TY - JOUR A1 - Cunningham, P. R. A1 - Mezhov, Alexander A1 - Schmidt, Wolfram T1 - Revealing Value from Bioderived Polymers: Effects of Locally Sourced Polysaccharides on the Rheology of Limestone Mixtures N2 - Admixtures are important constituents to enhance the performance of concrete. They allow for more efficient use of binders which can mitigate negative environmental impacts from producing cement-based materials. Commonly used rheology modifying agents like polycarboxylate ethers or cellulose ethers are synthetic or semi-synthetic, respectively. This requires additional energy consumption for their production and global supply chains particularly for many developing regions, which will be large consumers of concrete in the future. However, many locally available bio-based polysaccharides could be effectively used instead. These polymers are often overlooked by engineers and scientists due to their limited distribution and inherent complexity, yet they represent an underleveraged source of precursors for admixtures. This study investigates the action mechanisms of some bio-based rheology modifying agents, i.e., acacia gum and miscanthus gum, and provides a comparison to a conventionally modified starch. The results show that the mechanism of action of these polymers is closely related to the composition of the mixture, mixing regime, and the composition of the aqueous phase. Depending on the agent, either plasticizing or stabilizing effects on rheology can be revealed. T2 - ICBBM: International Conference on Bio-Based Building Materials CY - Vienna, Austria DA - 21.06.2023 KW - Polysaccharides KW - Superplasticizers KW - Hydration KW - Cement PY - 2023 U6 - https://doi.org/10.1007/978-3-031-33465-8_60 SN - 2211-0852 VL - 45 SP - 782 EP - 792 PB - Springer Nature Switzerland AG CY - Switzerland AN - OPUS4-58726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kruschwitz, Sabine A1 - Munsch, Sarah A1 - Telong, Melissa A1 - Schmidt, Wolfram A1 - Bintz, Thilo A1 - Fladt, Matthias A1 - Stelzner, Ludwig T1 - The NMR core analyzing TOMograph: A multi-functional tool for non-destructive testing of building materials N2 - NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material. Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure. Moreover it enables the determination of moisture transport properties and the (re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing. However, as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale (< 10 mL) samples. This paper describes the capabilities of an NMR tomograph, which has been specifically optimized for the investigation of larger, heterogeneous building material samples (diameters of up to 72 mm, length of up to 700 mm) with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times (50 - 80 m s). KW - Fire spalling KW - Moisture transport KW - Concrete KW - Cement hydration KW - Sensitivity KW - Supplementary cementitous materials KW - Frost salt attack PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-573755 SP - 1 EP - 13 PB - Elsevier B.V. AN - OPUS4-57375 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mezhov, Alexander A1 - Zhang, K. A1 - Schmidt, Wolfram T1 - Interactions of Biobased Rheology Modifying Agents with Superplasticizer in Cement Paste N2 - Organic admixtures are an indispensable component of modern concrete. Thus, their purposeful application is not only technically and economically viable but in addition an inevitable tool to make concrete more environmentally friendly. In this context, the use of polysaccharides has increasingly gained interest in the built environment as sustainable resource for performance enhancement. However, due to its origin, biopolymers possess a vast variety of molecular structures which can result in incompatibilities with other polymers present in concrete, such as superplasticizers. The present study highlights effects of the joint application of different types of starches and polycarboxylates with respect to their influence on cement hydration and structural build-up of cement pastes. KW - Polysaccharides KW - Superplasticizers KW - Hydration KW - Cement PY - 2022 U6 - https://doi.org/10.4028/www.scientific.net/CTA.1.563 SN - 2674-1237 SP - 563 EP - 568 PB - Trans Tech Publications Ltd, Switzerland CY - Basel, Switzerland. AN - OPUS4-58325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bessaies-Bey, H. A1 - Khayat, K. H. A1 - Palacios, M. A1 - Schmidt, Wolfram A1 - Roussel, N. T1 - Viscosity modifying agents: Key components of advanced cement-based materials with adapted rheology N2 - Viscosity modifying agents (VMAs) are essential ingredients for the production of flowable cement-based materials. This paper presents an overview of commonly used VMAs and attempts to shed some light on the underlying physics at the origin of their mechanisms of action. The main molecular parameters of VMA controlling the rheological properties of the cement pore solution are highlighted. As the mechanisms of action of VMAs in cement-based materials are closely related to their affinity with the surface of cement particles, the adsorption of the main VMA types is discussed. The effect of VMAs on flow properties and stability of cement-based materials is presented for VMAs added without any superplasticizer, and then in systems incorporating both VMAs and superplasticizers. Finally, the effect of VMAs in enhancing concrete properties to secure adequate performance of different construction applications, and perspectives for future developments of novel cement-based materials made with VMAs are showcased. KW - Viscosity modifying agents KW - Cement KW - Stability KW - Rheology KW - Working mechanism KW - Compatibility PY - 2022 U6 - https://doi.org/10.1016/j.cemconres.2021.106646 VL - 152 SP - 1 EP - 20 PB - Elsevier AN - OPUS4-58396 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 U6 - 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 - 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 - 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 - JOUR A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, Ines Leana A1 - Olonade, K. A. A1 - Mbugua, R. A1 - Kühne, Hans-Carsten T1 - Plant based chemical admixtures – potentials and effects on the performance of cementitious 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 triumfet ta pendrata A. Rich increases the thixotropy of cement pastes with plasticizing polymers significantly. KW - Polysaccharides KW - Rheology KW - Cement KW - Chemical admixtures KW - Bio-based concrete PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-476748 VL - 3 SP - 124 EP - 128 PB - RILEM S.A.R.L. CY - Paris AN - OPUS4-47674 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 - JOUR A1 - Vasilic, Ksenija A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Roussel, N. T1 - Numerical modelling of SCC flow through reinforced sections T1 - Numerische Simulation des Fließverhaltens von SVB durch bewehrte Querschnitte N2 - The study introduces the porous medium model for the simulation of concrete flow through highly-reinforced sections. It shows that numerical simulations can predict concrete behavior during casting and help to avoid expensive mistakes. N2 - Bei der hier dargestellten Untersuchung wird das Modell des porösen Mediums auf die Simulation des Fließverhaltens von Beton durch Querschnitte mit hohem Bewehrungsgrad angewandt. Dabei zeigt sich, dass mit Hilfe numerischer Simulationen das Verhalten des Betons während der Betonage prognostiziert und kostspielige Fehler vermieden werden können. PY - 2015 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 81 IS - 03 SP - 50 EP - 55 PB - Bauverl. CY - Gütersloh AN - OPUS4-33151 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -