TY - CONF A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Improvement of durability of SCC by the use of micro fly ash and limestone filler T2 - BAM-Präsentation Nanocem-Meeting CY - Copenhagen, Denmark DA - 2006-04-25 PY - 2006 AN - OPUS4-12475 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 - The influence of superplasticiser modifications on early hydration processes N2 - Self-compacting concrete (SCC) differs substantially from normal concrete as regards the quantity of superplasticiser dosage. The functionality of superplasticisers, based on the polycarboxylate ether (PCE) superplasticiser customary with SCC, is nowadays very well understood at construction material research level. However, knowledge concerning pertinent correlations does not always permeate practice to an equal extent. PCEs are extremely polymorphic as opposed to earlier superplasticiser groups, which still possess a considerable proportion of the superplasticiser market. The geometry of polymers can be adjusted individually to performance characteristics required for certain uses. Yet, in selecting a superplasticiser for its specified rheological properties, a very strong influence can equally be exerted simultaneously on the subsequent hydration process. The charge density of the PCE employed also plays a key role in connection with both rheology and early hydration. KW - Rheology KW - Early cement hydration KW - Polycarboxylate ether vicat KW - Shrinkage PY - 2012 SN - 1437-9023 VL - 4 SP - 64 EP - 69 PB - ad-media-Verl. CY - Köln AN - OPUS4-26355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten ED - Rogge, A. ED - Meng, B. T1 - Cement and concrete development in Africa: the role of the SPIN project T2 - 52. DAfStb-Forschungskolloquium CY - Berlin, Deutschland DA - 2011-11-07 PY - 2011 SN - 978-3-9814281-0-0 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 339 EP - 344 PB - BAM Bundesanstalt für Materialforschung und -prüfung CY - Berlin AN - OPUS4-25172 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Kühne, Hans-Carsten T1 - SPIN- Spearhead network for innovative,clean and safe cement & concrete technologies N2 - Worldwide, cement and concrete experts are at the cutting-edge to sustainable, green, healthy but nonetheless high-Performance concrete. The current relatively low development of the cement and concrete industry in Africa offers the unique opportunity to start directly on the best achievable and sustainable Level, if only Expertise is sufficiently available. It should not be neglected that concrete is a product with comparably low Transport ranges, which means that an improved concrete market will mainly Support the local economy without exceeding financial Drains to the international market, thus fostering the fight against poverty, which is an urgent Need in most African countries. T2 - Workshop Cement and Concrete for Africa CY - Berlin, Germany DA - 17.08.2011 PY - 2011 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-24728 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kühne, Hans-Carsten A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Uzoegbo, H. C. T1 - Building practice and concrete infrastructure development in eastern and southern Africa N2 - The construction sector has traditionally been a source of employment in African regions. However, due to policy changes, cut backs in public investments as well as a fall in the number of employments in the private sector have been observed in many countries. Furthermore a shift from registered companies to informal contractors could be noticed. Many contractors offer services they do not provide permanently or for which the required equipment has to be borrowed. A study that was published in 2000 about the situation in Tanzania pointed out that only ca. 15% of the enterprises that offer concrete works own a concrete mixer. The building practice with concrete varies widely over the African continent. Whereas the level of technology and the infrastructure for cement and concrete in South Africa is elaborate, in East Africa and particularly those that were heavily suffering from civil war during the nineties of the last century, the availability of cement and concrete is poor and these materials are far from being everyday building practice. Most of the population relies on indigenous forms of construction requiring wood obtained from felling of forest trees and ultimately contributing to de-forestation. Informal settlements in South-Africa and Kenya are literal evidence where originally green natural vegetation has been turned into artificial desert-like landscapes. PY - 2011 SN - 1437-9023 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 3 SP - 32 EP - 37 PB - ad-media-Verl. CY - Köln AN - OPUS4-25360 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Challenges of the African environmental conditions for concrete mixture composition N2 - Concrete technology was exposed to a rapid development during the last three decades. For the longest time in its history, concrete was considered as a three component System consisting of aggregates, which are bound by the hardened cement paste consisting of hydrated cement. Traditionally, the only way of adjusting the consistency of concrete was using well adjusted aggregates and grading curves and adding excess water to the concrete, accepting that the latter in return reduces strength and durability. During the last three decades, however, concrete has developed further from a three component System towards an (at least) five component system, since the use of mineral additions and Chemical admixtures has become state of the art. Both components are able to enhance the workability, the compactability, and the density of the microstructure with effects on strength, ductility and durability, while cement can be saved in parallel. Due to reasonable use of admixtures and additions, concrete can be designed to match mechanically high performance specifications. Traditionally, cement paste was considered the weakest component in concrete. Flowever, in modern concrete a good paste composition can yield highest performance, passing the role of the mechanical bottleneck towards the aggregates. T2 - Workshop cement and concrete for Africa CY - Berlin, Germany DA - 17.08.2011 KW - Cement KW - Concrete KW - Mixture composition KW - Africa KW - Climatic conditions PY - 2011 SN - 978-3-9814281-4-8 SP - 37 EP - 49 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-24780 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - The SPIN project N2 - Globally, cement and concrete experts are at the cutting-edge to sustainable, green, healthy but nonetheless high-performance concrete. In the present age, concrete is not yet well established in Africa, which öfters the unique opportunity to build up a cement and concrete market based on the highest available state of technology. As this industry needs high level expertise, a central issue in implementation of skilled technology is cross-linking research institutions and laboratories. It should not be neglected that concrete is a product with comparably low transport ranges, which means that an improved concrete market will mainly support the local economy without exceeding financial drains to the international market, thus fostering the fight against poverty, which is an urgent need in most African countries. The SPIN project highlights recent developments in the field of cement and concrete research with impact on the local and global economy. Challenges, future developments and opportunities for the African construction industry are in the focus. The SPIN project is funded by the European Commission (EC) and supported by the African, Caribbean and Pacific (ACP) Group of States under the project body of the ACP Science and Technology Programme. SPIN is acronym for “Spearhead network for Innovative, Clean and Safe Cement and Concrete Technologies”. The project aims to cross-link experts with industry and policy making bodies, aiming to establish sustainable cement and concrete construction in Africa. T2 - Workshop cement and concrete for Africa CY - Berlin, Germany DA - 17.08.2011 PY - 2011 SN - 978-3-9814281-4-8 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 5 EP - 9 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-24778 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 - 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 - Schmidt, Wolfram A1 - Uzoegbo, H.C. A1 - Priebe, Nsesheye Susan A1 - Kühne, Hans-Carsten A1 - Rogge, Andreas ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - Experiences in an African-European-cooperation project: strengthening research capacity in cement and concrete in Africa N2 - This report is based on a three-year experience as coordinator of the ACP-EU funded SPIN project. The project involved eight African and three European partners. Practical and unforeseeable problems are addressed that occurred during the project implementation and ways how they were successfully solved are reported. The major problems in many African institutions were administrations that are not used to work in multi-national consortia and a lack of institutional support for the African researchers. In Europe a misjudgement of the African boundary conditions as well as inflexible administrations caused problems. Finally the funding scheme did not always allow to easily overcome the high number of unexpected practical problems. A major deficit identified during the project was a general trend in Africa to underestimate the role of research for the development of the continent. Most universities focus on teaching applied sciences, which is without doubt important to cover the market need for qualified staff in the rapidly growing African industries. However, this makes it unattractive for highly qualified performers to conduct research on the continent. Furthermore this leads to the situation that the curricula can only contain second hand knowledge. In order to attract international high level researchers, it is suggested to install multi-national regional excellence research centres that only promote PhD and post-doc research on a level that can cope with highest international excellence. High level research is often perceived as not capable of focusing on immediate actual problems that many African economies have to cope with.. However, it is considered to be very sustainable in terms of autonomy and mastering future challenges. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 PY - 2013 SN - 978-3-9815360-3-4 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 1177 EP - 1184 AN - OPUS4-27762 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Kühne, Hans-Carsten ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - Rheological optimisation for flowable mixture compositions specified for African boundary conditions N2 - To date concrete technology is not yet well established in sub-Saharan Africa but considering the construction technological challenges of the region, without doubt, concrete will play a major role in future. The social, economic, and geographic boundary conditions distinguish greatly from those that can be found in many other regions of the world, where concrete is considerably well established. Düring the last decades, concrete technology underwent a rapid evolution process, but in most countries, where concrete is already well established, innovations are difficult to be brought into practice, Africa, currently has the opportunity and potential, of directly establishing the best available practice in concrete technology. The conclusion is drawn that self-compacting concrete (SCC) or highly flowable concrete is a reasonable solution for African construction sites. Since on most African construction sites the disadvantageous concreting environment is the most crucial factor for the concrete quality, the outstanding workability properties outweigh any disadvantages of SCC. Based on this consideration, concepts are developed, how to bring about robust SCC cost-efficiently and reliably into practice as pre-mixed dry compound under consideration of local materials such as rice husk ashes, bagasse ashes, natural pozzolans, cassava starch and lignosulphonate. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 KW - Mixture composition KW - Rheology KW - Climatic conditions KW - Admixtures KW - Additions PY - 2013 SN - 978-3-9815360-3-4 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 359 EP - 366 AN - OPUS4-27764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kumaran, G.S. A1 - Priebe, Nsesheye Susan A1 - Schmidt, Wolfram A1 - Florea, M.V.A. A1 - Nibasumba, P. ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - A study on sustainable energy for cement industries in Rwanda N2 - Rwanda is a landlocked country in the East Africa. It is surrounded by Uganda, Tanzania, Congo and Burundi. Rwanda is a fast developing country and it spends most of its revenues to import fossil fuels from either through Mombasa Port in Kenya or Dar es Salaam port in Tanzania because the energy production in Rwanda is not sufficient for its development. Transporting the fuels from these ports, add on to the cost of all materials, cement industry being no exception. There are three cement companies in Rwanda. The cement industries could not run in full production due to the shortage of fuel. Moreover, Rwanda is importing all the construction materials such as steel, roofing materials, etc from its neighbouring countries. This increases the cost of construction and the common man find difficult to own a house. In order to sustain the energy needs of Rwanda, different sources of energies should be focused. They are Peat, Geothermal, Methane gas, solar, wind, waste materials and Municipal wastes. Without affecting the environment, there is an urgent need to find a solution on sustainable energy in Rwanda. This paper discusses about the possible sources of energy in Rwanda which will improve the energy sustainability and turn the economy of Rwanda. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 KW - Biomass KW - Cement production KW - Peat KW - Energy sustainability PY - 2013 SN - 978-3-9815360-3-4 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 1169 EP - 1175 AN - OPUS4-27766 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Radlinska, A. A1 - Nmai, C. A1 - Buregyeya, A. A1 - Lai, W.L. A1 - Kou, S. ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - Why does Africa need African concrete? An observation of concrete in Europe, America, and Asia - and conclusions for Africa N2 - Portland cement, as we know it today, has its origin in Great Britain approximately 170 years ago. Since then, concrete technology has spread out to Europe, the United States, and Japan, where it became a key component for rapid industrial development. Europe, the Unites States and many Asian countries today have developed a high level of technology regarding concrete construction. However, each of them has a unique history and as a result, different “concrete philosophy” depending upon the social, environmental and financial boundary conditions, as well as their evolution throughout the years and local construction traditions. As a result, the word concrete may refer to rather different materials in America, Europe, and Asia. Apart from South Africa, most sub-Saharan African countries cannot look back on a similarly long cement and concrete history. Cement and concrete are rather new materials and not yet well established. This gives African engineers the unique opportunity to learn from past mistakes and to develop a concrete technology, which refers to the best available practice. However, in many sub-Saharan African countries, standards and regulations are adopted (preferably from Europe or the US) without consideration of the historical background of these standards. Although this practice helps saving resources for the implementation, it does not necessarily yield the best result in the African environment, and also from an economic point of view it might come back disadvantageously due to unnecessary overdesigning. By comparing the differing states-of-the-art in North America, Europe, and Asia, this paper emphasizes, how regional conditions determine the practice of concrete technology in the sub-Saharan area. It is therefore important for Africa to develop a unique African concrete technology, which is perfectly fitted to the specific local conditions, even if it may vary distinctively from the established practice elsewhere. The paper concludes that African nations should effort into adapting existing principles that have proved to function well rather than adopting existing standards. 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 - Casting environment KW - Concrete KW - Durability KW - Standards PY - 2013 SN - 978-3-9815360-3-4 SP - 1139 EP - 1147 AN - OPUS4-27767 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 - 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 - Schmidt, Wolfram T1 - Influence of the processing temperature and combined admixtures on the properties of Self-Compacting Concrete T2 - 7th International PhD Symposium in Civil Engineering CY - Stuttgart, Germany DA - 2008-09-11 PY - 2008 IS - Kap. 16.8 SP - 75 EP - 84 AN - OPUS4-17948 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Performance and interactions of admixtures for SCC exposed to different climatic conditions T2 - CONSEC'07 Tours Concrete under Severe Conditions, CY - Tours, France DA - 2007-06-04 PY - 2007 AN - OPUS4-14874 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Toutlemonde, F. ED - et al., T1 - Performance and interactions of admixtures for SCC exposed to different climatic conditions T2 - Fifth International Conference on Concrete under Severe Conditions: Environment and Loading (CONSEC `07) CY - Tours, France DA - 2007-06-04 PY - 2007 SN - 1628-4704 VL - 2 SP - 979 EP - 986 CY - Tours, France AN - OPUS4-15050 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Temperature related effects on self-consolidating concrete due to interactions between superplasticizers, supplemental admixtures and additions T2 - 9th ACI International conference on superplasticizers and other chemical admixtures in concrete CY - Seville, Spain DA - 2009-10-12 KW - Polycarboxylate KW - Modified starch KW - Rheology KW - Self-compacting concrete KW - Temperature KW - Setting KW - Shrinkage KW - Heat evolution PY - 2009 SN - 978-0-9731507-8-0 SP - 135 EP - 147 AN - OPUS4-20884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - 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 U6 - 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 - Uzoegbo, H.C. A1 - Bjegovic, D. A1 - Schmidt, Wolfram A1 - Kitobo, W. T1 - SCM potential in Africa KW - Africa KW - Cement KW - Supplementary cementitious materials PY - 2012 SN - 0263-6050 SN - 0308-8855 IS - August SP - 27 EP - 38 PB - Swan CY - Leatherhead AN - OPUS4-27176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Kumaran, G.S. T1 - Clearing the way KW - Cement KW - Concrete KW - Africa KW - Research policy PY - 2012 SN - 0959-6038 IS - October SP - 86 EP - 88 PB - Holbrook & Son CY - Dorking AN - OPUS4-27177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barthel, Maria A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram ED - Bager, D. H. ED - Silfwerbrand, J. T1 - Multilayer concrete pavers - solutions for the mitigation of the urban heat island effect N2 - The large scale application of self-cooling concrete pavers is a future-oriented approach to reduce the urban heat island effect in inner-city areas. Making use of evaporation enthalpy, these new pavements counterbalance the absorption of solar radiation and the subsequent transfer of heat to the surrounding environment. The concrete pavers consist of a permeable top-layer and a storage layer. As the different requirements of these layers demand different concrete mixtures they are developed and optimised for their respective functions. This paper presents some results of the concrete mixture design and Solutions that combine a sufficient compressive strength as well as good water transportation properties for the face concrete layer. T2 - fib Symposium Stockholm 2012 'Concrete structures for a sustainable community' CY - Stockholm, Sweden DA - 11.06.2012 KW - Urban heat island effect KW - Concrete multilayer pavers KW - Permeability KW - Fibre concrete PY - 2012 SN - 978-91-980098-1-1 SP - 513 EP - 516 PB - Royal Institute of Technology CY - Stockholm AN - OPUS4-27271 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Roussel, N. ED - Bessaies-Bey, H. T1 - A simple test method to assess the influence of PCEs on the rheology of flowable cementitious systems N2 - Today’s superplasticizers for self-compacting concrete and high Performance cementitious materials are very versatile. Typically superplasticizers are composed of a polycarboxylic backbone equipped with polyethylene oxide graft chains of variable length and grafting degree. The mode of operation of these admixtures is based on the steric repulsion of the particles upon adsorption. The adsorption is strongly depending upon the charge density of a superplasticizer and the time dependent Adsorption processes control the retention of the flow performance – an important issue particularly for ready-mix and construction site concrete. However, the properties of polycarboxylic superplasticizers typically remain a black box for users. The paper suggests a simple and rapid test method, which can be conducted without sophisticated equipment, to qualitatively distinguish between two types of superplasticizers based on the adsorption mechanism. Interpreting the results in the right way provides a powerful tool to choose the right admixture for individual time dependent flow specifications. T2 - 1st international RILEM conference on rheology and processing of construction materials and 7th RILEM conference on self-compacting concrete CY - Paris, France DA - 02.09.2013 KW - Adsorption KW - Polycarboxylate ether KW - Rheology KW - Slump flow PY - 2013 SN - 978-2-35158-137-7 IS - Chapter 2.1.1 SP - 1 EP - 8 AN - OPUS4-29929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Barthel, Maria A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten T1 - Mitigation of the urban heat island effect by self-cooling concrete pavers N2 - Worldwide an increasing migration from rural to urban regions can be observed. Hence cities are growing and as a result the building density and the land sealing rise. Concrete as commonly used building material in urban structures provides a high heat storage capacity. Therefore the microclimate in cities has become warmer than in the surrounding areas. This phenomenon is called Urban Heat Island Effect. To mitigate this situation a large scale application of self-cooling concrete pavers is an approach to reduce the urban heat island effect. Making use of evaporation enthalpy, this new type of pavements counterbalances the absorption of solar radiation and the subsequent transfer of heat to the surrounding environment. The typical double-layer structure of concrete paving stones can be maintained. The mass concrete acts as a water storage layer and is covered by a permeable face concrete. As the different requirements of these layers demand different concrete mixtures, they are developed and optimised for their respective functions. This paper presents some suitable no-slump concrete mixtures that combine a sufficient compressive strength as well as good water transportation properties for the above mentioned approach. KW - Pavement KW - Urban heat island KW - No slump concrete KW - Fibers PY - 2013 SN - 2225-0514 SN - 2224-5790 VL - 4 SP - 35 EP - 39 PB - International Institute for Conservation of Historic and Artistic Works CY - New York, NY, USA AN - OPUS4-29931 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 ED - Schmidt, W. ED - Uzoegbo, H. T1 - Peculiarities of African cement and concrete markets - Challenges and opportunities N2 - The African environment for the construction with concrete differs greatly from the Situation that can be found in Europe, Japan or North America. Europe can look back upon a concrete tradition of more than 150 years. Standardising documents and guidelines exist since more than 100 years, which formed the foundation of modern Standards that are adopted and applied and in many regions of the world. The technological developments in cement production are also strongly influenced by environmental conditions of the Northern hemisphere. In contrast, with the exception of South Africa, in most countries of sub-Saharan Africa, cement production started in the 1950s to 1960s, followed by a period of political and economical disturbances in many countries. As a result, there have not been serious approaches towards customised Solutions for the construction with concrete for the specific boundary conditions of sub-Saharan Africa. In most countries Standards from overseas are applied. Today, most African economies are growing at a rapid pace and construction activities in infrastructure and housing are urgently required to support and keep up the economic verve. Concrete technology will become of major interest in this context, since no other material can be produced similarly efficiently based on raw materials, which can be found largely only locally. In order to produce concrete with high efficiency, the local boundary framework has to be taken into account. Sub-Saharan Africa exhibits special peculiarities that are not covered by the recently applied technological guidelines and Standards. These need to be addressed to in local codes of practice in order to maximise the benefit of concrete technology. T2 - Bauma Africa 2013 - Global issues in concrete construction - Markets, perspectives, technologies CY - Johannesburg, South Africa DA - 18.09.2013 PY - 2013 SP - 25 EP - 28 AN - OPUS4-30032 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Sonebi, M. A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Diouri, A. ED - Khachani, N. ED - Alami Talbi, M. ED - Ait Brahim, L. ED - Bahi, L. T1 - Rheology modifying admixtures: The key to innovation in concrete technology - a general overview and implications for Africa N2 - Innovative admixture technology has significantly widened up the ränge of possibilities of concrete engineers. For many decades the water to cement ratio (w/c) was the major influencing factor for the performance of concrete. Due to the need to adjust a consistency, which still allowed reasonable workability, the w/c was typically significantly higher than technologically reasonable. Rheology modifying admixtures Support adjusting the concrete consistency largely independent of the w/c. It was only after the invention of the first superplasticizers that modern concrete technology significantly evolved in terms of flowability, strength, and durability, and only due to the steady evolution of the technology modern innovations, such as Self-Compacting Concrete, Ultra-High-Performance Concrete, or Engineered Cementitious Composites were made possible. Today’s superplasticizers are extremely versatile and can be adjusted to individual technological specifications. However, the other side of the coin of versatility is that cementitious Systems incorporating superplasticizers have become more sensitive against environmental influences, such as the environmental temperature, which may cause unwanted effects or demand for supplementary admixture use such as stabilizing admixtures. Hence, concrete mixture composition with admixtures demands for a high level of expertise and offen there is lack of awareness about the mode of Operation of rheology modifying admixtures among concrete technologists. The paper gives a comprehensive overview about rheology modifying admixtures such as superplasticizers or stabilizing agents, and how they can be used depending upon the application in the most favourable way. Based on experiences with the sub-Saharan African concreting boundary conditions, which exhibit many challenges in terms of environmental boundary conditions and construction site logistics, conclusions are finally drawn, how admixtures can be used in the most beneficial way to improve the concrete casting Situation. T2 - CMSS 2013 - International congress on materials & structural stability - Building up sustainable materials & constructions CY - Rabat, Morocco DA - 27.11.2013 KW - Rheology KW - Superplasticizers KW - Stabilising agents PY - 2013 SN - 978-9954-32-689-3 SP - 1 EP - 6 AN - OPUS4-30040 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sonebi, M. A1 - Khatib, J. A1 - Schmidt, Wolfram ED - Diouri, A. ED - Khachani, N. ED - Alami Talbi, M. ED - Ait Brahim, L. ED - Bahi, L. T1 - Influence of the type of viscosity-modifying admixtures and metakaolin on the rheology of grouts N2 - The Viscosity-modifying admixtures (VMAs) contribute to the control of the rheology of grouts and are used to enhance plastic viscosity, cohesion, stability, and resistance to bleeding of cement-based systems. This paper reports the results of an investigation on the effect of type of VMAs, namely two types of diutan gums and a welan gum and metakaolin (MTK), plus a superplasticiser, on the rheology behaviour of cement grouts. All mixes were made with polycarboxylic superplasticiser at 0.6% and 0.9%. The dosages of VMAs were 0.05%, and 0.10%, with a fixed water-to-binder ratio of 0.40. The investigated fresh properties of the grouts included the mini-slump flow, plate cohesion, and rheology parameters: namely yield value and plastic viscosity. The rheological parameters were obtained using a vane viscometer. Control grouts (with and without superplasticiser and VMA) were also tested and compared to mixes containing VMAs. The results indicated that the incorporation of MTK reduced the fluidity and increased the plate cohesion and yield stress, and plastic viscosity due to the higher surface area of MTK. The diutan gum grouts improved the grout fresh properties and rheology compared to the welan gum grouts. 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 - 6 AN - OPUS4-30041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - CONF A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Interactions between PCE and different polysaccharides and influences on the early hydration of cement N2 - ln order to observe the influence of stabilising agents (STA) based on starch and diutan gum, rheometric experiments and setting tests were conducted on cement pastes with and without PCE superpiasticizers. The results show that with regard to yield stress both STAs show differing behaviours in Systems without PCE. In presence of PCE, yield stress infiuences of the STAs retreat into the background. The Vicat results exhibit that STAs can reduce the retard ing effect of PCE. T2 - 1st International conference on the chemistry of construction materials CY - Berlin, Germany DA - 07.10.2013 PY - 2013 SN - 978-3-936028-75-1 N1 - Serientitel: GDCh-Monographien – Series title: GDCh-Monographien VL - 46 SP - 49 EP - 52 AN - OPUS4-30045 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bintz, Thilo A1 - Munsch, Sarah Mandy A1 - Stelzner, Ludwig A1 - Lauinger, Robert A1 - Schmidt, Wolfram A1 - Kruschwitz, Sabine T1 - An NMR tomograph for building materials - applications, experimental studies and limitations - N2 - A summary of the possibilities, technical limitations and application examples for a unique NMR tomograph at BAM. T2 - 13th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances (ISEMA), 2021 CY - Kiel, Germany DA - 27.06.2021 KW - Relaxation time distribution KW - NMR imaging KW - Capillary suction PY - 2021 SN - 978-1-7281-8738-9 N1 - Geburtsname von Munsch, Sarah Mandy: Nagel, S. M. - Birth name of Munsch, Sarah Mandy: Nagel, S. M. SP - 106 EP - 110 PB - IEEE AN - OPUS4-53116 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 - 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 - 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 A1 - Weimann, Christiane A1 - Chaves Weba, Luciana ED - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - Influences of hydration effects on the flow phenomena of concrete with admixtures 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 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa CY - Dar es Salaam, Tanzania DA - 27.01.2016 KW - Cement hydration KW - Polymer adsorption KW - Rheology KW - Superplasticizer KW - Self-compacting concrete 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 - 79 EP - 88 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Umeche, E. L. A1 - Schmidt, Wolfram A1 - Uzoegbo, H. Ch. ED - Schmidt, Wolfram ED - Priebe, Nsesheye Susan T1 - A survey and analysis of locally available cements in South Africa N2 - South Africa and recently Nigeria are the only net exporter of cement in Africa, yet cements are imported into the country mainly on the basis of price competitiveness. This poses potential for scatter in the properties of the cements in the South African market as pricing seems to be the only determining factor that affects Portland cements imported. A survey of cements of grade 42.5N in the South African cement market was carried out to identify major players in the industry. The identified cements, which included four locally produced and one imported cement were then analysed for both chemical composition and physical properties in line with the Eurocode EN 196. Tests carried out include loss on ignition, chloride content, sulphate content, specific surface (Blaine), standard consistence, initial setting time, final setting time, soundness and flexural and compressive strength at 2, 7 and 28 days. The testing program was initiated as part of on-going Africa-wide cement testing competency program in partnership with BAM and PTB in Germany. The performance of the identified cements from the different local manufacturers and the imported cement were analysed and are presented in this paper. These results reveal some similarities and differences in the properties. Particularly of interest is the marked difference in the 28 days compressive strength of the cements. This paper shows that there is need for further tests across the cement industry as some of the cements failed to meet certain requirement as set by EN 196. The paper also recommends the use of proficiency testing schemes in the cement industry of the country to ensure the cement laboratories are providing results of high quality and at the same time act as a check to make sure these laboratories are not failing to meet standard requirements. T2 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa CY - Dar es Salaam, Tanzania DA - 27.01.2016 KW - Cement KW - Proficiency testing KW - EN 196 KW - Standards KW - South Africa PY - 2016 SN - 978-3-9817502-3-2 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 91 EP - 98 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-36876 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - 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 - 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 - 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 - Schmidt, Wolfram A1 - Weba, Luciana A1 - Silbernagl, Dorothee A1 - Mota Gassó, Berta A1 - Höhne, Patrick A1 - Sturm, Heinz A1 - Pauli, Jutta A1 - Resch-Genger, Ute A1 - Steinborn, Gabriele ED - Khayat, Kamal Henry T1 - Influences of nano effects on the flow phenomena of self-compacting 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 selfcompacting concrete. Meanwhile admixtures have become common practice in concrete technology, but the understanding of these highly complex polymers in the entire concrete system lags far behind their application. Due to its complex time-dependent, multi-phase and multi-scale behaviour, flowable concrete systems are highly complicated and cannot be described comprehensively by simple models. It is therefore extremely challenging to identify the relevant parameters that predominantly control flow phenomena on different size scales, since these may occur on any scale between the nano scale (e.g. superplasticizer adsorption) and macro scale (e.g. grading of the aggregates). The present study discusses fundamental mechanisms at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation, and links these effects to macroscopic flow phenomena. 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 - 8th International RILEM Symposium on Self-Compacting Concrete CY - Washington, D.C., USA DA - 15.05.2016 KW - Adsorption KW - Analytics KW - Hydration KW - Polycarboxylate ether KW - Rheology PY - 2016 SP - 245 EP - 254 AN - OPUS4-36882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Potentials for savings in the production of self-compacting and high strength concrete for precast concrete elements N2 - Over the course of the last decades, concrete construction has significantly changed from mass application towards sophisticated more innovative, future oriented, and performance based materials technology. Today concrete no longer consists of cement, water, and aggregates, but can be enhanced significantly by using supplementary additions and chemical admixtures. Advancements in admixtures eventually facilitated the development of new concrete types such as self-compacting concrete (SCC) and high performance concrete (HPC) by uncoupling the workability from the water-cement ratio (w/c). While for traditional concrete types the major mixture parameter for the workability and strength were the w/c and the grading of the aggregates, for SCC and HPC the performance parameters are more complicated and the performance depends highly on the powder components. This makes the system more sophisticated and in parallel more prone to scatter during the production. The complexity and difficulty to predict the effects of changes in the process and mixture makes it very difficult to identify the right potentials for savings. T2 - ICCX Central Europe CY - Ossa, Poland DA - 11.02.2016 KW - Rheology KW - Self-compacting concrete KW - High strength concrete KW - Packing density KW - Superplasticizers PY - 2016 SP - 18 EP - 20 AN - OPUS4-36883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Sonebi, M. A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Rheology modifying admixtures: The key to innovation in concrete technology - a general overview and implications for Africa N2 - Innovative admixture technology has significantly widened up the ränge of possibilities of concrete engineers. For many decades the water to cement ratio (w/c) was the major influencing factor for the performance of concrete. Due to the need to adjust a consistency, which still allowed reasonable workability, the w/c was typically significantly higher than technologically reasonable. Rheology modifying admixtures Support adjusting the concrete consistency largely independent of the w/c. It was only after the invention of the first superplasticizers that modern concrete technology significantly evolved in terms of flowability, strength, and durability, and only due to the steady evolution of the technology modern innovations, such as Self-Compacting Concrete, Ultra-High-Performance Concrete, or Engineered Cementitious Composites were made possible. Today’s superplasticizers are extremely versatile and can be adjusted to individual technologicalspecifications. However, the other side of the coin of versatility is that cementitious Systems incorporating superplasticizers have become more sensitive against environmental influences, such as the environmental temperature, which may cause unwanted effects or demand for supplementary admixture use such as stabilizing admixtures. Hence, concrete mixture composition with admixtures demands for a high level of expertise and offen there is lack of awareness about the mode of Operation of rheology modifying admixtures among concrete technologists. The paper gives a comprehensive overview about rheology modifying admixtures such as superplasticizers or stabilizing agents, and how they can be used depending upon the application in the most favourable way. Based on experiences with the sub-Saharan African concreting boundary conditions, which exhibit many challenges in terms of environmental boundary conditions and construction site logistics, conclusions are finally drawn, how admixtures can be used in the most beneficial way to improve the concrete casting Situation. KW - Rheology KW - Admixtures KW - Concrete KW - Superplasticizers KW - Polycarboxylate ether KW - Viscosity modifying agents PY - 2013 SN - 2224-3224 SN - 2225-0956 VL - 5 SP - 115 EP - 120 PB - International Institute for Conservation of Historic and Artistic Works CY - New York, NY, USA AN - OPUS4-30948 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit A1 - Brouwers, H.J.H. ED - Aguiar, J. B. ED - Jalali, S. ED - Camoes, A. ED - Ferreira, R.M. T1 - Influence of ambient temperature conditions on the effect of stabilising polymers in cementitious building materials T2 - 13th International Congress on polymers in concrete - ICPIC 2010 CY - Funchal-Madeira, Portugal DA - 2010-02-11 KW - Stabilising agent KW - Polycarboxylate ether KW - Polysaccharides KW - Starch ether KW - Biopolymers KW - Rheology KW - Setting PY - 2010 SN - 978-972-99179-4-3 SP - 241 EP - 248 CY - Funchal-Madeira, Portugal AN - OPUS4-21971 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - 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 - Marinescu, M.V.A. A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Uzoegbo, H.C. A1 - Stipanovic Oslakovic, I. A1 - Kumaran, G.S. A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Rogge, Andreas T1 - Recent developments and perspectives regarding the standardisation and quality surveillance of cement in the east, central and south african region N2 - The cement and concrete market in East, Central and Southern Africa is highly fragmented. The concrete industry in this area consists of multiple parties, including producers and suppliers of construction materials, formal and informal contractors, engineers and architects, unions of trades persons and workmen, governmental bodies and formal institutions of research and education. All these institutions mostly do not interact adequately, which makes building with cementitious materials susceptible to damage and failures. Completely opposed to the situation in Europe or North America, cement in Africa is often unaffordable, while manpower is cheap, which results in a questionable economisation of cement. Typically, there is not sufficient awareness of methods to sensibly reducing the cement content in concrete or replace Ordinary Portland Cement by adequate alternative materials. Research activities in this field of technology are often missing completely. Only few countries in the area, such as South Africa, are exempted from these issues. This paper presents the SPIN project, which is a joint project of a consortium of 8 African and 3 European partners within the ACP Science and Technology Programme. The project is funded by the EC and ACP Secretariat is the project body. The main objective of the current project is to strengthen the cement and concrete industry in the East and Central African regions. The project shall generate reasonable solution strategies to implement clean, safe and sustainable cement and concrete technology on the African continent, including general and specific guidelines for sensible application. Furthermore it shall be the kick-off for future projects, research activities and the world-wide expansion of a European-African network. The paper addresses special problems the cement and concrete market in Eastern, Central and Southern African countries has to face. Several options are presented in detail, which shall help overcoming the current situation. Customized solutions for the African market include rational methods for reducing the amount of cement used and the replacement of Ordinary Portland Cement with cheaper alternatives. The use of recycled concrete through a new and economically effective method, as well as the opportunity of using locally available resources is also discussed. T2 - 13th International congress on the chemistry of cement CY - Madrid, Spain DA - 03.07.2011 KW - Africa KW - Clean and safe cement production KW - Scientific network PY - 2011 SN - 978-84-7292-400-0 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 1 EP - 6 AN - OPUS4-24041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Vasilic, Ksenija A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Meng, Birgit ED - Stark, J. T1 - Experimental and numerical studies on calibration of a rotational rheometer for cementitious materials T2 - 17. Ibausil - Internationale Baustofftagung CY - Weimar, Germany DA - 2009-09-23 PY - 2009 SN - 978-3-00-027265-3 VL - 1 SP - 1-1135 - 1-1140 CY - Weimar AN - OPUS4-20300 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan T1 - SCC: a solution to the challenges of concrete construction in Africa PY - 2014 SN - 1560-2710 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 16 EP - 20 PB - Hypenica AN - OPUS4-32301 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Priebe, Nsesheye Susan ED - Schmidt, Wolfram T1 - Parameters controlling superplasticizer cement interactions during the casting and hardening of cement based systems N2 - Concrete of today has only little in common with the traditional concrete used a few decades ago. It has become a high performance material, which can be adjusted for high performance applications and according to ultimate user specifications. The reason for the rapid evolvement was the increasing awareness about how the rheology of concrete can be improved without negatively affecting the mechanical properties of concrete by chemical admixtures. T2 - KEYS 2015 - 1st Symposium Knowledge Exchange for Young Scientists CY - Dar es Salaam, Tanzania DA - 09.06.2015 KW - Superplasticizers KW - Rheology KW - Cement hydration KW - Setting PY - 2015 SN - 978-3-9817149-3-7 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 31 EP - 35 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-33578 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Mode of action of different superplasticisers N2 - Over the course of the last decades, concrete construction has significantly changed from mass application towards sophisticated more innovative, future oriented, and performance based materials technology. Today concrete no longer consists of cement, water, and aggregates, but can be enhanced significantly by using supplementary additions and chemical admixtures. At the same time the concrete specifications are no longer limited to Young’s modulus and compressive strength, but concrete may need to be designed for a multiple of application criteria such as durability, workability, optics, fire behaviour, and many more. However at the same time, the composition of concrete has become more complex due to the higher number of mutually interacting mixture constituents. Understanding the effects of changed mixture constituents is challenging but a good understanding is the key to innovative concrete technology. PY - 2015 SN - 1437-9023 IS - 3 SP - 2 EP - 6 PB - ad-media-Verl. CY - Köln AN - OPUS4-33581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Amziane, Sofiane ED - Sonebi, M. ED - Charlet, K. T1 - Mode of operation of polysaccharide stabilising agent in cement based systems and interactions with superplasticisers N2 - Polysaccharides are incorporated into cement based systems in order to modify the rheological properties. Typically cellulose ethers, sphingan gums or starch ethers are applied. Depending upon their chemistry, molecular architecture, and adsorption tendency, polysaccharides interact differently with the entire cementitious system. Some stabilising agents like diutan gum mainly affect the cementitious paste; other stabilising agents like starch tend to interact with the sand fraction and even with the coarse aggregates. Cellulose shows more divers performances. Often stabilising admixtures like polysaccharides are used, when sophisticated rheological properties are adjusted. Therefore, polysaccharides are often used in combination with superplasticisers. This can cause interactions, particularly when the stabilising agent shows a strong tendency to adsorb on particle surfaces. Adsorptive stabilising agents may reduce the amount of adsorbed superplasticisers, thus affecting both viscosity and yield stress, while non-adsorptive stabilising agents mainly affect the plastic viscosity independently of the superplasticiser. Due to the strong influence of superplasticisers on the yield stress, influences of the stabilising agent on the yield stress retreat into the background, so that their major effect is an increase of the viscosity. The paper provides a comprehensive overview of how different polysaccharide superplasticisers affect cementitious flowable systems and points out the challenges of the combined use of polysaccharides and superplasticisers. Based on rheometric experiments and Observations of the hydration process, time dependent effects on the workability as well as of the hydration of cement are presented. T2 - ICBBM 2015 - 1st International conference on bio-based building materials CY - Clermont-Ferrand, France DA - 22.06.2015 KW - Corrosion potential KW - Chloride migration KW - Electrical resistivity KW - Water absorption KW - Freeze-thaw PY - 2015 SN - 978-2-35158-154-4 N1 - Serientitel: Rilem proceedings – Series title: Rilem proceedings IS - PRO 99 SP - 100 EP - 106 AN - OPUS4-33582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan A1 - Pirskawetz, Stephan A1 - Kühne, Hans-Carsten ED - Amziane, Sofiane ED - Sonebi, M. ED - Charlet, K. T1 - Efficiency of high performance concrete types incorporating bio-materials like rice husk ashes, cassava starch, lignosulfonate, and sisal fibres N2 - Over the last decades concrete has evolved from a simple mass construction material towards a sophisticated multi-component system. The design parameters for the mixture composition of concrete have significantly increased from strength based towards overall or specific performance based. As a result the variety of concrete has increased yielding a number of special concrete technologies such as Self-Compacting Concrete (SCC), High-Performance Concrete (HPC), Strain Hardening Cement Based Composites (SHCC), and many others. Due to their complex mixture compositions and a multitude of possible interactions between constituents, these concrete types are preferably composed of special components like well-defined powders and sophisticated chemical admixtures. This makes such concrete technology expensive and limits their application to regions with the required material supply chains. The paper puts focus on materials, which are less well studied in conjunction with high performance concrete, but which are available in many developing countries, and in particular sub-Saharan Africa. The paper shows how sec can be designed without polycarboxylate ether superplasticizer and well defined fillers, but with lignosulphonate, cassava starch and rice husk ash. The positive effect of well processed rice husk ashes is demonstrated. Furthermore results are presented of SHCC where typical components like polyvinyl alcohol fibres and fluy ash are replaced by sisal fibres and limestone filler, respectively. The results point out that high performance concrete applications do not have to be limited to a boundary framework with availability of well-defined raw material supply structures and sophisticated admixtures or fibres. Concepts are presented how innovative concrete technologies can be developed based on indigenous materials. T2 - ICBBM 2015 - 1st International conference on bio-based building materials CY - Clermont-Ferrand, France DA - 22.06.2015 KW - Corrosion potential KW - Chloride migration KW - Electrical resistivity KW - Water absorption KW - Freeze-thaw PY - 2015 SN - 978-2-35158-154-4 N1 - Serientitel: Rilem proceedings – Series title: Rilem proceedings N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. IS - PRO 99 SP - 208 EP - 214 AN - OPUS4-33583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Controlling the mix - Rheology is critical to optimising cement-based compositions N2 - Since the 1980s the range of additives available to modify the behaviour and performance of concrete has greatly expanded. For many applications, control of concrete rheology is critical to obtaining the best performance. The impact of different concrete admixtures on rheology and other factors affecting their selection are discussed. PY - 2015 SN - 0930-3847 IS - 5 SP - 24 EP - 28 PB - Vincentz CY - Hannover AN - OPUS4-33679 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Paul, S. C. A1 - Ebell, Gino A1 - Van Zijl, G. P. A. G. A1 - Schmidt, Wolfram ED - Schlangen, E. ED - Sierra Beltran, M.G. ED - Lukovic, M. ED - Ye, G. T1 - Cracked and uncracked SHCC specimens under different exposure conditions N2 - This paper describes the fibre-reinforced strain hardening cement-based composite (SHCC) performance under various exposure conditions. Cracked and uncracked SHCC beam specimens were subjected to cyclic wetting and drying under chloride exposure to observe the time of depassivation and corrosion potential of the imbedded reinforcement. Two reference mortars, one of the same strength class as the SHCC (Mortar 1) and the other of high strength class (Mortar 2) were used under the same conditions. Finally, tests for determining the rapid chloride migration coefficient, electrical resistivity, capillary water absorption and freezethaw were also performed to observe the corrosion probability and diffusion rate in uncracked SHCC and mortars. T2 - SHCC3 - 3rd International RILEM conference on strain hardening cementitious composites CY - Dordrecht, The Netherlands DA - 03.11.2014 KW - Depassivation KW - SHCC corrosion crack KW - Lochkorrosion KW - Betonstahl PY - 2014 SN - 978-2-35158-150-6 SN - 978-2-35158-151-3 SP - 25 EP - 32 AN - OPUS4-32462 LA - eng 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 - GEN A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram A1 - Priebe, Nsesheye Susan T1 - SPIN - Spearhead Network for Innovative, Clean and Safe Cement and Concrete Technologies N2 - Globally, cement and concrete experts are at the cutting-edge to sustainable, green, healthy but nonetheless high-performance concrete. Today concrete is not yet well established in Africa, which offers the unique opportunity to build up a cement and concrete market based on the highest available state of technology. As this industry needs high level expertise, a central issue in implementation of skilled technology is crosslinking research institutions and laboratories. It should not be neglected that concrete is a product with low transport ranges. This means that an improved concrete market mainly supports the local economy without exceeding financial drains to the international market. Thus it fosters the fight against poverty, which is an urgent need in most African countries. The project aims to cross-link experts with industry and policy making bodies, aiming to establish sustainable cement and concrete construction in Africa. KW - High-performance concrete KW - Cement technologies KW - Concrete technologies KW - Sustainable development PY - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-387428 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. SP - 1 EP - 3 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-38742 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vasilic, Ksenija A1 - Kühne, Hans-Carsten A1 - Schmidt, Wolfram A1 - Roussel, N. T1 - Numerical simulations of scc casting: parameter determination N2 - The paper addresses numerical modelling of fresh self-compacting concrete. In the previous studies, a numerical tool for casting prediction is built based on the assumption that fresh concrete behaves as a yield-stress fluid and treating zones with rebars as porous media. The present contribution discusses the determination of material parameters, which are required as an input for numerical simulations of casting processes. T2 - International RILEM Conference on Materials, Systems and Structures in Civil Engineering 2016, Segment on Fresh Concrete CY - Lyngby, Denmark DA - 22.08.2016 KW - Fresh concrete KW - Simulation KW - CFD KW - Rheology PY - 2016 SN - 978-2-35158-184-1 SP - 163 EP - 172 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-37446 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Vasilic, Ksenija A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Roussel, N. T1 - Model of SCC flow through reinforced sections: experimental validation N2 - This study focuses on concrete flow in presence of obstacles and develops a mathematical model and a computational approach for SCC flow through reinforced formworks. In order to decrease high computational times needed to simulate castings through reinforced elements, an innovative approach to model the reinforced sections as porous media is proposed here. In the previous work, this numerical model is proved able to simulate the free-surface flow of non-Newtonian fluids through the reinforcement networks. In the present study, the applicability of the model on the concrete flow will finally be proved. The large-scale form-filling experiments with SCC will be conducted and the experiments will be simulated using the proposed numerical model. The numerical model will then be validated through the comparison of the experimental results and the results of the numerical simulations. T2 - 7th RILEM International Conference on Self-Compacting Concrete and 1st RILEM International Conference on Rheology and Processing of Construction Materials CY - Paris, France DA - 02.09.2013 KW - Porous medium KW - Rheology KW - Numerical modelling KW - Reinforcement PY - 2013 SN - 978-2-35158-137-7 SN - 978-2-35158-138-4 SP - 229 EP - 236 PB - RILEM Publishing S.A.R.L CY - Paris, France AN - OPUS4-37442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - Study of the superplasticizer-cement hydration interaction by optical spectroscopy N2 - Nowadays, superplasticizers (SPs) are widely used to increase fluidity and reduce water content in concrete; thus, allowing better workability for final applications. The present study will focus on the hydration effect using comb shape polycarboxylates (PCEs), which are known to allow a very low water/cement ratio (w/c of 0.20) or less.Optical methods have been successfully used for the analysis and monitoring of the interactions between a broad variety of nanoscale and molecular systems like nanoparticles of various chemical composition and different types of organic ligands or biomolecules.This encouraged us to assess the potential of these methods, and particularly fluorescence, for the investigation of the interactions that occur at the interface between hydrate surfaces of cement particles and PCE at a very early stage of concrete formation and to differentiate between the impact of PCE’s molecular structures on such interactions. T2 - 2nd International Conference on the Chemistry of Construction Materials CY - Munich, Germany DA - 10.10.2016 KW - Cement KW - Dye KW - Superplasticizers KW - Fluorescence PY - 2016 SN - 978-3-936028-96-6 VL - 50 SP - 260 EP - 263 PB - Gesellschaft Deutscher Chemiker e.V. CY - Frankfurth am Main AN - OPUS4-38881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mota Gassó, Berta A1 - Schmidt, Wolfram A1 - Pauli, Jutta A1 - Sturm, Heinz T1 - Influences of hydration effects on the flow phenomena of concrete with admixtures N2 - Today, chemical admixtures like superplasticisers and stabilising agents are extremely important for modern concrete technology. These agents have meanwhile become common practice in concrete technology, but the understanding within the entire system lags far behind their application. The macroscopic rheology of concrete in the presence of superplasticizers strongly depends upon effects on a much smaller scale such as the hydration of the cement, the adsorption of superplasticizers, and the pore solution chemistry. T2 - 2nd International Conference on the Chemistry of Construction Materials CY - München, Germany DA - 10.10.2016 KW - Rheology KW - Cement KW - Superplasticiser PY - 2016 SN - 978-3-936028-96-6 VL - 50 SP - 276 EP - 279 PB - Gesellschaft Deutscher Chemiker e.V. CY - Frankfurt am Main AN - OPUS4-38849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - 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 - TY - CONF A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, Ines A1 - Breitschaft, G. A1 - Virchow, S. ED - Diouri, A. ED - Boukhari, A. ED - Ait Brahim, L. ED - Bahi, L. ED - Khachani, N. ED - Saadi, M. ED - Aride, J. ED - Nounah, A. T1 - Challenges of the growing African cement market – environmental issues, regulative framework, and quality infrastructure requirements N2 - The African cement, concrete and construction business is growing at rapid pace. The cement sales are expected to grow rapidly until 2050. The number of newly built cement plants increases dramatically and in addition more cements are being imported from outside the continent, e.g. from Turkey, Pakistan, Indonesia, and China, driven by overcapacities in the countries of origin. This causes a high number of potentials and challenges at the same time. Newly built cement plants can operate directly at best technological state of the art and thus incorporate more sustainable technologies as well as produce new and more sustainable products such as cements blended with sustainable supplementary cementitious materials such as calcined clays, and industrial or agricultural by products. At the same time the new variety of binding agent as well as the international imports, which are driven by price considerations, make the cement market prone to quality scatter. This puts pressure on the quality control regulations and institutions to ensure safety of construction, healthy application, and environmental safety for the population. The paper presents possible solutions to build up the rapidly increasing African cement production more sustainably than in the rest of the world as well as the related challenges and obstacles that need to be overcome. Based on experiences with a series of pan-African cement testing laboratory proficiency schemes conclusions are made on technical, regulative and political level. T2 - 2nd International Congress on Materials & Structural Stability (CMSS-2017) CY - Rabat, Morocco DA - 22.11.2017 KW - Quality Infrastructure KW - Africa KW - Proficiency Testing KW - Cement KW - Admixtures PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-444330 SN - 2261-236X VL - 149 SP - 01014-1 EP - 01014-8 PB - EDP Sciences CY - Les Ulis AN - OPUS4-44433 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 - 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 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of rheology modifying admixtures on early hydration of cementitious suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has enormous influence on the early hydration of cement. C3A as the most reactive phase of Portland cement plays a significant role in early hydration reactions and affects the rheological performance. Therefore, this paper presents experimental results about the influence of delayed addition of PCEs on the Hydration of cement and C3A-gypsum pastes investigated by isothermal heat flow calorimetry. Complementary in-situ XRD was carried out on C3A pastes to analyze hydration and phase changes related to the addition of PCE. Cement pastes with a delayed addition of PCE showed less Retardation compared to simultaneous addition. The alteration caused by PCE is much more pronounced for C3A-gypsum mixes. With a delayed addition of SP, the hydration of C3A is less retarded or even accelerated. It is obvious that there is less retardation the later the addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and hydration rates. XRD results showed that more C3A is dissolved in the presence of PCE. Also, the gypsum depletion occurs earlier in the presence of PCE and even faster with delayed addition. Without PCE AFm starts to form just after the gypsum depletion. However, in the presence of PCE AFm already starts to form at the beginning of the hydration. Due to the faster gypsum depletion in the presence of PCE, also the transformation from ettringite into AFm begins earlier, but takes longer as without SP. T2 - 15th International Congress on the Chemistry of Cement CY - Prague, Czech Republic DA - 16.09.2019 KW - Cement KW - C3A KW - Early hydration KW - Polycarboxylate ether (PCE) KW - Delayed addition PY - 2019 SP - 1 EP - 8 AN - OPUS4-49104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram T1 - Peculiarities of African cement and concrete markets: challenges and opportunities N2 - Today's African concrete construction environment differs greatly from that in Europe, Japan or North America. Europe can look back on a concrete tradition of more than 150 years. Standardising documents and guidelines have existed for over 100 years, and formed the foundation of modern Standards adopted and applied in many regions of the world. Technological developments in cement production are also strongly influenced by environmental conditions of the Northern hemisphere. In contrast, with the exception of South Africa, most countries of sub-Saharan Africa started cement production in the 1950s to 1960s, followed by a period of political and economic upheaval. As a result, there have not been serious approaches towards customised Solutions for concrete construction for conditions specific to sub-Saharan Africa; in most countries overseas Standards are applied, as a matter of course. PY - 2013 SN - 1560-2710 VL - 16 IS - 4 SP - 1 PB - Hypenica AN - OPUS4-30419 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Schmidt, Wolfram T1 - Design concepts for the robustness improvement of self-compacting concrete - Effects of admixtures and mixture components on the rheology and early hydration at varying temperatures N2 - In Europe a multi-national research project was initiated entitled “Rational Production and Improved Working Environment through Using Self-Compacting Concrete”, followed by another project entitled “Testing SCC”, which helped spreading the benefits of SCC to a wide range of appliers. This project was also the basis of a widely accepted European guideline on Self compacted concrete published by the European industry association bibm, CEMBUREAU, EFCA, EFNARC, ERMCO, which again builds the basis of the European standards for the testing of SCC (EN 12350, Parts 8 to 12) as well as for the actual modernisation of the European concrete standard EN 206-1. PY - 2014 SN - 978-90-386-3598-9 U6 - https://doi.org/10.6100/IR771936 VL - 193 SP - 1 EP - 308 PB - Eindhoven University of Technology CY - Eindhoven, The Netherlands AN - OPUS4-30826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Controlling rheology - The key to individual concrete performance specifications N2 - During the last three decades concrete has emerged from a rather simple mass construction material based on only the three components cement, water, and aggregates towards a high performance material, which can be adjusted for high performance applications and according to ultimate user specifications. The reason for the rapid evolvement was the increasing awareness about how the rheology of concrete can be improved without negatively affecting the mechanical properties of concrete. Hence, mineral additions and in particular Chemical admixtures have been the most influential factors for the technological boost since approximately the 1980s. The incorporation of superplasticizers into concrete mixture compositions eventually facilitated concrete engineers to improve the workability properties without need to increase the water-cement-ratio (w/c) and furthermore to significantly reduce the w/c without loss of workability. This finally resulted in concrete with higher performance and specified properties. Fillers are basically used to improve the particle packing of cementitious Systems, but they can also be used beneficially to support the rheology, since they modify the water demand and may interact with superplasticizers as well. Finally, supplementary admixtures like polysaccharides have become more populär in the field of mortar, plaster, and grout technology. They can have a variety of rheological effects on cementitious Systems, which can be used to individually adjust their performance. The possibility to control the rheology and the significantly widened ränge of consistencies that can be adjusted opened up the gates for modern concrete and any type of high performance concrete. Therefore, without doubt, it can be concluded that the capability to control the rheology of concrete Systems can be considered as the catalyst for the invention of the many recent mortar and concrete innovations such as polymer modified cementitious composites (PCC) self-compacting concrete (SCC), high-performance concrete (HPC), ultra-high performance concrete (UHPC) or engineered cementitious composites (ECC). Therefore, understanding the rheology of cementitious Systems and how to control the workability by the use of Chemical admixtures is the key to innovations in concrete technology. However, the other side of the coin of versatility is that sophisticated cementitious Systems have become more sensitive. Hence, concrete mixture composition with admixtures demands for a high level of expertise and often there is lack of awareness about the mode of Operation of rheology modifying admixtures among concrete technoiogists. The paper gives a comprehensive overview about rheology modifying constituents such as superplasticizers, stabilising agents, and mineral fillers, and how they can be used depending upon the application in the most favourable way. T2 - Facade coatings and plasters - European coatings conference CY - Düsseldorf, Germany DA - 29.10.2013 PY - 2013 SP - 93 EP - 102 PB - Vincentz AN - OPUS4-30827 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Patrick A1 - Gluth, Gregor A1 - Schmidt, Wolfram A1 - Astorg, Adéle A1 - Kühne, Hans-Carsten A1 - Brouwers, H.J.H. T1 - Rheological properties of microsilica and sodium aluminate based one-part geopolymers compared to ordinary Portland cement T2 - 5th International Conference Non-Traditional Cement & Concrete CY - Brno, Czech Republic DA - 2014-06-16 KW - Alkali-activated binders KW - One-part geopolymers KW - Rheology PY - 2014 SN - 978-80-214-4867-4 SP - 71 EP - 74 AN - OPUS4-31159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Becker, S. A1 - Lu, Z. A1 - Leinitz, Sarah A1 - Schmidt, Wolfram A1 - Stephan, D. A1 - von Klitzing, R. ED - Mechtcherine, V. ED - Khayat, K. ED - Secrieru, E. T1 - Particle Interactions in Silica Systems in Presence of Superplasticizer N2 - The flowability of cement paste is of great importance in today’s construction industry and is influenced by additives such as superplasticizers (SP). One type of SPs are polycarboxylate ether type SPs. These additives electrostatically bind with the negatively charged carboxylic groups at the backbone to the positively charged clinker phases. To model positively charged clinker phases with adsorbed SP, silicon Wafers are pre-coated with cationic polyethylenimine (PEI) and SP is adsorbed onto the coated surface (Si/PEI/SP). Two different polycarboxylate ether type (PCE) SP are compared – one for ready-mix concrete and one for precast concrete. In this preliminary study the interaction forces between Si/PEI/SP surface and a silica microsphere (colloidal probe) are investigated under mild physico-chemical conditions (pH *6, ion concentration <10−5 M) using Colloidal Probe Atomic Force Microscopy (CP-AFM). The interaction force between the model surfaces is attractive for low concentration of SP. The force changes from attractive to repulsive by increasing amount of SP. The force upon approach reveals a biexponential behavior. The exponential decay at large and short surface separations are attributed to electrostatic and steric interactions, respectively. The steric forces of the SP for ready-mix concrete show a steeper onset than the SP for precast concrete. The quantification of these interaction forces will be compared to rheological measurements of similar systems. Furthermore, the parameters will be changed to better approach the conditions in real systems, i.e. higher pH and ionic strength. This helps to understand how the forces on the nanoscale influence the macroscopic rheology. KW - Interfacial forces KW - Silica beads KW - Superplasticizer KW - AFM PY - 2019 SN - 978-3-030-22565-0 U6 - https://doi.org/10.1007/978-3-030-22566-7 SN - 2211-0844 VL - 23 SP - 571 EP - 579 PB - Springer ET - 1 AN - OPUS4-49183 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Lu, Z. A1 - Becker, S. A1 - Leinitz, Sarah A1 - von Klitzing, R. A1 - Schmidt, Wolfram A1 - Stephan, D. ED - Mechtcherine, V. ED - Khayat, K. ED - Secrieru, E. T1 - Rheological properties of silica beads in the presence of different polymers and electrolyte N2 - Properties of interstitial liquid phase in cement paste, including the species and concentrations of polymers and ion etc., play an important role for the rheological properties of cementitious materials. In order to better understand their effect, an inert model substance, spherical silica beads (SBs) with defined surface and granulometry were used in the presence of electrolytes (CaCl2) and/or different polymers, including polycarboxylate superplasticizer (PCE) and polyethylene glycol (PEG). It was found the presence of Ca2+ greatly increases the viscosity and yield stress of silica beads paste (SBP), which is proportional to the [Ca2+]. For the effect of PCE, the addition of PCE is beneficial to the flowability of SBP, but a high dosage of PCE leads to a reversal effect. Furthermore, the yield stress firstly increases and then decreases with increasing [Ca2+] under the same dosage of PCE. The addition of PEG always increases the yield stress of SBP, regardless of the ion concentration and the presence or not of PCE. KW - Rheological properties KW - Ions KW - Superplasticizer KW - Silica beads PY - 2019 SN - 978-3-030-22565-0 SN - 978-3-030-22566-7 U6 - https://doi.org/10.1007/978-3-030-22566-7_72 SN - 2211-0844 VL - 23 SP - 619 EP - 627 PB - Springer ET - 1 AN - OPUS4-49185 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Leinitz, Sarah A1 - Lu, Z. A1 - Becker, S. A1 - Stephan, D. A1 - von Klitzing, R. A1 - Schmidt, Wolfram ED - Mechtcherine, V. ED - Khayat, K. ED - Secrieru, E. T1 - Influence of different accelerators on the rheology and early hydration of cement paste N2 - Special applications like pumping, spraying or printing of concrete require the precise adjustment of very specific rheological properties at different time steps during the casting process. Superplasticizers such as polycarboxylate ethers (PCE) can be used to obtain the required flowability, which, possibly in combination with additional rheology modifying admixtures, generate the required specified consistency. However, after the application, the concrete should change the rheological properties immediately in order to avoid deformations at rest. Therefore, the use of accelerators can be effective. Accelerators influence the hydration of cementitious materials, and thus the rheological properties over the course of time and the setting. In this paper, the influence of different accelerators on the rheology and early hydration of cement paste as well as the interaction of accelerator and PCE are presented. Methods like rheometry, needle penetration tests and practical Tests like spread flow were applied. The used accelerators showed accelerating behavior on the cement pastes without and in the presence of PCE. At the same time an influence on the rheology could be observed. This effect was less in the mixes with PCE, especially at the highest water/cement ratio (w/c). KW - Rheology KW - Cement paste KW - Accelerator KW - Superplasticizer KW - Setting PY - 2019 SN - 978-3-030-22565-0 U6 - https://doi.org/10.1007/978-3-030-22566-7 SN - 2211-0844 VL - 23 SP - 106 EP - 115 PB - Springer ET - 1 AN - OPUS4-49139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramirez Caro, Alejandra A1 - Pauli, Jutta A1 - Mota, Berta A1 - Crasselt, Claudia A1 - Artemeva, Elena A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - A Spectroscopic Study of the Superplasticizer Effect on Early Cement Hydration N2 - Organic/inorganic mixtures were prepared from ordinary Portland cement (OPC), water (w/c 0.22), a fluorescent dye in aqueous solution (stable at alkaline pH; BAM-I), and two different comb shape polycarboxylates (PCEs), i.e., high charge (PCE-HC) and low charge (PCE-LC), respectively. Rheological and calorimetric measurements were performed prior to optical studies in order to select PCE concentrations. Absorption and fluorescence spectroscopy of the system OPC + BAM-I (CBAM-I) revealed maxima of dye BAM-I located at 645 nm and 663 nm, respectively. In presence of PCE-HC and PCE-LC, these mixtures displayed a small red shift in reflectance and a faster decrease in intensity compared to studies with CBAM-I; however, only slight differences were observed between the different PCEs. With time, all systems exhibited a decrease in intensity of BAM-I in absorption/reflectance and emission. This could be caused by dye adsorption and possibly decomposition when in contact with cement particles or hydration products. T2 - The Sixth International Symposium on Nanotechnology in Construction (NICOM6) CY - Hong Kong, China DA - 02.12.2018 KW - Cement KW - Optical Spectroscopy KW - Dye KW - Hydration PY - 2018 SP - 1 EP - 9 AN - OPUS4-49378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-484848 UR - http://isee-africa.com/wp-content/uploads/2019/07/Innovation-Science-Engineering-Education_High-Quality.pdf SN - 978-3-9818564-2-2 SP - 189 EP - 193 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-48484 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - 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 - CONF A1 - Schmidt, Wolfram A1 - Radebe, N. ED - Schmidt, Wolfram T1 - Biased by analytical equipment N2 - Today, in scientific events often a certain separation between researchers from laboratories with highly sophisticated equipment and those from less privileged laboratories can be observed. It is not an uncommon situation that results presented at conferences are rubbished or ridiculed because the investigator only used low-end analytical methods. The assessment of the study is then biased based on the equipment, regardless of the actual quality of the study. T2 - ISEE Africa - Innovation, Science, Engineering, Education CY - Nairobi, Kenya DA - 30.01.2019 KW - Analytics KW - Africa KW - Bias KW - Science KW - Research PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-484877 UR - http://isee-africa.com/wp-content/uploads/2019/07/Innovation-Science-Engineering-Education_High-Quality.pdf SN - 978-3-9818564-2-2 SP - 203 EP - 204 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-48487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram 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 U6 - http://nbn-resolving.de/urn/resolver.pl?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 - Schmidt, Wolfram T1 - Potentials for sustainable cement and concrete technologies - Comparison between Africa and Europe N2 - Cement and concrete technologies in Africa provide vast potentials for sustainable future technologies as well as enormous challenges. The main focus of the symposium is to address existing challenges, possible solutions, and future potentials with all participants. This symposium also aims at offering a platform for networking with relevant players in science and industry. T2 - Cement and Concrete Related Issues for the African Market CY - Yaoundé, Cameroon DA - 02.11.2017 KW - Cement KW - Admixtures KW - Rheology KW - Sustainability KW - Environment PY - 2017 AN - OPUS4-43541 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Concrete casting robustness improvement due to active rheology control 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 CY - Rabat, Morocco DA - 21.11.2017 KW - Rheology KW - Control charts KW - Cusum KW - Additive manufacturing KW - Online quality control PY - 2017 AN - OPUS4-43542 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, Ines Leana A1 - Breitschaft, Gerhard A1 - Virchow, Stephen T1 - Challenges of the growing African cement market – Environmental issues, regulative framework and quality infrastructure requirements N2 - The African cement, concrete and construction business are growing at rapid pace. The cement sales are expected to grow tremendously until 2050. The number of newly built cement plants increases dramatically and in addition more cements are being imported from outside the continent, e.g. from Turkey, Pakistan, Indonesia, and China, driven by overcapacities in the countries of origin. This causes a high number of potentials and challenges at the same time. New cement plants can operate directly at best technological state of the art and thus incorporate more sustainable technologies as well as produce new and more sustainable products such as cements blended with sustainable supplementary cementitious materials such as calcined clays, and industrial or agricultural by products. At the same time the new variety of binding agent as well as the international imports, which are driven by price considerations, make the cement market prone to quality scatter. This puts pressure on the quality control regulations and institutions to ensure safety of construction, healthy application, and environmental safety for the population. The paper presents possible solutions to build up the rapidly increasing African cement production more sustainably than in the rest of the world as well as the related challenges and obstacles that need to be overcome. Based on experiences with a series of pan-African cement testing laboratory proficiency schemes conclusions are made on technical, regulative and political level. T2 - 2nd International Congress on Materials & Structural Stability CY - Rabat, Morocco DA - 21.11.2017 KW - Quality infrastructure KW - Round Robin KW - Proficiency testing KW - Cement KW - Africa PY - 2017 AN - OPUS4-43543 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Bio-adhesives and bio-chemicals from bio-mass N2 - After a brief introduction into past and modern concrete, the relevance of sustainable concrete technologies is emphasised from a global perspective. In order to minimise the environmental impact of cement and concrete in the world, solutions for alternative binder materials as well as rheology and performance modifying additives are presented based on local bio-based resources. However, the perception of bio-based constituents is typically rather negative in construction materials and its application is often limited to low-end construction. In order to show that this is not inevitable, the lecture ends with a number of case studies for the use of bio-based materials for high performance concrete applications. T2 - Sustainable Adhesives from Bio-Mass (SAB) Symposium CY - Greensboro, North Carolina, USA DA - 26.01.2017 KW - Starch KW - Bio-based materials KW - Superplasticizer KW - Ash KW - Concrete KW - Cement PY - 2017 AN - OPUS4-43544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Agricultureal Waste for High Performance Construction - Potentials for Innovation, Markets, and Sustainability N2 - The presentation provides an overview of potentials for high performance construction materials based on local agricultural waste materials in different regions in Africa. T2 - 5th German-African Infrastructure Forum 2017 CY - Düsseldorf, Germany DA - 08.11.2017 KW - Cement KW - Concrete KW - Bio-based materials KW - Sustainability KW - Africa PY - 2017 AN - OPUS4-43545 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, Ines Leana ED - Schmidt, Wolfram ED - Tchetgnia Ngassam, Ines Leana T1 - Cement proficiency testing scheme 2016/2017 - Final report N2 - The cement proficiency testing (PT) scheme was set up by the German Metrology Institute (PTB) and the Federal Institute for Materials Research and Testing (BAM) in 2012. The PT scheme was a spin-off from a European Commission and African, Caribbean and Pacific-Group of States funded project entitled SPIN – Spearhead Network for Innovative, Clean and Safe Cement and Concrete Technologies (www.spin.bam.de). The SPIN project aimed at crosslinking experts in industry and policy making bodies, with the prospect of establishing a sustainable cement and concrete construction capacity in Africa. After a successful first pan-African proficiency testing scheme in 2012/2013, it was decided to establish the scheme permanently and independent of the SPIN project. The main focus of setting up a testing scheme was to enable all cement testing laboratories in Africa to evaluate their competence and efficiency in cement testing and further enhance their capacity to obtain better quality products according to their environment. The acronym developed for the PT scheme is PACE-PTS (Pan-African Cement Proficiency Testing Scheme). The framework for the PT scheme was set up jointly among the organisers and the first participants. The first PT scheme was initiated in Dar Es Salaam in 2012 followed by a final workshop in Berlin in 2013. The second PT scheme began in 2014. A final workshop was organised in Dar es Salaam in 2015. The third and current scheme was started in 2016 and the final workshop is held in Yaoundé. KW - PACE-PTS KW - Round Robin KW - Proficiency testing KW - Cement KW - Quality infrastructure PY - 2017 VL - 3 SP - 1 EP - 74 PB - BAM CY - Berlin AN - OPUS4-43546 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Govin, Alexandre A1 - Schmidt, Wolfram A1 - Bartholin, M. C. A1 - Grosseau, P. ED - Amziane, Sofiane ED - Sonebi, Mohammed ED - Charlet, Karine T1 - Effect of Guar gum derivatives combined with superplasticizers on properties of Portland cement pastes N2 - Chemical admixtures allow to create a variety of fresh and hardened state properties in cementitious materials. In the case of self-compacting concrete, plasticizers or superplasticizers are introduced with the aim to decrease the yield stress and the viscosity of the materials. However, in order to prevent segregation and bleeding, and to improve the water retention of cement-based system, stabilizing agents or viscosity agents are often introduced in addition. Among these admixtures, polysaccharides are most commonly used. The aim of this study is to provide an understanding of competitive or synergetic effects induced by the combination of hydroxypropyl guar stabilizing agents (HPG) and superplasticizers on cement pastes. Two polycarboxylate superplasticizers (PCE) exhibiting different charge densities and one HPG were studied. It was found that the combination of HPG with PCE superplasticizer strongly affects the rheological behavior of cement pastes. Despite the presence of HPG, the viscosity of the pastes strongly decreased with increasing dosage of PCE until it became close to the viscosity of a cement paste with PCE only. However, the use of HPG in combination with PCE allows maintaining a significant yield stress in the cement paste compared to PCE alone. The increase in the charge density of the PCE seemed to amplify the drop of the viscosity and to reduce the gain on the yield stress induced by HPG. The results also highlight a delay in the setting-time of the cement paste by adding HPG and PCE. The delay induced by HPG is significantly lower than that generated by PCEs. However, the combination of the both kind of admixtures leads to a slightly shorter setting-time compared to the PCE alone. T2 - Second International RILEM Conference on Bio-based Building Materials, 21-23 June 2017 CY - Clermont-Ferrand, France DA - 21.06.2017 KW - Rheology KW - Cement KW - Guar Gum KW - Polysaccharide KW - Superplasticizer PY - 2017 SN - 978-2-35158-192-6 SP - 55 EP - 61 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-43547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - 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 - 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 - 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 - CHAP A1 - Schmidt, Wolfram A1 - Leinitz, Sarah A1 - Mota, Berta A1 - Crasselt, Claudia ED - Liu, Jiaping ED - Wang, Ziming ED - Holland, Terence ED - Huang, Jing ED - Plank, Johann T1 - Influence of the aqueous phase of cement paste on the rheology in the presence of PCE N2 - The paper presents rheometric results and hydration curves for cementitious systems based on cement mixed with different aqueous phases at solid volume fraction of  = 0.45. The varied aqueous phases were deionized water, limewater, the filter residue of a cement paste mixed at w/c = 2.0, and the filtrate of cement paste at solid volume fraction of 0.45. Each cementitious system provided different amounts and sizes of particles formed in the aqueous phase. The pastes were observed with and without polycarboxylate ether based superplasticizer. It was observed that the presence of particles causes higher PCE saturation dosages to achieve a minimum value, but the minimum value is only affected in the case of large particles. In all cases with and without PCE, the presence of small particles causes increased plastic viscosity. In addition, with decreased number and size of hydrates in the aqueous phase the hydration was retarded, which was specifically pronounced in the presence of PCE KW - Aqueous phase of cement paste KW - Polycarboxylate ether KW - Rheology KW - Yield stress KW - Plastic viscosity KW - Heat of hydration KW - Syngenite KW - Solid volume fraction PY - 2018 SN - 978-1-64195-029-9 SP - SP-329-34, 428 EP - 443 PB - American Concrete Institute CY - Farmington Hill, Michigan AN - OPUS4-47107 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of Rheology Modifying Admixtures on Hydration of Cementitious Suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed addition time of PCE SPs on hydration of cement and alite pastes, investigated by isothermal heat flow calorimetry. For cement as well as for alite pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. The retardation caused by PCE is much more pronounced for alite than for cement mixes. If PCE is added later to the mix, the induction period is shortened and the hydration is accelerated compared to simultaneous addition. This applies for cement and alite pastes. With delayed PCE addition the alite shows a clearly less retarded setting and main hydration than after simultaneous addition. It is obvious that for alite pastes there is less retardation the later the addition of SP. T2 - 6th International Symposium on Nanotechnology in Construction CY - Hong Kong, China DA - 02.12.2018 KW - Polycarboxylate ether (PCE) KW - Early hydration KW - Cement PY - 2018 SP - 1 EP - 8 AN - OPUS4-47204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Govin, A. A1 - Schmidt, Wolfram A1 - Bartholin, M. C. A1 - Grosseau, P. ED - Amziane, Sofiane ED - Sonebi, M. T1 - Effect of Guar Gum Derivatives Combined with Superplasticizers on Properties of Portland Cement-Pastes N2 - Chemical admixtures allow to the create a variety of fresh and hardened state properties in cementitious materials. In the case of self-compacting concrete, plasticizers or superplasticizers are introduced with the aim to decrease the yield stress and the viscosity of the materials. However, in order to prevent segregation and bleeding, and to improve the water retention of cement-based system, stabilizing agents or viscosity agents are often introduced in addition. Among these admixtures, polysaccharides are most commonly used. The aim of this study is to provide an understanding of competitive or synergetic effects induced by the combination of hydroxypropyl guar stabilizing agents (HPG) and superplasticizers on cement pastes. Two polycarboxylate superplasticizers (PCE) exhibiting different charge densities and one HPG were studied. It was found that the combination of HPG with PCE superplasticizer strongly affects the rheological behavior of cement pastes. Despite the presence of HPG, the viscosity of the pastes strongly decreased with increasing dosage of PCE until it became close to the viscosity of a cement paste with PCE only. However, the use of HPG in combination with PCE allows maintaining a significant yield stress in the cement paste compared to PCE alone. The increase in the charge density of the PCE seemed to amplify the drop of the viscosity and to reduce the gain on the yield stress induced by HPG. The results also highlight a delay in the setting-time of the cement paste by adding HPG and PCE. The delay induced by HPG is significantly lower than that generated by PCEs. However, the combination of the both kind of admixtures leads to a slightly shorter setting-time compared to the PCE alone. T2 - 2nd International Conference on Bio-based Building Materials & 1st Conference on ECOlogical valorisation of GRAnular and FIbrous materials CY - Clermont-Ferrand, France DA - 21.06.2017 KW - Guar gum KW - Polysaccharides KW - Superplasticizer KW - Cement KW - Rheology PY - 2017 VL - PRO 119 SP - 55 EP - 61 PB - RILEM Publications S.A.R.L. CY - Paris AN - OPUS4-41038 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Shamsuddoha, Md A1 - Hüsken, Götz A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Baeßler, Matthias ED - Alexander, M.G. ED - Beushausen, H. ED - Dehn, F. ED - Moyo, P. T1 - Workability and mechanical properties of ultrafine cement based grout for structural rehabilitation: A parametric study on the partial replacement with SCMs N2 - Grouting is a universal repair and strengthening technique, which is constantly used for structural remediation of concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. Having an extremely small particle size of only few microns, ultrafine cements are ideal for grouting applications due to their superior permeability and compressive strength properties of the hardened cement paste compared to that of the less-expensive, but coarser ordinary Portland cements. Supplementary cementitious materials (SCMs) are often used to replace ultrafine cement in order to modify certain properties and to reduce costs. The aim of this experimental study is to investigate the effect of three supplementary materials: microsilica (MS), fly ash (FA), and metakaolin (MK) on the workability, and mechanical properties of an ultrafine cement based grout with a constant water-binder ratio and constant superplasticizer content. Maximum percentages of replacement with ultrafine cement were 6% by volume of cement for MS and 16% for FA, and MK. In general, results suggest that the workability is improved by addition of FA, whereas is reduced, when modified with MS and MK. The compressive strength of grout after cement replacement remains comparable to that of pure cement grout. However, there is a tendency of the MS to positively affect the compressive strength opposite to FA, whereas flexural strength is positively affected by FA. Based on the results, it is evident that grouts with Hägerman cone flow more than 500 mm and compressive strength of more than 90 MPa after 28 days can be produced. T2 - International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2018) CY - Cape Town, South Africa DA - 19.11.2018 KW - Grouting KW - Repair KW - Box-Behnken KW - Supplementary cementitious materials KW - Analysis of variance PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-464769 SN - 2261-236X VL - 199 SP - 07006-1 EP - 07006-7 PB - MATEC Web of Conferences AN - OPUS4-46476 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz ED - M. Tyrer, ED - E. Ganjian, ED - West, A. T1 - Influence of rheology modifying admixtures on hydration of cementitious suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed Addition time of PCE SPs on hydration of cement and tricalcium aluminate (C3A) pastes, investigated by isothermal heat flow calorimetry. For cement pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. With delayed PCE addition the cement shows a less retarded setting than with simultaneous addition. The alteration caused by PCE is much more pronounced for C3A and gypsum mixes than for cement. If the SP is added simultaneous, the exothermic peak of C3A is retarded. However, with delayed addition of SP the hydration is shortened, the gypsum depletion is fastened and the exothermic peak occurs less retarded or even accelerated compared to simultaneous addition. It is obvious that for C3A pastes there is less retardation the later the Addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and hydration rates. The rate of reaction in the second stage is lower, discernible in decreased slopes and broader peaks. Besides this, a distinct ramp in the C3A heat flow curves within the first stage of C3A hydration occurs for all pastes with delayed addition of SP, which suggests an accelerated ettringite formation. T2 - 38th Cement and Concrete Science Conference CY - Coventry, UK DA - 10.09.2018 KW - Cement hydration KW - Polycarboxylate ether KW - C3A hydration PY - 2018 SN - 978-1-84600-088-1 SP - 64 EP - 67 CY - Coventry, UK AN - OPUS4-45995 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Promising bio-based material solutions for more sustainable concrete N2 - Today, concrete engineers can vary consistencies between very stiff and self-compacting. At the same time engineers can opt for a vast variety of binders. The possibility to use optimised mineral binders and to tailor rheological properties of concrete eventually opened up the path to multiple new technologies, where design criteria are no longer limited to the Young’s modulus and the compressive strength, but often comprise additional added value. It can therefore be concluded that the capability to control the rheology and the interactions particles can be considered as the catalyst for concrete innovations such as polymer modified cementitious composites (PCC) self-compacting concrete (SCC), high-performance concrete (HPC), ultra-high performance concrete (UHPC) or strain hardening cement based composites (SHCC). In the same way rheology modifying additions, SCMs and admixtures will become key parameters in mastering the challenges of the next decades such as: - Additive manufacturing/3D-printing - Overcoming pumping height limitations - Casting at extreme temperatures - Tailored rheology at delivery In many regions in the Southern hemisphere the effective use of SCMs, additions and chemical admixtures for concrete could significantly contribute to solve problems induced by the challenging climatic conditions, but particularly in many countries with challenging climatic conditions, it is difficult to use them, due to lacking local supply and supply infrastructure, and often the awareness of the value of local mineral resources is missing. However, the long distance transportation of mineral resources and chemicals is not very environmentally friendly and the economic consequences are dramatic. However, bio-based constituents and chemicals have been used in construction for ages effectively. Due to the enormous relevance of binders, fillers and rheology modifying admixtures it is worthwhile to recollect that nature provides an enormous variety of products that can be used readily or with low processing. Today, the use of petrol based polycarboxylate ether superplasticizers has become quite common in concrete technology due to their versatility, but their uncomplicated and cost efficient availability is limited in many countries in the world. However, alternatives are available, which can be found locally. In addition many agricultural wastes today are dumped, although they could be converted to reactive ashes easily. Plant extracts have been used to modify the properties of concrete for long time. These plants are typically regionally abundantly available, cheap, and they are environmental friendly. They do not require special caring for seedlings, weeding or manuring to grow since they grow wildly. The talk will present an overview of various options for binders, fillers and rheology modifying admixtures, that can be found in nature, and that may become a real alternative, once their interaction within the complex cementitious system is well understood. T2 - Peak Forum on Sustainable Civil Engineering Materials CY - Shanghai, China DA - 18.05.2017 KW - Cement KW - Concrete KW - Sustainability KW - Bio-based materials KW - Polysaccharides KW - Supplementary cementitious materials PY - 2017 AN - OPUS4-41031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Influence of nano scale effects on the macroscopic rheology N2 - Chemical admixtures like superplasticisers or stabilising agents are of ever increasing importance for modern concrete technology. They liberate the workability of concrete from its dependency on water content, and thus, open the gate towards innovative and future oriented concrete technologies. Meanwhile admixtures have become common practice in concrete technology, but the understanding of these highly complex polymers in the entire concrete system lags far behind their application. Due to its complex time-dependent, multi-phase and multi-scale behaviour, flowable concrete systems are highly complicated and cannot be described comprehensively by simple models. It is therefore extremely challenging to identify the relevant parameters that predominantly control flow phenomena on different size scales, since these may occur on any scale between the nano scale (e.g. superplasticizer adsorption) and macro scale (e.g. grading of the aggregates). The present study discusses fundamental mechanisms at the interface between particle or hydrate surfaces and the fluid phase at a very early stage of concrete formation, and links these effects to macroscopic flow phenomena. Based on the observations of the nano scale effects, it seems that higher sensitivity against variations in the constituents, the handling, or the boundary condition are the inevitable price for higher performances. However, eventually a very effective method is introduced that helps to maintain stable processes regardless of the root cause for performance changes based on an efficient in-situ process control scheme and superplasticizer and stabilising agents as counter actions. T2 - International Workshop on Nano-Engineered Meta-materials for Civil Infrastructures CY - Jinan, China DA - 20.5.2017 KW - Rheology KW - Meta materials KW - Nano engineering KW - Admixtures KW - Cement KW - Ettringite PY - 2017 AN - OPUS4-41032 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leinitz, Sarah A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten ED - Priebe, Nsesheye Susan T1 - Influence of stabilising agents on limestone filler and cement pastes N2 - The paper showed that the STA behave completely different in pastes with LSF and cement, respectively, as well as with or without PCE. While STA can affect plastic viscosity and yield stress in LSF and cement pastes, the addition of PCE causes that the STA have mainly an impact on plastic viscosity, except DGUM and ST-low. The performance of STA in LSF and cementitious systems can vary greatly due to different ionic strengths of the liquid phase. The charges due to modification of the starches have an intense influence on the rheological properties in pastes. The combined use of PCE and STA can lead to a significant increase of the plastic viscosity without a strong effect to the yield stress. For the evaluation of the effectivity of STA the ionic strength of the liquid phase and the solid volume fraction of the binder have to be taken into account. Further influences can arise from grain size and aggregate content as well as the temperature, which were not discussed in this paper. T2 - 3rd Symposium on Knowledge Exchange for Young Scientists (KEYS) CY - Johannesburg, South Africa DA - 26.06.2017 KW - Stabilising agent KW - Limestone filler KW - Cement 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 - 143 EP - 146 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-41000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Priebe, Nsesheye Susan ED - Schmidt, Wolfram T1 - Why Africa can spearhead innovative and sustainable cement and concrete technologies globally N2 - The perception of concrete in the society as well as in the politics is rather negative. This becomes obvious in the fact that the phrase “concrete jungle” has become synonym for hapless living with no perspectives. In politics and research funding, it is also not easy to create a broader audience, since concrete is falsely considered as old-fashioned material that is sufficiently understood today and does not need further considerations, particularly compared to allegedly newer materials. However, particularly since the last two decades the technology has completely changed. Binders of today are no more the same binders as used before, and concrete mixture compositions of today diverge quite significantly from compositions in the past. There is little understanding world-wide about that. This causes that potentials the concrete technology bears are wasted. In the broadly found opinion that concrete is old-fashioned and ugly, it is ignored that architectural sins are not inherent to the material, which actually is extremely versatile and CO2-friendly compared to all other construction materials available. It is also ignored that 98% of the outer Earth’s crust are made of the elements cement and concrete are made from, and therefore it will be an illusion to believe that the complementary 2% can create materials to develop regions and infrastructures in less developed areas in the world. For betterment in Africa the infrastructural development should have highest priority, since poor connections between settlements are responsible for enormous Price increases [2], and urban traffic congestion is responsible for an incredible loss of productivity. It is not unrealistic to assume that earners that are dependent on a car get stuck in traffic about 3-4 hours per day in cities like Lagos, Nairobi or Dar es Salaam. However, the traffic congestions do not only affect the car owners negatively but the living of the entire urban population every day. Besides infrastructure, housing should be the other priority, since a large part of the African population does not live in adequate condition. This is a societal problem, since unequal Distribution of wealth is a major driving force for instability in societies. The latter has a global impact, since 8 many phenomena that can be observed all over the world such as political radicalism, xenophobia, terrorism, and migration can often be linked to instable societies. However, the importance of infrastructure has an even wider range. Most African countries go through a change process recently. In order to strengthen very positive perspectives, the focus in politics and research funding is put on issues such as agriculture, energy, and health, which are without doubt extremely important issues. However, it is typically overlooked that all enhancements in these areas can only become effective, when an infrastructure is created to support the implementation of better concepts. Mobility is the key to a prosperous future, and mobility can only be granted by infrastructural construction activities. Hence, compared to many other regions in the world, cement and concrete technologies have a significantly higher relevance in Africa. T2 - 2nd Symposium on Knowledge Exchange for Young Scientists (KEYS) CY - Accra, Ghana DA - 7.6.2016 KW - Cement KW - Concrete KW - Sustainability KW - Carbon dioxide KW - Polysaccharides KW - Cassava KW - Rheology PY - 2016 SN - 978-3-9817853-1-9 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 2 SP - 7 EP - 19 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-40974 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - 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 - Schmidt, Wolfram ED - Beushausen, Hans T1 - Application of a cusum control system for enhanced robustness of the flow properties of self-compacting concrete N2 - Control chart systems are used in quality management systems to keep production processes stable. In concrete production they are often applied for the control of the compressive strength. The most efficient control chart systems are cumulated sums (cusum), which help to observe deviations from a targeted value. Unlike alternative observation chart systems that focus on process data evaluation, cusum observations react very rapidly on systematic process changes in processes. Therefore, the cusum method is particularly suitable if immediate counteractions have to be taken, like in the case of fresh concrete properties of self-compacting concrete (SCC), which can have severe influences on the durability and mechanical strength of concrete. The rheology of SCC can be affected by an enormous variety of influencing factors, from raw material properties to handling or environmental temperature. The present study shows that regardless of the material based influencing parameter for a rheology change, a steady slump flow can be achieved only by adding supplementary superplasticizer in case of loss of flow and adding stabilising agent (ST) in case of increased flow if the respective V-mask indicates a systematic change. A reference SCC was artificially manipulated in order to achieve realistic experimental data for flowability and flowability changes due to changes in the raw material properties. The results point out that productions with applied cusum methods were capable of keeping the target slump flow deviation within approximately 1% only, while productions without applied cusum method deviated up to 14% and more from the target. T2 - fib Symposium 2016. Performance-Based Approaches for Concrete Structures. CY - Cape Town, South Africa DA - 21.11.2016 KW - Concrete KW - Self-compacting concrete KW - cusum KW - control chart KW - quality control KW - robustness PY - 2016 SN - 978-2-88394-121-2 SP - 106-1 EP - 106-10 PB - Fédération internationale du béton ( fib) CY - Lausanne, Switzerland AN - OPUS4-40976 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram ED - Banjad Pecur, Ivana ED - Baricevic, Ana ED - Stirmer, Nina ED - Bjegovic, Dubravka T1 - Potentials for sustainable cement and concrete technologies - Comparison between Africa and Europe N2 - The fundamental knowledge about cement and concrete has made enormous progress over the last decades, and today it would be possible to find optimised sustainable concrete solutions tailored for every given boundary framework and raw material supply. However, this knowledge barely finds implementation into practice despite the urgent global need to minimise carbon emissions and energy consumption. A major reason is that most concrete developments were historically made in the northern hemisphere, where today over-regulations and stagnating market perspectives slow down innovation drive towards higher sustainability. In most African countries, however, sustainable building is simply an urgent real-life problem. The demand for building is enormous, Standard solutions are not an option, and the pool of innovative local raw materials and concrete concepts is enormous. The paper provides a comprehensive comparison between the boundary frameworks of Europe and Africa, and it is explained why local African solutions shall be given priority over imported solutions. Examples of local African concrete solutions are given, and ideas for a rapid implementation are developed. Most of the potentially useful materials such as agricultural ashes, natural and calcined pozzolans, polysaccharides, etc. have not yet been subject to intensive research to date. Therefore, it is not unlikely to assume that with an open mind for non-Standard solutions, combined with creativity and particularly knowledge and awareness, the next generation of innovative and sustainable concretes will be developed and applied on the African continent. Therefore, the conclusion is that particularly the African continent provides the best starting position to develop better and more sustainable concrete solutions than anywhere else in the world. Hence, Africa can become a global pioneer in green cement and concrete technology with impact to the entire world. N2 - Posljednih desetljeća načinjen je golem napredak u temeljnim znanjima o cementu i betonu. Danas bi bilo moguće naći rješenja za optimalni održivi beton primjeren svakom danom okviru i dobavi sirovina. Međutim, takvo znanje jedva da se primjenjuje u praksi unatoč hitnoj globalnoj potrebi smanjenja na najmanju mjeru emisija ugljika i potrošnje energije. Glavni je razlog što je većina razvoja u području betona tijekom povijesti načinjena u sjevernoj hemisferi gdje danas preregulacija i perspektiva stagnirajućeg tržišta usporavaju inovacije ka većoj održivosti. Međutim, u većini afričkih zemalja održiva gradnja jednostavno je hitni problem svakodnevice. Zahtjevi za gradnjom su golemi, obična rješenja nisu opcija, rezerve inovativnih lokalnih sirovina i mogućnosti primjene betona su golemi. U radu se daje sveobuhvatna usporedba graničnih okosnica Europe i Afrike, a objašnjeno je zašto se lokalnim afričkim rješenjima mora dati prioritet pred uvezenim rješenjima. Većina potencijalno korisnih materijala kao što su pepeli iz poljoprivrede, prirodni i kalcinirani pucolani, polisaharidi itd. do danas nisu bili predmetom intenzivnih istraživanja. Stoga nije nevjerojatno pretpostaviti da će se Nova generacija inovativnih i održivih betona razviti i primijeniti na afričkom kontinentu uz otvorenost prema nestandardnim rješenjima i u kombinaciji s kreativnošću i posebno znanjem i sviješću. Stoga je zaključeno da naročito afrički kontinent osigurava najbolju početnu poziciju za razvoj boljih i održivijih betona nego bilo gdje u svijetu. Prema tome Afrika može postati svjetski pionir u tehnologiji zelenoga cementa i betona s utjecajem na cijeli svijet. T2 - 1st International Conference on Construction Materials for a Sustainable Future CY - Zadar, Croatia DA - 19.4.2017 KW - Africa KW - Sustainability KW - Cement KW - Concrete KW - Admixtures KW - Carbon emissions PY - 2017 SN - 978-953-8168-04-8 SP - 829 EP - 835 CY - Zagreb, Croatia AN - OPUS4-40977 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Tchetgnia Ngassam, Inès A1 - Mbugua, Rose A1 - Adisa Olonade, Kolawole T1 - Promising bio-based rheology modifying agents for concrete N2 - Today, concrete engineers can vary consistencies between very stiff and self-compacting. The possibility to tailor rheological properties of concrete eventually opened up the path to multiple new technologies, where design criteria are no longer limited to the Young’s modulus and the compressive strength, but often comprise additional added value. It can therefore be concluded that the capability to control the rheology of concrete systems can be considered as the catalyst for concrete innovations such as polymer modified cementitious composites (PCC) self-compacting concrete (SCC), high-performance concrete (HPC), ultra-high performance concrete (UHPC) or strain hardening cement based composites (SHCC). In the same way rheology modifying admixtures will become key parameters in mastering the challenges of the next decades such as: - Additive manufacturing/3D-printing - Overcoming pumping height limitations - Casting at extreme temperatures - Tailored rheology at delivery In many regions in the Southern hemisphere, and particularly in Africa, the effective use of chemical admixtures for concrete could significantly contribute to solve problems induced by the challenging climatic conditions, but particularly in Africa it is difficult to use them, due to lacking local supply and supply infrastructure. For Africa, concrete admixtures are largely shipped or transported from Europe, the Arabian Peninsula, or Asia. 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 not a large variety of products available in the market. However, bio-based chemicals have been used in construction for ages effectively. 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. Today, the use of petrol based polycarboxylate ether superplasticizers has become quite common in concrete technology due to their versatility, but their uncomplicated and cost efficient availability is limited in most countries in Africa. However, alternatives are available, which can be found in many regions. Plant extracts have been used to modify the properties of concrete for long time. These plants are typically regionally abundantly available, cheap, and they are environmental friendly. They do not require special caring for seedlings, weeding or manuring to grow since they grow wildly. The talk will present an overview of various options for rheology modifying admixtures, that can be found in nature, and that may become a real alternative, once their interaction within the complex cementitious system is well understood. T2 - Rheologie komplexer Fluide: Theorie, Experiment und Anwendung, DRG/ProcessNet | Gemeinsame Diskussionstagung CY - Berlin, Germany DA - 13.3.2017 KW - Africa KW - Cement KW - Concrete KW - Admixtures KW - Polysaccharides KW - Cassava KW - Starch KW - Triumfetta Pendrata A. Rich KW - Nkui PY - 2016 AN - OPUS4-40979 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -