (w/c) was the major influencing factor for the performance of concrete. Due to the need to adjust a consistency, which still allowed reasonable workability, the w/c was typically significantly higher than technologically reasonable. Rheology modifying admixtures Support adjusting the concrete consistency largely independent of the w/c. It was only after the invention of the first superplasticizers that modern concrete technology significantly evolved in terms of flowability, strength, and durability, and only due to the steady evolution of the technology modern innovations, such as Self-Compacting Concrete, Ultra-High-Performance Concrete, or Engineered Cementitious Composites were made possible. Today’s superplasticizers are extremely versatile and can be adjusted to individual technologicalspecifications. However, the other side of the coin of versatility is that cementitious Systems incorporating superplasticizers have become more sensitive against environmental influences, such as the environmental temperature, which may cause unwanted effects or demand for supplementary admixture use such as stabilizing admixtures. Hence, concrete mixture composition with admixtures demands for a high level of expertise and offen there is lack of awareness about the mode of Operation of rheology modifying admixtures among concrete technologists. The paper gives a comprehensive overview about rheology modifying admixtures such as superplasticizers or stabilizing agents, and how they can be used depending upon the application in the most favourable way. Based on experiences with the sub-Saharan African concreting boundary conditions, which exhibit many challenges in terms of environmental boundary conditions and construction site logistics, conclusions are finally drawn, how admixtures can be used in the most beneficial way to improve the concrete casting Situation. KW - Rheology KW - Admixtures KW - Concrete KW - Superplasticizers KW - Polycarboxylate ether KW - Viscosity modifying agents PY - 2013 SN - 2224-3224 SN - 2225-0956 VL - 5 SP - 115 EP - 120 PB - International Institute for Conservation of Historic and Artistic Works CY - New York, NY, USA AN - OPUS4-30948 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Rogge, Andreas A1 - Kühne, Hans-Carsten ED - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - Optimising available resources for production of good concrete properties N2 - There is a wide range of research worldwide on supplementary cementitious materials (SCMs) such as fly ash and slag for substituting pure cement. Such materials are suitable to be considered in a cementitious system with ordinary Portland cement (OPC) due to their high pozzolanic properties. In addition, majority of the SCMs are said to significantly improve concrete properties especially in terms of increased strength and durability. Unfortunately, the production of such SCMs is not entirely eco-friendly and also limited to certain parts of the world, hence one has to look at alternative options. The issue of availability of resources is a strong concept that is ever-increasing, and the use of more eco-friendly SCMs in a cementitious system is furthermore attractive. Hence this paper addresses the use of eco-friendly SCMs in concrete such as rice husk ash (RHA). Despite the fact that extensive research has been done on this material, its application in a cementitious system to obtain sufficient concrete properties is still rather limited. In a country like Tanzania, high strength concrete construction is applicable in special construction cases but certainly not a high priority. Majority of construction is still undertaken using normal strength concrete. In a ternary cementitious system consisting of OPC, RHA and other readily available resources such as limestone filler (LSF), normal strength concrete can still be produced having good performance and suitable for regular on-site construction. This paper explains a possible application of obtaining sufficient concrete properties from the available resources. T2 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa CY - Dar es Salaam, Tanzania DA - 27.01.2016 KW - Sub-Saharan Africa KW - Rice husk ash KW - Admixtures KW - Workability KW - Rheology PY - 2016 SN - 978-3-9817502-3-2 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 323 EP - 331 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barthel, Maria A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Rübner, Katrin ED - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - Interactions between waste paper sludge ashes and superplasticizers based on polycarboxylates N2 - In many industrial nations, about two third of the paper demand is covered by recovered paper. A major process step within the treatment of waste paper is the de-inking. It is a floating process yielding paper sludge as a waste product. About 50 % of this residue is used as a fuel. In several cases it is burnt at temperature of about 850 °C and thereafter the accrued ashes are collected in the flue gas filter. During the combustion, kaolinite and calcium oxide generate gehlenite and larnite. Calcite is the main component of waste paper sludge ash (PA).The chemical and mineralogical composition of PA suggests using it as a supplementary cementitious material. In modern construction materials technology, workability aspects gain importance, since for most modern materials the rheology and compaction ability are relevant for the operation at a hardened state. It was observed that PA significantly increases the water demand of powder systems, which can cause serious problems during the casting of mineral binder systems containing PA. It is therefore obvious that binder systems containing PA might demand for the use of superplasticizers. Superplasticizers are polymers with anionic backbone that cause electrostatic and steric repulsion effects upon adsorption on surfaces of particles and hydration phases. In this paper interactions between superplasticizers and waste paper sludge ashes are discussed and analysed. Based on observations of changes in the zeta potential and the dispersion of the particle system, the influence of the charge density of superplasticizers is observed and time dependent effects are demonstrated. T2 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa CY - Dar es Salaam, Tanzania DA - 27.01.2016 KW - Waste paper sludge KW - Rheology KW - Cement KW - Concrete KW - Polycarboxylate ether PY - 2016 SN - 978-3-9817502-3-2 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 181 EP - 186 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36877 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Uzoegbo, H. C. A1 - Makunza, J. K. ED - Malhotra, V. M. ED - Gupta, P. R. ED - Holland, T. C. T1 - Admixture concepts for the Sub-Saharan African environment with indigenous raw materials N2 - The economic use of chemical admixtures depends on supply chains. Therefore, in most regions ins sub-Saharan Africa (SSA), the use of admixtures is not common practice. This amplifies the unfavorable framework for concrete construction such as fragmentary supply chains, high local cement prices, and unfavorable construction site facilities in this region significantly. The use of superplasticizer (SP) and stabilizing agents (STA) can enhance the concrete technology in SSA, since they can disassociate the concrete quality from external boundary influences. After providing a general overview of the peculiarities of the SSA boundary framework, economic concepts are provided, how existing material solutions can be significantly improved by the use of SPs and STAs based on locally available materials such as lignosulphonates and cassava starch. Finally a three step optimization process is described that helps developing flowable concrete based on materials that can be accessed in most locations in SSA. T2 - 11th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete CY - Ottawa, Canada DA - 12.07.2015 KW - Lignosulfonate KW - Polycarboxylate ether KW - Robustness KW - Self-compacting concrete KW - Sub-Saharan Africa PY - 2015 SN - 9781942727224 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - SP-302-37, 491 EP - 505 AN - OPUS4-36860 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Schmidt, Wolfram A1 - Ramirez Caro, Alejandra A1 - Sojref, Regine A1 - Mota Gassó, Berta ED - Greim, M. ED - Kusterle, W. ED - Teubert, O. T1 - Contribution of the coarse aggregates to rheology - effects of flow coefficient, particle size distribution, and volume fraction N2 - In order to observe the effect of the aggregate phases between 2 mm and 16 mm without overlap with rheological effects induced by the cement hy-dration and without interactions with a threshold fine sand particle size that affects both, paste and aggregates, rheological experiments were conducted on a limestone filler based paste mixed with aggregates up to 16 mm. Vari-ous aggregate fractions were blended and mixed with the replacement paste in different volumetric ratios. The dry aggregates’ flow coefficients were determined and compared to yield stress and plastic viscosity values at different aggregate volume fractions. The results indicated that the flow coefficient is not a suitable parameter to predict the performance of the aggregates in the paste. It was shown that the yield stress of pastes is largely determined by the blend of different aggregate fractions, while the plastic viscosity to large extend depends upon the coars-est aggregate fraction. Based on the results, ideal aggregate composition ranges for minimised yield stress are presented. For the plastic viscosity no such grading curves to achieve minimum values could be found, but high viscosity curves are identified. KW - Rheology KW - Flow Coefficient KW - Particle Size Distribution KW - Volume Fraction KW - Cement KW - Concrete KW - Reference Material KW - Limestone Filler PY - 2018 SN - 978-3-7469-1878-5 SP - 96 EP - 108 PB - tredition GmbH CY - Hamburg AN - OPUS4-44434 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Wechselwirkungen zwischen Zusatzmitteln und mineralischen Komponenten in selbstverdichtendem Beton beim Betonieren in unterschiedlichen Temperaturen KW - Self-compacting concrete KW - Admixtures KW - Temperature KW - Rheology KW - Limestone filler KW - Selbstverdichtender Beton KW - Zusatzmittel KW - Temperatur KW - Rheologie KW - Kalksteinmehl PY - 2009 SN - 1439-7706 VL - 2 SP - 32 EP - 38 PB - ad-media-Verl. CY - Köln AN - OPUS4-19412 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mezhov, Alexander A1 - Bright, Asante A1 - Schmidt, Wolfram T1 - Increasing the Incorporation of CO2-Sequestering Materials in Concrete N2 - Concrete is the most widely used construction material accounting for approximately half of all human production throughout history. The production of one ton of cement emits around 600 kg of CO2. With a global cement production estimate of 4.2 billion tons, this results in about 2.5 billion tons of CO2 emissions. This accounts for roughly 7.2% of the total global carbon emissions in 2021. Strategies to decrease carbon emissions in the cement and concrete industry include carbon capture and storage (CCS), reduced binders like ordinary Portland cement (OPC) clinker and optimizing material use through improved processes and structural design. This also means changing architectural vision [6], avoiding concrete where its structural performance is not required and use alternative materials instead, and optimizing the communication among the entire production value chain. T2 - 1st International Conference on Net-Zero Built Environment: Innovations in Materials, Structures, and Management Practices (Net-Zero Future 2024) CY - Oslo, Norway DA - 19.06.2025 KW - Concrete KW - CO2-Sequestering PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638531 DO - https://doi.org/10.1007/978-3-031-69626-8_4 VL - 237 SP - 39 EP - 48 PB - Springer Nature Switzerland AG CY - Schweiz AN - OPUS4-63853 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 - Schmidt, Wolfram ED - Schmidt, Wolfram T1 - Engineering skill requirements to cope with the local and global challenges of the future N2 - In the 21st century, adequate habitat and functioning infrastructure are critical for global societal and economic stability. In addition, growing urbanisation and environmental pollution cause challenges to societies. With increasing velocity, humanity faces that the current way of living is not sustainable. Thus, habitat,infrastructure, urbanisation, environment and sustainability are definitively among the most striking challenges of the 21st century. By consulting, planning, building, maintaining, exploiting and processing of global resources, civil engineers contribute significantly to the existence of these challenges. This is a high responsibility, but due to the heavy involvement, together with adjacent disciplines such as architecture, geosciences, chemistry, physics, environmental sciences and economics, civil engineers also hold the key to mitigate these challenges and provide a brighter global future. Solutions towards greener, more sustainable and economically viable materials do exist, and there is ongoing research on how greener technologies can contribute to better livelihood and economic growth, but their level of implementation is limited, a major reason for which is that these approaches require more fundamental understanding rather than standard application. T2 - ISEE Africa - Innovation, Science, Engineering, Education CY - Nairobi, Kenya DA - 30.01.2019 KW - Civil Engineering KW - Education KW - Sustainability KW - Materials KW - Sciences PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484895 UR - http://isee-africa.com/wp-content/uploads/2019/07/Innovation-Science-Engineering-Education_High-Quality.pdf SN - 978-3-9818564-2-2 SP - 16 EP - 19 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-48489 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barucker-Sturzenbecher, Meike A1 - Schmidt, Wolfram ED - Schmidt, Wolfram T1 - Learning from the future - How children of Mukuru fancy the city of tomorrow N2 - Sustainability means meeting the needs of today without compromising the needs of the next generations. How can we meet the needs of the next generations, if we do not even know what these needs are? If we do not listen to the next generation and learn from them? Do we even meet the needs of today for everyone on earth? T2 - ISEE Africa - Innovation, Science, Engineering, Education CY - Nairobi, Kenya DA - 30.01.2019 KW - Urban planning KW - Concrete KW - Mukuru KW - Africa KW - Sustainability PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484832 UR - http://isee-africa.com/wp-content/uploads/2019/07/Innovation-Science-Engineering-Education_High-Quality.pdf SN - 978-3-9818564-2-2 SP - 194 EP - 197 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-48483 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Anniser, J. A1 - Manful, K. ED - Schmidt, Wolfram T1 - A sustainability point of view on horizontal and vertical urban growth N2 - In many regions of the world the urbanisation process is accelerating dramatically. This puts pressure on urban planners but also politics to develop strategies for sustainable city growth. With the rapidly increasing demand for living space in urban areas, cities typically grow vertically. This is largely driven by real estate markets and sometimes also by the desire for status symbols. Certainly, vertical urban growth makes sense, when horizontal growth destroys important flora and Fauna (e.g. in rain forest regions), but in many cases vertical growth is result of real-estate business and Expansion limitation due to state or country borders. However, economics and borders are made by humans. They follow human-made rules. Gravity does not. Therefore, from a point of view of sustainable materials and resourceuse, the trending vertical growth of cities may come under scrutiny. The following aspects should be considered, when a decision is taken between a new quarter with limited number of storeys or a new skyscraper. T2 - ISEE Africa - Innovation, Science, Engineering, Education CY - Nairobi, Kenya DA - 30.01.2019 KW - Urbanisation KW - Construction KW - Materials KW - Sustainability KW - Carbon emissions PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484848 UR - http://isee-africa.com/wp-content/uploads/2019/07/Innovation-Science-Engineering-Education_High-Quality.pdf SN - 978-3-9818564-2-2 SP - 189 EP - 193 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-48484 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Radebe, N. ED - Schmidt, Wolfram T1 - Biased by analytical equipment N2 - Today, in scientific events often a certain separation between researchers from laboratories with highly sophisticated equipment and those from less privileged laboratories can be observed. It is not an uncommon situation that results presented at conferences are rubbished or ridiculed because the investigator only used low-end analytical methods. The assessment of the study is then biased based on the equipment, regardless of the actual quality of the study. T2 - ISEE Africa - Innovation, Science, Engineering, Education CY - Nairobi, Kenya DA - 30.01.2019 KW - Analytics KW - Africa KW - Bias KW - Science KW - Research PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484877 UR - http://isee-africa.com/wp-content/uploads/2019/07/Innovation-Science-Engineering-Education_High-Quality.pdf SN - 978-3-9818564-2-2 SP - 203 EP - 204 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-48487 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 - Roussel, N. ED - Bessaies-Bey, H. T1 - A simple test method to assess the influence of PCEs on the rheology of flowable cementitious systems N2 - Today’s superplasticizers for self-compacting concrete and high Performance cementitious materials are very versatile. Typically superplasticizers are composed of a polycarboxylic backbone equipped with polyethylene oxide graft chains of variable length and grafting degree. The mode of operation of these admixtures is based on the steric repulsion of the particles upon adsorption. The adsorption is strongly depending upon the charge density of a superplasticizer and the time dependent Adsorption processes control the retention of the flow performance – an important issue particularly for ready-mix and construction site concrete. However, the properties of polycarboxylic superplasticizers typically remain a black box for users. The paper suggests a simple and rapid test method, which can be conducted without sophisticated equipment, to qualitatively distinguish between two types of superplasticizers based on the adsorption mechanism. Interpreting the results in the right way provides a powerful tool to choose the right admixture for individual time dependent flow specifications. T2 - 1st international RILEM conference on rheology and processing of construction materials and 7th RILEM conference on self-compacting concrete CY - Paris, France DA - 02.09.2013 KW - Adsorption KW - Polycarboxylate ether KW - Rheology KW - Slump flow PY - 2013 SN - 978-2-35158-137-7 IS - Chapter 2.1.1 SP - 1 EP - 8 AN - OPUS4-29929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz ED - M. Tyrer, ED - E. Ganjian, ED - West, A. T1 - Influence of rheology modifying admixtures on hydration of cementitious suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed Addition time of PCE SPs on hydration of cement and tricalcium aluminate (C3A) pastes, investigated by isothermal heat flow calorimetry. For cement pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. With delayed PCE addition the cement shows a less retarded setting than with simultaneous addition. The alteration caused by PCE is much more pronounced for C3A and gypsum mixes than for cement. If the SP is added simultaneous, the exothermic peak of C3A is retarded. However, with delayed addition of SP the hydration is shortened, the gypsum depletion is fastened and the exothermic peak occurs less retarded or even accelerated compared to simultaneous addition. It is obvious that for C3A pastes there is less retardation the later the Addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and hydration rates. The rate of reaction in the second stage is lower, discernible in decreased slopes and broader peaks. Besides this, a distinct ramp in the C3A heat flow curves within the first stage of C3A hydration occurs for all pastes with delayed addition of SP, which suggests an accelerated ettringite formation. T2 - 38th Cement and Concrete Science Conference CY - Coventry, UK DA - 10.09.2018 KW - Cement hydration KW - Polycarboxylate ether KW - C3A hydration PY - 2018 SN - 978-1-84600-088-1 SP - 64 EP - 67 CY - Coventry, UK AN - OPUS4-45995 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mota Gassó, Berta A1 - Schmidt, Wolfram A1 - Pauli, Jutta A1 - Sturm, Heinz T1 - Influences of hydration effects on the flow phenomena of concrete with admixtures N2 - Today, chemical admixtures like superplasticisers and stabilising agents are extremely important for modern concrete technology. These agents have meanwhile become common practice in concrete technology, but the understanding within the entire system lags far behind their application. The macroscopic rheology of concrete in the presence of superplasticizers strongly depends upon effects on a much smaller scale such as the hydration of the cement, the adsorption of superplasticizers, and the pore solution chemistry. T2 - 2nd International Conference on the Chemistry of Construction Materials CY - München, Germany DA - 10.10.2016 KW - Rheology KW - Cement KW - Superplasticiser PY - 2016 SN - 978-3-936028-96-6 VL - 50 SP - 276 EP - 279 PB - Gesellschaft Deutscher Chemiker e.V. CY - Frankfurt am Main AN - OPUS4-38849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of rheology modifying admixtures on early hydration of cementitious suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has enormous influence on the early hydration of cement. C3A as the most reactive phase of Portland cement plays a significant role in early hydration reactions and affects the rheological performance. Therefore, this paper presents experimental results about the influence of delayed addition of PCEs on the Hydration of cement and C3A-gypsum pastes investigated by isothermal heat flow calorimetry. Complementary in-situ XRD was carried out on C3A pastes to analyze hydration and phase changes related to the addition of PCE. Cement pastes with a delayed addition of PCE showed less Retardation compared to simultaneous addition. The alteration caused by PCE is much more pronounced for C3A-gypsum mixes. With a delayed addition of SP, the hydration of C3A is less retarded or even accelerated. It is obvious that there is less retardation the later the addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and hydration rates. XRD results showed that more C3A is dissolved in the presence of PCE. Also, the gypsum depletion occurs earlier in the presence of PCE and even faster with delayed addition. Without PCE AFm starts to form just after the gypsum depletion. However, in the presence of PCE AFm already starts to form at the beginning of the hydration. Due to the faster gypsum depletion in the presence of PCE, also the transformation from ettringite into AFm begins earlier, but takes longer as without SP. T2 - 15th International Congress on the Chemistry of Cement CY - Prague, Czech Republic DA - 16.09.2019 KW - Cement KW - C3A KW - Early hydration KW - Polycarboxylate ether (PCE) KW - Delayed addition PY - 2019 SP - 1 EP - 8 AN - OPUS4-49104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shamsuddoha, Md A1 - Hüsken, Götz A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Baeßler, Matthias T1 - Long-term mechanical and shrinkage properties of cementitious grouts for structural repair N2 - Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively. T2 - International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) CY - Rovinj, Croatia DA - 20.03.2019 KW - Grout KW - Long-term shrinkage KW - Micro silica KW - Fly ash KW - Metakaolin PY - 2019 DO - https://doi.org/10.21809/rilemtechlett.2019.82 SN - 2518-0231 VL - 4 SP - 9 EP - 15 PB - RILEM Publications SARL CY - 4 avenue du Recteur Poincaré, 75016 Paris, France AN - OPUS4-48712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schmidt, Wolfram A1 - Tlhatlha, Pheladi A1 - Obeng, Emmanuel A1 - Tsaku, Mawuli Kwaku A1 - Arthur, Daniel Vincent A1 - Dodoo, Alex ED - Schmidt, Wolfram ED - Tlhatlha, Pheladi T1 - A practical handbook for safe, smart and durable construction in Ghana N2 - The handbook provides practical guidelines for safe, efficient, and effective construction in Ghana, focusing on proper cement use, mixing consistencies and techniques, and environmental protection. It emphasizes quality control, safety in handling construction materials, and the importance of using protective equipment to prevent health hazards. KW - Cement strength classifications KW - Cement mixing ratios KW - Quality control PY - 2025 SN - 978-3-00-083134-8 SP - 1 EP - 35 PB - Ghana Standards Authority (GSA) CY - Accra AN - OPUS4-63641 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barthel, Maria A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - Concrete pavers for the mitigation of the urban heat island effect N2 - Nowadays an increasing population escapes from rural to urban regions worldwide. Especially in developing countries the number of inhabitants in urban areas triplicated from the 1950s until today. These changes entail a higher demand for residential buildings and infrastructure. Therefore, the building density and the land sealing rise because of the growing cities. Existing vegetation is replaced by sealed or paved surfaces. Concrete as building material provides a high capacity for heat storage, so that the temperature in densely populated inner cities increases. Hence, the microclimate in cities has become warmer than in the surrounding rural areas. This phenomenon is called Urban Heat Island Effect. In the presented research the aim is to reduce this effect by applying self-cooling concrete pavers at large open areas. These concrete pavers differ from normal pavers by their ability to store water temporarily. Thus these pavements counterbalance the absorption of solar radiation and the subsequent transfer of this heat to the surroundings based on the use of evaporation enthalpy. To bring this concept into practice without losing the mandatory specifications like sufficient compressive strength a multilayer design for the pavers was selected and the concrete mixture compositions were optimized for appropriate water transport properties. For the utilization in climate zones with marginal precipitation events only the concept has to be adapted to the circumstances, for example with a separate water supply. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 KW - Urban heat island effect KW - Earth-moist concrete KW - Concrete multilayers pavers KW - Water storage KW - Self-cooling pavement PY - 2013 SN - 978-3-9815360-3-4 SP - 953 EP - 960 AN - OPUS4-27769 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - SPIN- Spearhead network for innovative,clean and safe cement & concrete technologies N2 - Worldwide, cement and concrete experts are at the cutting-edge to sustainable, green, healthy but nonetheless high-Performance concrete. The current relatively low development of the cement and concrete industry in Africa offers the unique opportunity to start directly on the best achievable and sustainable Level, if only Expertise is sufficiently available. It should not be neglected that concrete is a product with comparably low Transport ranges, which means that an improved concrete market will mainly Support the local economy without exceeding financial Drains to the international market, thus fostering the fight against poverty, which is an urgent Need in most African countries. T2 - Workshop Cement and Concrete for Africa CY - Berlin, Germany DA - 17.08.2011 PY - 2011 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-24728 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, Ines Leana ED - Schmidt, Wolfram ED - Tchetgnia Ngassam, Ines Leana T1 - Cement proficiency testing scheme 2016/2017 - Final report N2 - The cement proficiency testing (PT) scheme was set up by the German Metrology Institute (PTB) and the Federal Institute for Materials Research and Testing (BAM) in 2012. The PT scheme was a spin-off from a European Commission and African, Caribbean and Pacific-Group of States funded project entitled SPIN – Spearhead Network for Innovative, Clean and Safe Cement and Concrete Technologies (www.spin.bam.de). The SPIN project aimed at crosslinking experts in industry and policy making bodies, with the prospect of establishing a sustainable cement and concrete construction capacity in Africa. After a successful first pan-African proficiency testing scheme in 2012/2013, it was decided to establish the scheme permanently and independent of the SPIN project. The main focus of setting up a testing scheme was to enable all cement testing laboratories in Africa to evaluate their competence and efficiency in cement testing and further enhance their capacity to obtain better quality products according to their environment. The acronym developed for the PT scheme is PACE-PTS (Pan-African Cement Proficiency Testing Scheme). The framework for the PT scheme was set up jointly among the organisers and the first participants. The first PT scheme was initiated in Dar Es Salaam in 2012 followed by a final workshop in Berlin in 2013. The second PT scheme began in 2014. A final workshop was organised in Dar es Salaam in 2015. The third and current scheme was started in 2016 and the final workshop is held in Yaoundé. KW - PACE-PTS KW - Round Robin KW - Proficiency testing KW - Cement KW - Quality infrastructure PY - 2017 VL - 3 SP - 1 EP - 74 PB - BAM CY - Berlin AN - OPUS4-43546 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Priebe, Nsesheye Susan ED - Schmidt, Wolfram T1 - Why Africa can spearhead innovative and sustainable cement and concrete technologies globally N2 - The perception of concrete in the society as well as in the politics is rather negative. This becomes obvious in the fact that the phrase “concrete jungle” has become synonym for hapless living with no perspectives. In politics and research funding, it is also not easy to create a broader audience, since concrete is falsely considered as old-fashioned material that is sufficiently understood today and does not need further considerations, particularly compared to allegedly newer materials. However, particularly since the last two decades the technology has completely changed. Binders of today are no more the same binders as used before, and concrete mixture compositions of today diverge quite significantly from compositions in the past. There is little understanding world-wide about that. This causes that potentials the concrete technology bears are wasted. In the broadly found opinion that concrete is old-fashioned and ugly, it is ignored that architectural sins are not inherent to the material, which actually is extremely versatile and CO2-friendly compared to all other construction materials available. It is also ignored that 98% of the outer Earth’s crust are made of the elements cement and concrete are made from, and therefore it will be an illusion to believe that the complementary 2% can create materials to develop regions and infrastructures in less developed areas in the world. For betterment in Africa the infrastructural development should have highest priority, since poor connections between settlements are responsible for enormous Price increases [2], and urban traffic congestion is responsible for an incredible loss of productivity. It is not unrealistic to assume that earners that are dependent on a car get stuck in traffic about 3-4 hours per day in cities like Lagos, Nairobi or Dar es Salaam. However, the traffic congestions do not only affect the car owners negatively but the living of the entire urban population every day. Besides infrastructure, housing should be the other priority, since a large part of the African population does not live in adequate condition. This is a societal problem, since unequal Distribution of wealth is a major driving force for instability in societies. The latter has a global impact, since 8 many phenomena that can be observed all over the world such as political radicalism, xenophobia, terrorism, and migration can often be linked to instable societies. However, the importance of infrastructure has an even wider range. Most African countries go through a change process recently. In order to strengthen very positive perspectives, the focus in politics and research funding is put on issues such as agriculture, energy, and health, which are without doubt extremely important issues. However, it is typically overlooked that all enhancements in these areas can only become effective, when an infrastructure is created to support the implementation of better concepts. Mobility is the key to a prosperous future, and mobility can only be granted by infrastructural construction activities. Hence, compared to many other regions in the world, cement and concrete technologies have a significantly higher relevance in Africa. T2 - 2nd Symposium on Knowledge Exchange for Young Scientists (KEYS) CY - Accra, Ghana DA - 7.6.2016 KW - Cement KW - Concrete KW - Sustainability KW - Carbon dioxide KW - Polysaccharides KW - Cassava KW - Rheology PY - 2016 SN - 978-3-9817853-1-9 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 2 SP - 7 EP - 19 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-40974 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 - Schmidt, Wolfram T1 - Bio-adhesives and bio-chemicals from bio-mass N2 - After a brief introduction into past and modern concrete, the relevance of sustainable concrete technologies is emphasised from a global perspective. In order to minimise the environmental impact of cement and concrete in the world, solutions for alternative binder materials as well as rheology and performance modifying additives are presented based on local bio-based resources. However, the perception of bio-based constituents is typically rather negative in construction materials and its application is often limited to low-end construction. In order to show that this is not inevitable, the lecture ends with a number of case studies for the use of bio-based materials for high performance concrete applications. T2 - Sustainable Adhesives from Bio-Mass (SAB) Symposium CY - Greensboro, North Carolina, USA DA - 26.01.2017 KW - Starch KW - Bio-based materials KW - Superplasticizer KW - Ash KW - Concrete KW - Cement PY - 2017 AN - OPUS4-43544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan T1 - SPIN - Spearhead Network for Innovative, Clean and Safe Cement and Concrete Technologies N2 - Globally, cement and concrete experts are at the cutting-edge to sustainable, green, healthy but nonetheless high-performance concrete. Today concrete is not yet well established in Africa, which offers the unique opportunity to build up a cement and concrete market based on the highest available state of technology. As this industry needs high level expertise, a central issue in implementation of skilled technology is crosslinking research institutions and laboratories. It should not be neglected that concrete is a product with low transport ranges. This means that an improved concrete market mainly supports the local economy without exceeding financial drains to the international market. Thus it fosters the fight against poverty, which is an urgent need in most African countries. The project aims to cross-link experts with industry and policy making bodies, aiming to establish sustainable cement and concrete construction in Africa. KW - High-performance concrete KW - Cement technologies KW - Concrete technologies KW - Sustainable development PY - 2012 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-387428 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 1 EP - 3 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-38742 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Temperature related effects on self-consolidating concrete due to interactions between superplasticizers, supplemental admixtures and additions T2 - 9th ACI International conference on superplasticizers and other chemical admixtures in concrete CY - Seville, Spain DA - 2009-10-12 KW - Polycarboxylate KW - Modified starch KW - Rheology KW - Self-compacting concrete KW - Temperature KW - Setting KW - Shrinkage KW - Heat evolution PY - 2009 SN - 978-0-9731507-8-0 SP - 135 EP - 147 AN - OPUS4-20884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Asante, Bright A1 - Soria-Castro, M. A1 - Schmidt, Wolfram ED - Rogge, Andreas ED - Meng, Birgit T1 - Influence of aquacultural and agricultural bio-admixtures and binder components on yield stress and strength of cementitious systems N2 - Abstract: This study investigates the influence of bio-admixtures and bio-ashes from agricultural and aquaculture residues on the workability and strength of cement mortars. While bio-admixtures at low concentrations can enhance the strength, they create similar or lower yield stress as the reference. Bio ash, particularly at a 10% replacement level, maintained good strength, but higher replacements led to significant reductions in both strength and workability. These findings highlight the potential of sustainable construction materials but emphasize the need to balance performance specifications. T2 - 11. Jahrestagung des DAfStb mit 63. Forschungskolloquium der BAM Green Intelligent Building CY - Berlin, Germany DA - 16.10.2024 KW - Agricultural bio-admixture KW - Aquacultural bio-admixture KW - Binder component PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-612955 SN - 978-3-9818564-7-7 SP - 46 EP - 54 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-61295 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Umeche, E. L. A1 - Schmidt, Wolfram A1 - Uzoegbo, H. Ch. ED - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - A survey and analysis of locally available cements in South Africa N2 - South Africa and recently Nigeria are the only net exporter of cement in Africa, yet cements are imported into the country mainly on the basis of price competitiveness. This poses potential for scatter in the properties of the cements in the South African market as pricing seems to be the only determining factor that affects Portland cements imported. A survey of cements of grade 42.5N in the South African cement market was carried out to identify major players in the industry. The identified cements, which included four locally produced and one imported cement were then analysed for both chemical composition and physical properties in line with the Eurocode EN 196. Tests carried out include loss on ignition, chloride content, sulphate content, specific surface (Blaine), standard consistence, initial setting time, final setting time, soundness and flexural and compressive strength at 2, 7 and 28 days. The testing program was initiated as part of on-going Africa-wide cement testing competency program in partnership with BAM and PTB in Germany. The performance of the identified cements from the different local manufacturers and the imported cement were analysed and are presented in this paper. These results reveal some similarities and differences in the properties. Particularly of interest is the marked difference in the 28 days compressive strength of the cements. This paper shows that there is need for further tests across the cement industry as some of the cements failed to meet certain requirement as set by EN 196. The paper also recommends the use of proficiency testing schemes in the cement industry of the country to ensure the cement laboratories are providing results of high quality and at the same time act as a check to make sure these laboratories are not failing to meet standard requirements. T2 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa CY - Dar es Salaam, Tanzania DA - 27.01.2016 KW - Cement KW - Proficiency testing KW - EN 196 KW - Standards KW - South Africa PY - 2016 SN - 978-3-9817502-3-2 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 91 EP - 98 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36876 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vasilic, Ksenija A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Roussel, N. T1 - Model of SCC flow through reinforced sections: experimental validation N2 - This study focuses on concrete flow in presence of obstacles and develops a mathematical model and a computational approach for SCC flow through reinforced formworks. In order to decrease high computational times needed to simulate castings through reinforced elements, an innovative approach to model the reinforced sections as porous media is proposed here. In the previous work, this numerical model is proved able to simulate the free-surface flow of non-Newtonian fluids through the reinforcement networks. In the present study, the applicability of the model on the concrete flow will finally be proved. The large-scale form-filling experiments with SCC will be conducted and the experiments will be simulated using the proposed numerical model. The numerical model will then be validated through the comparison of the experimental results and the results of the numerical simulations. T2 - 7th RILEM International Conference on Self-Compacting Concrete and 1st RILEM International Conference on Rheology and Processing of Construction Materials CY - Paris, France DA - 02.09.2013 KW - Porous medium KW - Rheology KW - Numerical modelling KW - Reinforcement PY - 2013 SN - 978-2-35158-137-7 SN - 978-2-35158-138-4 SP - 229 EP - 236 PB - RILEM Publishing S.A.R.L CY - Paris, France AN - OPUS4-37442 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 - Einfluss der Lagerungsbedingungen von Zement auf die Verarbeitungs- und Erhärtungseigenschaften von Beton = Effect of the storage conditions of cement on the processing and hardening properties of concrete N2 - In Produktionspausen können in Betonwerken nennenswerte Lagerungsintervalle entstehen. Auf Baustellen und in den Instandsetzungen werden Zement- und Trockenmörtelsäcke teilweise über längere Zeiträume gelagert. Auch im Zusammenhang mit Zementimporten und zunehmend filigran abgestimmten Betonrezepturen die bereits bei kleinen Änderungen der Ausgangsstoffe sensibel reagieren, nimmt die Relevanz der Zementlagerung zu. Aus diesem Grund wurde der Einfluss der Zementlagerung auf die Eigenschaften von Betonen in einer Versuchsreihe an der Bundesanstalt für Materialforschung und -prüfung (BAM) ermittelt. KW - Alterung KW - Zement KW - Sulfationengehalt KW - C3A KW - Rheologie KW - Ageing KW - Cement KW - Sulphate ion content KW - Rheology PY - 2009 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 75 IS - 6 SP - 10 EP - 17 PB - Bauverl. CY - Gütersloh AN - OPUS4-19747 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Performance and interactions of admixtures for SCC exposed to different climatic conditions T2 - CONSEC'07 Tours Concrete under Severe Conditions, CY - Tours, France DA - 2007-06-04 PY - 2007 AN - OPUS4-14874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Beushausen, Hans T1 - Application of a cusum control system for enhanced robustness of the flow properties of self-compacting concrete N2 - Control chart systems are used in quality management systems to keep production processes stable. In concrete production they are often applied for the control of the compressive strength. The most efficient control chart systems are cumulated sums (cusum), which help to observe deviations from a targeted value. Unlike alternative observation chart systems that focus on process data evaluation, cusum observations react very rapidly on systematic process changes in processes. Therefore, the cusum method is particularly suitable if immediate counteractions have to be taken, like in the case of fresh concrete properties of self-compacting concrete (SCC), which can have severe influences on the durability and mechanical strength of concrete. The rheology of SCC can be affected by an enormous variety of influencing factors, from raw material properties to handling or environmental temperature. The present study shows that regardless of the material based influencing parameter for a rheology change, a steady slump flow can be achieved only by adding supplementary superplasticizer in case of loss of flow and adding stabilising agent (ST) in case of increased flow if the respective V-mask indicates a systematic change. A reference SCC was artificially manipulated in order to achieve realistic experimental data for flowability and flowability changes due to changes in the raw material properties. The results point out that productions with applied cusum methods were capable of keeping the target slump flow deviation within approximately 1% only, while productions without applied cusum method deviated up to 14% and more from the target. T2 - fib Symposium 2016. Performance-Based Approaches for Concrete Structures. CY - Cape Town, South Africa DA - 21.11.2016 KW - Concrete KW - Self-compacting concrete KW - cusum KW - control chart KW - quality control KW - robustness PY - 2016 SN - 978-2-88394-121-2 SP - 106-1 EP - 106-10 PB - Fédération internationale du béton ( fib) CY - Lausanne, Switzerland AN - OPUS4-40976 LA - eng 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 composition N2 - Concrete technology was exposed to a rapid development during the last three decades. For the longest time in its history, concrete was considered as a three component System consisting of aggregates, which are bound by the hardened cement paste consisting of hydrated cement. Traditionally, the only way of adjusting the consistency of concrete was using well adjusted aggregates and grading curves and adding excess water to the concrete, accepting that the latter in return reduces strength and durability. During the last three decades, however, concrete has developed further from a three component System towards an (at least) five component system, since the use of mineral additions and Chemical admixtures has become state of the art. Both components are able to enhance the workability, the compactability, and the density of the microstructure with effects on strength, ductility and durability, while cement can be saved in parallel. Due to reasonable use of admixtures and additions, concrete can be designed to match mechanically high performance specifications. Traditionally, cement paste was considered the weakest component in concrete. Flowever, in modern concrete a good paste composition can yield highest performance, passing the role of the mechanical bottleneck towards the aggregates. T2 - Workshop cement and concrete for Africa CY - Berlin, Germany DA - 17.08.2011 KW - Cement KW - Concrete KW - Mixture composition KW - Africa KW - Climatic conditions PY - 2011 SN - 978-3-9814281-4-8 SP - 37 EP - 49 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-24780 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Kühne, Hans-Carsten T1 - Optimising the rheology of concrete for sub-Saharan African boundary conditions / Optimierung der Rheologie von Beton für Rahmenbedingungen in Subsahara-Afrika N2 - Die Zement- und Betontechnologie in Afrika hat keine ähnlich lange Tradition wie viele Länder der nördlichen Hemisphäre. In vielen afrikanischen Ländern ist die Bauindustrie jedoch von Wachstum gekennzeichnet und hier werden Zement und Beton zukünftig zweifelsohne an Bedeutung gewinnen. KW - Africa KW - Cement KW - Concrete KW - Proficiency testing KW - Round robin PY - 2012 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 78 IS - 09 SP - 60 EP - 67 PB - Bauverl. CY - Gütersloh AN - OPUS4-27338 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Uzoegbo, H.C. A1 - Wunderlich, K. A1 - Rongai, G. T1 - A first pan-African proficiency testing scheme / Erstes afrikaweites Programm zur Kompetenzprüfung N2 - Dauerhaftigkeit, Qualität und Sicherheit von Baustoffen gewinnen in afrikanischen Ländern an Bedeutung. In einem Ringversuch testeten 26 Labore des Kontinents ihre Kompetenz bei der Zementprüfung. KW - Viscosity modifying agent KW - Metakaolin KW - Diutan gum KW - Welan gum KW - Rheology PY - 2013 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 79 IS - 09 SP - 42 EP - 53 PB - Bauverl. CY - Gütersloh AN - OPUS4-30044 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Mota, Berta A1 - Ramirez Caro, Alejandra T1 - The action of aggregates on concrete rheology N2 - Most factors acting on concrete rheology work at an extremely small-scale level. Influencing factors in the millimetre or centimetre area are essentially restricted to sand and aggregates. The latter, however, make up 50 to 70% of the total volume of most concretes – a fact often ignored in research on controlling concrete processing properties. Whereas suitably chosen concrete admixtures and additives can influence rheology in a very targeted manner, sand and aggregates are less suitable for controlling rheology but nonetheless contribute to the rheology of the Overall system. The actions of sand and aggregate can impose themselves upon the actions of admixtures and additives and, in unfavourable circumstances, even render them redundant. For this reason, any results concerning the processability of binding agent systems can only be transferred to concrete with great care. It is important to better understand the action of sand and aggregates in order to be able to harmonise them in such a way that they complement the action of superplasticisers positively, instead of working against them. Savings on costs can also be made by this targeted fine-tuning. KW - Rheology KW - Aggregates KW - Viscosity KW - Yield stress KW - Concrete PY - 2018 VL - 3 SP - 42 EP - 49 PB - ad-media GmbH CY - Cologne AN - OPUS4-47045 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Sonebi, M. A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Diouri, A. ED - Khachani, N. ED - Alami Talbi, M. ED - Ait Brahim, L. ED - Bahi, L. T1 - Rheology modifying admixtures: The key to innovation in concrete technology - a general overview and implications for Africa N2 - Innovative admixture technology has significantly widened up the ränge of possibilities of concrete engineers. For many decades the water to cement ratio (w/c) was the major influencing factor for the performance of concrete. Due to the need to adjust a consistency, which still allowed reasonable workability, the w/c was typically significantly higher than technologically reasonable. Rheology modifying admixtures Support adjusting the concrete consistency largely independent of the w/c. It was only after the invention of the first superplasticizers that modern concrete technology significantly evolved in terms of flowability, strength, and durability, and only due to the steady evolution of the technology modern innovations, such as Self-Compacting Concrete, Ultra-High-Performance Concrete, or Engineered Cementitious Composites were made possible. Today’s superplasticizers are extremely versatile and can be adjusted to individual technological specifications. However, the other side of the coin of versatility is that cementitious Systems incorporating superplasticizers have become more sensitive against environmental influences, such as the environmental temperature, which may cause unwanted effects or demand for supplementary admixture use such as stabilizing admixtures. Hence, concrete mixture composition with admixtures demands for a high level of expertise and offen there is lack of awareness about the mode of Operation of rheology modifying admixtures among concrete technologists. The paper gives a comprehensive overview about rheology modifying admixtures such as superplasticizers or stabilizing agents, and how they can be used depending upon the application in the most favourable way. Based on experiences with the sub-Saharan African concreting boundary conditions, which exhibit many challenges in terms of environmental boundary conditions and construction site logistics, conclusions are finally drawn, how admixtures can be used in the most beneficial way to improve the concrete casting Situation. T2 - CMSS 2013 - International congress on materials & structural stability - Building up sustainable materials & constructions CY - Rabat, Morocco DA - 27.11.2013 KW - Rheology KW - Superplasticizers KW - Stabilising agents PY - 2013 SN - 978-9954-32-689-3 SP - 1 EP - 6 AN - OPUS4-30040 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Effects and potentials of plant based chemical admixtures on the performance of cementitious construction materials N2 - While today, engineers can choose from a wide range of rheology modifying admixtures, in some parts of the world, these are difficult to access, due to their complex processing. However, alternatives can be bio-based polymers such as polysaccharides from various sources. These are easily accessible all over the world, do not demand for complicated processing, and typically they are more sustainable than many established materials, which are crude oil-based. The paper presents the effects of acacia gum, cassava starch and the gum of triumfetta pendrata A. Rich on the rheological performance of cementitious systems. It is shown that acacia gum can be as efficient as polycarboxylate based superplasticisers, cassava starch can reduce the yield stress slightly with little effect on the plastic viscosity, and the gum of triumfetta pendrata A. Rich increases the thixotropy of cement pastes with plasticizing polymers significantly. T2 - International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) CY - Rovinj, Croatia DA - 20.03.2019 KW - Polysaccharides KW - Rheology KW - Cement KW - Chemical admixtures KW - Bio-based concrete PY - 2019 AN - OPUS4-47675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Challenges of the growing African cement market – Environmental issues, regulative framework and quality infrastructure requirements N2 - The African cement, concrete and construction business are growing at rapid pace. The cement sales are expected to grow tremendously 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. New 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 CY - Rabat, Morocco DA - 21.11.2017 KW - Quality infrastructure KW - Round Robin KW - Proficiency testing KW - Cement KW - Africa PY - 2017 AN - OPUS4-43543 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pirskawetz, Stephan A1 - Wolf, Julia A1 - Schmidt, Wolfram A1 - Rogge, Andreas T1 - Einsatzmöglichkeiten der Schallemissionsanalyse im Bauwesen N2 - Die Schallemissionsanalyse (SEA) ist ein passives zerstörungsfreies Prüfverfahren. mit dem Rissbildung, Risswachstum und andere Gefügeveränderungen delektiert und lokalisiert werden können. Anhand von zwei Beispielen aus der Forschung der Bundesanstalt für Materialforschung und -prüfung (BAM) wird gezeigt welche Möglichkeiten die SEA beim Bauwerksmonitoring und bei der Untersuchung von Baustoffen bietet. Im ersten Beispiel wird die Ortung von Schallemissionen zur Verfolgung des Risswachstums in Beton eingesetzt. Weiterhin wird mit Zugversuchen an Faserbeton illustriert, dass mit der SEA Versagensmechanismen identifiziert werden können. T2 - 8. Symposium Experimentelle Untersuchungen von Baukonstruktionen CY - Dresden, Germany DA - 24.09.2015 KW - Schallemission KW - SHCC PY - 2015 SN - 1613-6934 N1 - Serientitel: Schriftenreihe Konstruktiver Ingenieurbau Dresden – Series title: Schriftenreihe Konstruktiver Ingenieurbau Dresden VL - 40 SP - 61 EP - 72 PB - Technische Universität Dresden CY - Dresden AN - OPUS4-34581 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vasilic, Ksenija A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram A1 - Roussel, N. T1 - Numerical simulations of scc casting: parameter determination N2 - The paper addresses numerical modelling of fresh self-compacting concrete. In the previous studies, a numerical tool for casting prediction is built based on the assumption that fresh concrete behaves as a yield-stress fluid and treating zones with rebars as porous media. The present contribution discusses the determination of material parameters, which are required as an input for numerical simulations of casting processes. T2 - International RILEM Conference on Materials, Systems and Structures in Civil Engineering 2016, Segment on Fresh Concrete CY - Lyngby, Denmark DA - 22.08.2016 KW - Fresh concrete KW - Simulation KW - CFD KW - Rheology PY - 2016 SN - 978-2-35158-184-1 SP - 163 EP - 172 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-37446 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Peculiarities of African cement and concrete markets: challenges and opportunities N2 - Today's African concrete construction environment differs greatly from that in Europe, Japan or North America. Europe can look back on a concrete tradition of more than 150 years. Standardising documents and guidelines have existed for over 100 years, and formed the foundation of modern Standards adopted and applied in many regions of the world. Technological developments in cement production are also strongly influenced by environmental conditions of the Northern hemisphere. In contrast, with the exception of South Africa, most countries of sub-Saharan Africa started cement production in the 1950s to 1960s, followed by a period of political and economic upheaval. As a result, there have not been serious approaches towards customised Solutions for concrete construction for conditions specific to sub-Saharan Africa; in most countries overseas Standards are applied, as a matter of course. PY - 2013 SN - 1560-2710 VL - 16 IS - 4 SP - 1 PB - Hypenica AN - OPUS4-30419 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Rogge, A. ED - Meng, B. T1 - Zum Einfluss des Mischungsentwurfs und des Fließmittels auf temperaturbedingte Veränderungen der Rheologie von SVB T2 - 52. DAfStb-Forschungskolloquium CY - Berlin, Deutschland DA - 2011-11-07 KW - Fließmittel KW - Polycarboxylatether KW - Selbstverdichtender Beton KW - Temperatureffekte KW - Rheologie PY - 2011 SN - 978-3-9814281-0-0 SP - 40 EP - 49 PB - BAM Bundesanstalt für Materialforschung und -prüfung CY - Berlin AN - OPUS4-25194 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - "Effektivität von Stabilisierern - Einfluss des Feststoffvolumenanteils und Wechselwirkung mit Fließmitteln - "Effectiveness of Stabilising Agents - Influence of the Solid Volume Fraction and Interactions with Superplasticizers" T2 - 23. Konferenz "Rheologische Messungen an Baustoffen" CY - Regensburg, Germany DA - 2014-03-12 PY - 2014 AN - OPUS4-30832 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Govin, Alexandre A1 - Schmidt, Wolfram A1 - Bartholin, M. C. A1 - Grosseau, P. ED - Amziane, Sofiane ED - Sonebi, Mohammed ED - Charlet, Karine T1 - Effect of Guar gum derivatives combined with superplasticizers on properties of Portland cement pastes N2 - Chemical admixtures allow to create a variety of fresh and hardened state properties in cementitious materials. In the case of self-compacting concrete, plasticizers or superplasticizers are introduced with the aim to decrease the yield stress and the viscosity of the materials. However, in order to prevent segregation and bleeding, and to improve the water retention of cement-based system, stabilizing agents or viscosity agents are often introduced in addition. Among these admixtures, polysaccharides are most commonly used. The aim of this study is to provide an understanding of competitive or synergetic effects induced by the combination of hydroxypropyl guar stabilizing agents (HPG) and superplasticizers on cement pastes. Two polycarboxylate superplasticizers (PCE) exhibiting different charge densities and one HPG were studied. It was found that the combination of HPG with PCE superplasticizer strongly affects the rheological behavior of cement pastes. Despite the presence of HPG, the viscosity of the pastes strongly decreased with increasing dosage of PCE until it became close to the viscosity of a cement paste with PCE only. However, the use of HPG in combination with PCE allows maintaining a significant yield stress in the cement paste compared to PCE alone. The increase in the charge density of the PCE seemed to amplify the drop of the viscosity and to reduce the gain on the yield stress induced by HPG. The results also highlight a delay in the setting-time of the cement paste by adding HPG and PCE. The delay induced by HPG is significantly lower than that generated by PCEs. However, the combination of the both kind of admixtures leads to a slightly shorter setting-time compared to the PCE alone. T2 - Second International RILEM Conference on Bio-based Building Materials, 21-23 June 2017 CY - Clermont-Ferrand, France DA - 21.06.2017 KW - Rheology KW - Cement KW - Guar Gum KW - Polysaccharide KW - Superplasticizer PY - 2017 SN - 978-2-35158-192-6 SP - 55 EP - 61 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-43547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Marinescu, M.V.A. A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Uzoegbo, H.C. A1 - Stipanovic Oslakovic, I. A1 - Kumaran, G.S. A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Rogge, Andreas T1 - Recent developments and perspectives regarding the standardisation and quality surveillance of cement in the east, central and south african region N2 - The cement and concrete market in East, Central and Southern Africa is highly fragmented. The concrete industry in this area consists of multiple parties, including producers and suppliers of construction materials, formal and informal contractors, engineers and architects, unions of trades persons and workmen, governmental bodies and formal institutions of research and education. All these institutions mostly do not interact adequately, which makes building with cementitious materials susceptible to damage and failures. Completely opposed to the situation in Europe or North America, cement in Africa is often unaffordable, while manpower is cheap, which results in a questionable economisation of cement. Typically, there is not sufficient awareness of methods to sensibly reducing the cement content in concrete or replace Ordinary Portland Cement by adequate alternative materials. Research activities in this field of technology are often missing completely. Only few countries in the area, such as South Africa, are exempted from these issues. This paper presents the SPIN project, which is a joint project of a consortium of 8 African and 3 European partners within the ACP Science and Technology Programme. The project is funded by the EC and ACP Secretariat is the project body. The main objective of the current project is to strengthen the cement and concrete industry in the East and Central African regions. The project shall generate reasonable solution strategies to implement clean, safe and sustainable cement and concrete technology on the African continent, including general and specific guidelines for sensible application. Furthermore it shall be the kick-off for future projects, research activities and the world-wide expansion of a European-African network. The paper addresses special problems the cement and concrete market in Eastern, Central and Southern African countries has to face. Several options are presented in detail, which shall help overcoming the current situation. Customized solutions for the African market include rational methods for reducing the amount of cement used and the replacement of Ordinary Portland Cement with cheaper alternatives. The use of recycled concrete through a new and economically effective method, as well as the opportunity of using locally available resources is also discussed. T2 - 13th International congress on the chemistry of cement CY - Madrid, Spain DA - 03.07.2011 KW - Africa KW - Clean and safe cement production KW - Scientific network PY - 2011 SN - 978-84-7292-400-0 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 1 EP - 6 AN - OPUS4-24041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - Future civil engineering challenges - Skill requirements, new professional profiles and implementation N2 - Urbanisation, habitat, environment, infrastructure and sustainability are major global challenges of the 21st century. By planning, exploiting of resources, building, and maintaining, civil engineers and relevant adjacent disciplines have been carrying a large responsibility for the existing environmental problems. Civil engineers are responsible for 70% of all material uses in the world, and civil construction has been dominating the growth of the developing world for the next decades, with enormous impact on the global climate as well as the distribution of wealth and quality of living in the world. Today a variety of sustainable construction concepts have been developed and discussed. Recently a UNEP report was published, which provides a comprehensive overview of the challenges and potentials in the future from a scientific and industrial point of view. Sustainable solutions based on abundantly available resources (pozzolana and clay) or on renewable instead of limited industrial by-products (e.g. agricultural waste ashes) and new construction echnologies do exist. By applying, promoting and developing the implementation of the existing knowledge into real life constructions, civil engineers also hold the key for the mitigation of the global challenges. Using best practice sustainable construction solutions is particularly of highest importance in the developing world, since the implementation at an early stage creates the highest leverage for positive effects. T2 - 3rd Symposium on Knowledge Exchange for Young Scientists (KEYS) CY - Johannesburg, South Africa DA - 26.6.2017 KW - Civil Engineering KW - Cement KW - Concrete KW - Global engineering KW - Nano engineered materials KW - Sustainability PY - 2017 SN - 978-3-9818270-7-1 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 3 SP - 9 EP - 14 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-40975 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - Study of the superplasticizer-cement hydration interaction by optical spectroscopy N2 - Nowadays, superplasticizers (SPs) are widely used to increase fluidity and reduce water content in concrete; thus, allowing better workability for final applications. The present study will focus on the hydration effect using comb shape polycarboxylates (PCEs), which are known to allow a very low water/cement ratio (w/c of 0.20) or less.Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules.This encouraged us to assess the potential of these methods, and particularly fluorescence, for the investigation of the interactions that occur at the interface between hydrate surfaces of cement particles and PCE at a very early stage of concrete formation and to differentiate between the impact of PCE’s molecular structures on such interactions. T2 - 2nd International Conference on the Chemistry of Construction Materials CY - Munich, Germany DA - 10.10.2016 KW - Cement KW - Dye KW - Superplasticizers KW - Fluorescence PY - 2016 SN - 978-3-936028-96-6 VL - 50 SP - 260 EP - 263 PB - Gesellschaft Deutscher Chemiker e.V. CY - Frankfurth am Main AN - OPUS4-38881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - A simple test method to assess the influence of pces in the rheology of flowable cementitious systems T2 - 1st International RILEM Conference on Rheology and Processing of Construction Materials and 7th RILEM Conference on Self-Compacting Concrete CY - Paris, France DA - 2013-09-02 PY - 2013 AN - OPUS4-29923 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Rheological Optimisation for Flowable Mixture Compositions Specified for African Boundary Conditions T2 - International Conference on Advances in Cement and Concrete in Africa CY - Johannesburg, South Africa DA - 2013-01-28 PY - 2013 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-27676 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Kusum-Kontrollkarten mit V-Maske in der Prozesssteuerung N2 - Seit Juli 2014 liegt die EN 206:2014 als neue Betonnorm vor. Neben kleineren Änderungen ergibt sich hierdurch als einschneidende Änderung zur Vorgängerversion EN 206-1:2008 ein ergänzendes Konzept zur Konformitätsbewertung der Druckfestigkeit von Beton. An dieser Stelle werden neben dem bekannten Mittelwertkriterium alternativ sogenannte Kontrollkartenverfahren möglich. Für die Konformitätsbewertung stellt in diesem Zusammenhang insbesondere die Kusum-Methode (kumulierte Summen, aus dem Englischen cusum – cumulative sum) ein Novum dar. Weiterführende Informationen zu Kusum-Methode in der Konformitätsbewertung können der Literatur entnommen werden. Eigentlich ist die Kusum-Methode aber nicht für die Konformitätsbewertung entwickelt worden, sondern vielmehr für die Produktionskontrolle. Der Unterschied zwischen Konformitätsbewertung und Produktionskontrolle ergibt sich daraus, dass die Konformitätskontrolle eine Bedeutung für die öffentliche Sicherheit hat und dass eindeutige technische Grenzwerte vorliegen müssen, die nicht unterschritten werden dürfen, während die Produktionssteuerung ein Werkzeug mit frei wählbaren Grenzwerten für Hersteller ist. Der Handlungsbedarf ist für die Produktionskontrolle optional und ergibt sich in der Regel aus Wirtschaftlichkeitsbetrachtungen. PY - 2015 SN - 1439-7706 IS - 4 SP - 38 EP - 44 PB - ad-media-Verl. CY - Köln AN - OPUS4-33580 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -