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 - 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 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 - 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 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 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 - 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 - 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 - 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 - 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 - 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 -