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 - CONF A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, I. L. A1 - Mbugua, R. A1 - Olonade, K. A. ED - Greim, M. ED - Kusterle, W. ED - Teubert, O. T1 - Natural rheology modifying admixtures for concrete N2 - The possibility to tailor the rheology of concrete eventually opened up the path to new technologies, where design criteria are no longer limited to the compressive strength. Thus, it can be concluded that the capability to control the rheology of concrete can be considered as catalyst for many of today’s concrete innovations. In the same way rheology modifying admixtures will be key to mastering the challenges of the next decades. In many regions of the Southern hemisphere, the effective use of chemical admixtures would significantly contribute to solve problems induced by the challenging climate, but particularly in Africa there is often a lack of local supply and supply infrastructure. In Africa, concrete admixtures are largely shipped or transported from outside the continent. The long distance transportation of chemicals is not very environmentally friendly and the economic consequences are dramatic: the agents are difficult to purchase, expensive, and there is no large variety of products available in the market. Due to the enormous relevance of rheology modifying admixtures, it is worthwhile to recollect that nature provides an enormous variety of chemicals that can be used readily or with low processing and without enormous transportation distances, since these plants are typically regionally abundantly available, cheap, and they are environmental friendly. The paper presents an overview of various options for rheology modifying admixtures, that can be found in Africa, and that may become a real alternative, once their interaction within the complex cementitious system is well understood. T2 - 26. Workshop und Kolloquium "Rheologische Messungen an Baustoffen" CY - Regensburg, Germany DA - 21.02.2017 KW - Concrete KW - Rheology PY - 2017 SN - 978-3-7439-0171-1 SP - 75 EP - 87 PB - tredition GmbH CY - Hamburg AN - OPUS4-40599 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 U6 - http://nbn-resolving.de/urn/resolver.pl?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 - 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 - Mota Gassó, Berta A1 - Sturm, Heinz A1 - Pauli, Jutta ED - Greim, M. ED - Kusterle, W. ED - Teubert, O. T1 - Influence of effects on nano and micro scale on the rheological performance of cement paste, mortar and concrete 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 such as self-compacting concrete. Today, admixture addition has become common practice in concrete technology, but the understanding of their highly complex mode of operation is extremely difficult and demands for understanding of processes within the range between nanometres and centimetres. 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. Methods are discussed that appear promising interdisciplinary tools for enhancement of the understanding of the relevant interactions that are responsible for the macroscopic flow of flowable concrete. T2 - 25. Workshop und Kolloquium Rheologische Messsungen an Baustoffen CY - Regensburg, Germany DA - 02.03.2016 KW - Rheology KW - Cement KW - Concrete KW - Superplasticizer KW - Nano scale PY - 2016 SN - 978-3-7345-1313-8 SP - 294 EP - 307 PB - tredition CY - Hamburg AN - OPUS4-36862 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 - 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 - 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 - 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 - 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-444317 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 -