TY - CONF A1 - Schmidt, Wolfram T1 - Peculiarities of African Cement and Condrete Markets - Challenges and Opportunities T2 - Global Issues in Concrete Construction CY - Johannesburg, South Africa DA - 2013-09-18 PY - 2013 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-29922 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Zum Einfluss der Fließmittelmodifikation auf die Verarbeitungseigenschaften fließfähiger Betone - Hintergründe und Optimierungspotential T2 - betonbau.aktuell 2014 CY - Apolda, Germany DA - 2014-02-13 PY - 2014 AN - OPUS4-30831 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Self-Compacting concrete-Past, Present and Futere T2 - Totally Concrete Expo Conference 2014 CY - Johannesburg, South Africa DA - 2014-05-26 PY - 2014 AN - OPUS4-30829 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Quality Control in Concrete Production T2 - Public Seminar at the School of Civil and Environmental Engineering CY - Johannesburg, South Africa DA - 2014-05-29 PY - 2014 AN - OPUS4-30833 LA - deu 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 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 - 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 - CONF A1 - Schmidt, Wolfram T1 - Recent Developments and Perspectives Regarding the Standardisation and Quality Surveillance of Cement in the East, Central and South African Region T2 - XIII ICCC - International Congress on the Chemistry of Cement CY - Madrid, Spain DA - 2011-07-03 PY - 2011 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-24020 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - Rheological optimisation for flowable concrete for subsaharan environmental conditions T2 - 1st International RILEM Conference on Rheology and Processing of Construction Materials and 7th RILEM Conference on Self-Compacting Concrete CY - Paris, France DA - 2013-09-02 PY - 2013 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. AN - OPUS4-29924 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram T1 - The African-European SPIN Expert Network - Objectives and Experiences T2 - Workshop zur Antragstellung im ACP-EU Cooperation Programme in Science and Technology II (ACP S&T II) CY - Bonn, Germany DA - 2012-12-04 PY - 2012 AN - OPUS4-27266 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -