TY - CONF A1 - Schmidt, Wolfram A1 - Uzoegbo, H.C. A1 - Bella, N. A1 - Rongai, G. A1 - Kühne, Hans-Carsten A1 - Diergardt, T. ED - Diouri, A. ED - Khachani, N. ED - Alami Talbi, M. ED - Ait Brahim, L. ED - Bahi, L. T1 - Cement testing in Africa - Conclusions from the first africa-wide proficiency testing scheme N2 - African cement inffastructure is quite complex. Apart from Northern Africa and South Africa in particular, cement plants are scarce resulting in highly unstable cement pricing. Clinker and cement are imported from overseas, e.g. from Portugal, Turkey, Pakistan, Indonesia, and China. Imports are typically determined by the lowest price, and as a result the countries of origin of products vaiy regularly yielding large scatter of properties. Quality control and a good quality infrastructure are thus of utmost importance for the safety of the popuiace, an issue, which is actually often neglected. With funding of the German Metrology Institute (PTB) and Support of the SPIN project, a proficiency testing scheme for cement testing according to EN 196 was set up for African laboratories. Proficiency testing schemes, also called round robins. are interlaboratory performance comparisons allowing participants to evaluate themselves against pre-established criteria. Thev are a powerful tool to help laboratories improve their performance as well as demonstrate their competences to accreditation bodies or Customers. 26 laboratories from 20 nations, 18 of which from Africa, participated. The BAM Federal Institute for Materials Research and Testing acted as coordinator and provider of the scheme. The aim of the round robin was to interpret the submitted data further beyond the pure statistic analyses. The data provided a positive picture of the performance of the participants in general, but it also exhibited a number of technical fields that need improvement. The paper provides the general results of the scheme and analyses identified strengths and weak points based on the submitted and non submitted data as well as on discrepancies from the EN 196 procedures during measurements. The application of EN Standards for material testing is critically discussed and since quality infrastructure is also always an issue between industrial and political stakeholders, suggestions for the mitigation of the identified shared problems are given. T2 - CMSS 2013 - International congress on materials & structural stability - Building up sustainable materials & constructions CY - Rabat, Morocco DA - 27.11.2013 KW - Viscosity modifying agent KW - Metakaolin KW - Diutan gum KW - Welan gum KW - Rheology PY - 2013 SN - 978-9954-32-689-3 SP - 1 EP - 5 AN - OPUS4-30042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Uzoegbo, H.C. A1 - Bella, N. A1 - Rongai, G. A1 - Kühne, Hans-Carsten A1 - Diergardt, T. T1 - Cement testing in Africa - Conclusions from the first africa-wide proficiency testing scheme N2 - African cement infrastructure is quite complex. Apart from Northern Africa and South Africa in particular, cement plants are scarce resulting in highly unstable cement pricing. Clinker and cement are imported from overseas, e.g. from Portugal, Turkey, Pakistan, Indonesia, and China. Imports are typically determined by the lowest price, and as a result the countries of origin of products vary regularly yielding large scatter of properties. Quality control and a good quality infrastructure are thus of utmost importance for the safety of the populace, an issue, which is actually often neglected. With funding of the German Metrology Institute (PTB) and support of the SPIN project, a proficiency testing scheme for cement testing according to EN 196 was set up for African laboratories. Proficiency testing schemes, also called round robins, are inter-laboratory performance comparisons allowing participants to evaluate themselves against pre-established criteria. They are a powerful tool to help laboratories improve their performance as well as demonstrate their competences to accreditation bodies or customers. 26 laboratories from 20 nations, 18 of which from Africa, participated. The BAM Federal Institute for Materials Research and Testing acted as coordinator and provider of the scheme. The aim of the round robin was to interpret the submitted data further beyond the pure statistic analyses. The data provided a positive picture of the performance of the participants in general, but it also exhibited a number of technical fields that need improvement. The paper provides the general results of the scheme and analyses identified strengths and weak points based on the submitted and non submitted data as well as on discrepancies from the EN 196 procedures during measurements. The application of EN standards for material testing is critically discussed and since quality infrastructure is also always an issue between industrial and political stakeholders, suggestions for the mitigation of the identified shared problems are given. KW - Round robin KW - Quality control KW - Cement testing KW - Proficiency testing PY - 2013 SN - 2225-0514 SN - 2224-5790 VL - 4 SP - 54 EP - 58 PB - International Institute for Conservation of Historic and Artistic Works CY - New York, NY, USA AN - OPUS4-29933 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Leinitz, Sarah ED - Diouri, A. ED - Boukhari, A. ED - Ait Brahim, L. ED - Bahi, L. ED - N., Khachani ED - Saadi, M ED - Aride, J. ED - Nounah, A. T1 - Concrete casting robustness improvement due to active rheology N2 - With ongoing innovation in process technology, the challenges of concrete technology are more and more focused on the rheological optimisation for these processes, since improper mixture stability or poor compaction ability negatively affect the concrete homogeneity and quality. However, along with the increasing complexity of today’s concrete mixture compositions, concrete becomes more prone to failure regarding the casting process. Variable properties of the raw materials typically cause changing workability. The reasons can be found among others in scattering water contents, physical or chemical properties of the cement or varying environmental temperatures. Robustness in the delicately adjusted rheology, however, is of utmost importance for modern and future process technology, from sprayed concrete over pumpable concrete towards 3D-printing, with regard to the long-term strength, the function and the durability. Typically, material induced changes cannot be identified easily due to the complex interactions of concrete constituents. Therefore, a precise and prompt counteraction is impossible. However, it is known that the yield stress can be controlled by addition of supplementary superplasticizer or stabilising agent. In combination with computerized process observation tools that can rapidly interpret and react on changes in the rheology, it is therefore thinkable, that only these two admixture types can adjust the rheology steadily and permanently, regardless of the actual root cause for observed macroscopic rheology change. The presentation will firstly give a comprehensive overview of effects at the interface between pore solution, particles and hydrates, which affect the rheology of fresh concrete. Secondly, ways are recommended how the rheology can be actively manipulated before eventually computerized methods are demonstrated that help to actively and rapidly assess and counteract performance scatter during steady casting processes. T2 - 2nd International Congress on Materials & Structural Stability (CMSS-2017) CY - Rabat, Morocco DA - 22.11.2017 KW - Cusum KW - Rheology KW - Control Chart KW - Concrete KW - Robustness PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-444317 DO - https://doi.org/10.1051/matecconf/201814901001 SN - 2261-236X VL - 149 SP - 01001-1 EP - 01001-7 PB - EDP Sciences CY - Les Ulis AN - OPUS4-44431 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - 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 T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 2013-01-28 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 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 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten ED - Khayat, Kamal Henry T1 - Cusum charts for the control of the slump flow of self-compacting concrete in a steady production process N2 - Control chart systems are commonly used in quality management systems to keep production processes stable. The most efficient control chart systems are cumulated sums (cusum), which look at the deviations from a target value. Cusum charts react more rapidly on systematic changes in processes than other charts such as Shewhart charts, which look at the process values. The cusum method is often applied for compressive strength but it is particularly suitable if counteractions be taken immediately, like in the case of fresh concrete properties. The present study shows that regardless of the manipulation, 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 V-mask indicates a systematic change. A reference SCC was artificially manipulated in order to achieve either increased or reduced flowability. Arithmetic mean values and standard deviations were determined experimentally without and after taking counteractions. These parameters were used for case studies of steady SCC productions based on normally distributed random values. For the indication of a systematic change, a standard V-mask was used. The results point out that productions with applied cusum methods were capable of keeping the slump flow deviation from the target in the order of magnitude of about 1% despite drastic manipulations, while productions without applied cusum method deviated up to 14% and more from the target slump flow value. T2 - 8th RILEM Symposium on Self-Compacting Concrete CY - Washington, USA DA - 15.05.2016 KW - Control charts KW - Cusum KW - Quality control KW - Rheology KW - Self-compacting concrete PY - 2016 SN - 978-2-35158-157-5 SP - 283 EP - 294 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-36874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram T1 - Der Siebtrennversuch nach prEN 12350-11 KW - SCC KW - SVB KW - Prüfverfahren KW - Sedimentation KW - Siebtest KW - EN 12350-11 PY - 2007 SN - 0005-9846 VL - 57 IS - 10 SP - 448 EP - 454 PB - Verlag Bau + Technik CY - Erkrath AN - OPUS4-16148 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 - 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 - Ramge, Peter A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - Effect of the storage of cement on early properties of cementitious systems N2 - As soon as cement is mixed with water, the hydration reaction starts to set of. The progression of the hydration process is governed by the amount and the availability of water and its possibility to access the unhydrated cement grain surfaces. For a total hydration cement theoretically requires water amounting approximately 0.38 of its own mass. Nevertheless, due to the cement’s highly hygroscopic nature, already the moisture in the ambient air can cause first hydration reactions to set in upon the cement grain surfaces. Such pre-hydration processes have an effect on the cement's properties. Dpending on the specific conditions during the storage the significance of the impact on certain properties can vary. If cement is consumed soon after production and is transported only short distances in a silo wagon to its final destination for immediate use without further stock transfer, the effects are rather negligible. However, if cement is delivered in bags, transported over long distances, shifted serval times and stored for longer time periods until it is finally consumend, these effects can be quite severe. Due to the actual logistical situation with comparably few cement plants, large delivery distances and partially less developed infrastructures, the latter scenario pictures the situation for the most cases in Africa quite well. In order to verify the relevance of the pre-hydation for practical application, a series of tests was conducted at the German Federal Institute for Materials Research and Testing (BAM). The influence of the cement storage on gresh and hardened concrete properties was investigated for different concrete and mortar types. The investigations show that the impact of the storage conditions is more pronounced for specialized concretes with high sophisticated optimized mixture compositions containing admixtures. Nevertheless, the effects also occur for ordinary concrete and should not be ignored. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 KW - Cement KW - Storage KW - Ambient conditions KW - Hydration KW - Pre-hydration KW - Atmospheric humidity PY - 2013 SN - 978-3-9815360-3-4 SP - 339 EP - 347 AN - OPUS4-27757 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vasiliou, Eleni A1 - Schmidt, Wolfram A1 - Stefanidou, Maria A1 - Kühne, Hans-Carsten A1 - Rogge, Andreas ED - Amziane, Sofiane ED - Sonebi, Mohammed ED - Charlet, Karine T1 - Effectiveness of starch ethers as rheology modifying admixtures for cement based systems N2 - Polysaccharides are important rheology modifying admixtures in the building material sector. The use of starch is becoming increasingly important, due to many ecological and economic advantages. In the construction sector, starch ethers are being used as thickeners and as means to increase the yield stress. The starch ethers that are available on the market differ in their behaviour, which can vary greatly depending upon the binder system and mortar composition, e.g. solid volume content, binder type, additional admixtures. In view of the limited knowledge about the influence of molecular modifications associated with cement based systems, some fundamental rheological functional mechanisms were analysed in this study. The differently modified starch ethers used were derived from potatoes. They varied in their charges and degrees of hydroxypropylation. The setting and the flow behaviour of all examined variations of starch ethers were analysed in cement pastes. In order to illustrate the effects of the starch ethers that were used, the water-cement ratio (w/c) was held constant in all the mixtures [Schmidt 2012]. The results indicated significant differences in setting and flow behaviour. T2 - Second International RILEM Conference on Bio-based Building Materials CY - Clermont-Ferrand, France DA - 21.06.2017 KW - Rheology KW - Polysaccharides KW - Cement KW - Concrete KW - Starch KW - Polycarboxylate PY - 2017 SN - 978-2-35158-192-6 SP - 81 EP - 85 PB - RILEM S.A.R.L CY - Paris, France AN - OPUS4-43548 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 - GEN A1 - Schmidt, Wolfram A1 - Brouwers, J. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Khayat, K. H. ED - Feys, D. T1 - Effects of superplasticizer and viscosity-modifying agent on fresh concrete performance of SCC at varied ambient temperatures N2 - Varying ambient temperatures in plants or on construction sites during casting of SCC can cause serious problems affecting the fresh concrete performances, such as rheological properties and setting time, with consequences for the hardened properties in the structure. By sensible choices of the components, the robustness of SCC mixtures against temperature variations can be improved. However, this aspect has not been the focus of intensive research yet. In this study the effects of varied ambient temperatures on the early performance of differently composed SCC mixtures are investigated, with emphasis on changes in rheology, early deformations, heat evolution and setting. Focus is placed on the study of the influence of the polycarboxylate ether molecule type as well as different viscositymodifying agents on the temperature robustness. Effects on the relevance for practical concrete applications are evaluated, which will provide a reliable framework of possible actions on the appropriate use of admixtures for SCC. T2 - SCC 2010 - 6th International RILEM Symposium on self-compacting concrete / 4th North American conference on the design and use of SCC - Desgin, Production and Placement of self-consolidating concrete CY - Montreal, Canada DA - 2010-09-26 KW - Polycarboxylate KW - Modified starch KW - Rheology KW - Self-compacting concrete KW - Temperature KW - Yield stress KW - Viscosity PY - 2010 SN - 978-90-481-9663-0 DO - https://doi.org/10.1007/978-90-481-9664-7_6 N1 - Serientitel: RILEM bookseries – Series title: RILEM bookseries VL - 1 IS - 2 SP - 65 EP - 77 PB - Springer AN - OPUS4-22126 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Effects of the characteristics of high range water reducing agents and the water to powder ratio on rheological and setting behavior of self-consolidating concrete N2 - To design robust self-consolidating concrete (SCC) for various environmental conditions, it is essential to understand the relevant mechanisms that control the flow performance. This paper depicts how high range water reducing agents (HRWRAs) interact with clinker and hydration phases, and it discusses the important role of the charge density of polycarboxylic HRWRAs in the way the rheology is affected. Based on the rheometric investigations on SCC mixture compositions with different water to powder ratios (w/p) and observations of their pastes' Vicat setting times, the study shows that increasing charge densities of the HRWRA and decreasing w/p reduce the flow retention and have lesser retarding effect on the setting. Based on the test results and discussions optimization procedures for the mixture composition and the HRWRA modification are suggested to achieve optimized performance for varying environmental situations and highest robustness for specific conditions. KW - Polycarboxylate KW - HRWRA KW - Robustness KW - Rheology KW - Self-consolidating concrete PY - 2014 DO - https://doi.org/10.1520/ACEM20130094 SN - 2165-3984 VL - 3 IS - 2 SP - 1 EP - 15 PB - ASTM International CY - West Conshohocken, Pa., USA AN - OPUS4-30388 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 A1 - Wend, Dirk A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Einfluss der Fließmittelmdoifikation auf Prozesse während der frühen Hydratation von selbstverdichtenden Bindemitteln KW - Rheologie KW - Frühe Zementhydratation KW - Polycarboxylatether KW - Vicat KW - Schwinden PY - 2012 SN - 1439-7706 VL - 4 SP - 66 EP - 71 PB - ad-media-Verl. CY - Köln AN - OPUS4-26356 LA - deu 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 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 - 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 - 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? 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 -