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 - 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 - 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 - 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 - JOUR A1 - Vasilic, Ksenija A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A1 - Roussel, N. T1 - Numerical modelling of SCC flow through reinforced sections T1 - Numerische Simulation des Fließverhaltens von SVB durch bewehrte Querschnitte N2 - The study introduces the porous medium model for the simulation of concrete flow through highly-reinforced sections. It shows that numerical simulations can predict concrete behavior during casting and help to avoid expensive mistakes. N2 - Bei der hier dargestellten Untersuchung wird das Modell des porösen Mediums auf die Simulation des Fließverhaltens von Beton durch Querschnitte mit hohem Bewehrungsgrad angewandt. Dabei zeigt sich, dass mit Hilfe numerischer Simulationen das Verhalten des Betons während der Betonage prognostiziert und kostspielige Fehler vermieden werden können. PY - 2015 SN - 0373-4331 SN - 1865-6528 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 81 IS - 03 SP - 50 EP - 55 PB - Bauverl. CY - Gütersloh AN - OPUS4-33151 LA - mul 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 N2 - Concrete can play a major role in overcoming the challenges of construction in sub-Saharan Africa where various factors negatively affect the quality and durability of concrete structures. Self-compacting concrete (SCC) is a practical solution to separate concrete properties from these parameters. Conditions on most African construction sites militate against producing high-quality concrete; SCC’s exceptional workability outweighs any of its limitations. This article examines how to introduce robust, reliable, cost-efficient SCC into practice as a pre-mixed dry compound incorporating local materials like natural pozzolans, cassava starch and lignosulphonate. 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 T1 - Einfluss der Fließmittelmodifikation auf die Verarbeitungseigenschaften fließfähiger Betone - Hintergründe und Optimierungspotential N2 - Durch die Möglichkeit, die Konsistenz weitgehend vom Wasserzementwert zu entkoppelt, stellen verflüssigende Zusatzmittel ein starkes Werkzeug zur Verbesserung der Betontechnologie dar. Deswegen ermöglichen auch erst neuere Entwicklungen im Bereich der Fließmittel betontechnologische Innovationen wie den selbstverdichtenden Beton, hochfesten und ultrahochfesten Beton. Eine besondere Bedeutung haben Polycarboxylatether-Fließmittel. Diese sind in einer sehr großen Vielfalt und mit einer großen Bandbreite an Leistungseigenschaften am Markt erhältlich. Allerdings werden aufgrund der Vielseitigkeit Betone mit hohen Fließmittelgehalten auch sehr anfällig gegenüber äußeren Einflüssen, so dass Veränderungen in den Umgebungsbedingungen ungewünschte Effekte hervorrufen können. Folglich erfordern Betone mit Rießmitteln ein hohes Maß an Expertise, die nicht immer in der Praxis vorhanden ist. Der vorliegende Artikel gibt einen Überblick über die Wirkungsweisen von Fließmitteln und wie deren Leistungseigenschaften genutzt werden kann, um betontechnologische Fragestellungen optimal zu lösen. T2 - Fachtagung Betonbau aktuell 2014 CY - Apolda, Germany DA - 13.02.2014 PY - 2014 SP - 1 EP - 7 AN - OPUS4-30945 LA - deu 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 - Olonade, Kolawole Adisa A1 - Tchetgnia Ngassam, Ines Leana A1 - Mbugua, Rose A1 - Athman Mwende, Carol A1 - Kühne, Hans-Carsten ED - Ludwig, Horst-Michael T1 - Pflanzenbasierte Betonzusatzmittel für Hochleistungsbeton N2 - Während für die Bauwirtschaft in den meisten Ländern der nördlichen Halbkugel die Instandhaltung bestehender Strukturen und Infrastruktur im Vordergrund steht, geht es in vielen Ländern der Südhalbkugel in der Hauptsache um die Schaffung von Bauwerken und Infrastruktur zur Verwirklichung angemessener Lebensbedingungen, was wiederum das schnelle Wirtschaftswachstum weiter befeuert. Beton ist als Massenbaustoff, trotz landläufig anderer Bewertung, aufgrund seines im Vergleich zu anderen Baustoffen günstigen CO2-Footprints und der globalen Verfügbarkeit hierbei aktuell ohne Alternative. Allerdings ist Beton nach Wasser das am zweithäufigsten genutzte Produkt auf Erden [1] und die globale Nachfrage und Produktion steigt dramatisch. Dies hat Konsequenzen für das globale Klima, denn gerade die als Bindemittel eingesetzten Portlandzemente verursachen bei ihrer Herstellung selbst unter modernsten Produktionsbedingungen große Mengen an CO2. Deshalb müssen für zukünftige nachhaltigere Technologien neuartige Betone entwickelt werden, die bei gleicher oder verbesserter Leistungsfähigkeit, einen geringeren Bedarf an Portlandzement aufweisen. Um den CO2-Ausstoß, der mit der Betonherstellung verbunden ist zu minimieren, müssen Anteile an Portlandzement im Bindemittel reduziert und durch nachhaltigere Ersatzstoffe ausgetauscht werden. Darüber hinaus muss das eingesetzte Bindemittel im Beton so effizient wie möglich ausgenutzt werden. Das heißt, ein Bauteil oder Bauwerk sollte gerade so viel Bindemittel enthalten, wie für die Tragfähigkeit und Dauerhaftigkeit erforderlich ist. Hierfür erscheint der Einsatz von leistungsfähigen bauchemischen Produkten unumgänglich. Diese können zum einen die veränderten Verarbeitungseigenschaften, die Zementersatzstoffe mit sich bringen, ausgleichen und gleichzeitig helfen, den Gesamtwassergehalt zu minimieren, so dass das Bindemittel seine maximale Leistungsfähigkeit erzielt. Fließmittel sind aktuell die wichtigsten Zusatzmittel für Beton. Sie reduzieren den Wasserbedarf und ermöglichen, Zement im Beton effizienter auszunutzen. Darüber hinaus sind Stabilisierer wichtig zur Erhöhung der Robustheit, insbesondere im Hinblick auf die bautechnischen Herausforderungen der Zukunft – vom Pumpen über weite Distanzen, dem Spritzen, dem Betonieren bei extremen Klimabedingungen bis hin zum 3D-Druck. T2 - ibausil CY - Weimar, Germany DA - 12.09.2018 KW - Bauchemie KW - Zusatzmittel KW - Rheologie KW - Polysaccharide KW - Akaziengummi KW - Triumfetta Pendrata A. Rich PY - 2018 SN - 978-3-00-059950-7 VL - 20 SP - 1-874 EP - 1-885 CY - Weimar AN - OPUS4-47048 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 - 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 - JOUR A1 - Kossatz, Philipp A1 - Mezhov, Alexander A1 - Andresen, Elina A1 - Schmidt, Wolfram A1 - Resch-Genger, Ute T1 - Application of fluorescence spectroscopy for the monitoring of cement hydration N2 - Lanthanide-based upconversion nanoparticles (UCNPs) with size- and morphology-dependent emission patterns, composed of narrow bands of varying intensity in the ultraviolet, visible, near-infrared, and short-wave infrared wavelength region, were synthesized via a thermal decomposition approach under inert atmosphere. Subsequently, differently sized UCNPs were incorporated into ordinary Portland cement to study their stability in the harsh cementitious environment and assess their potential for the probing and monitoring of cement hydration. Microenvironment-specific changes in the emission properties of these inorganic luminophores were utilized to study and probe changes of physico-chemical parameters during cement hydration. Isothermal calorimetry was employed to better understand the influence of luminophore addition on cement hydration kinetics and for the correlation with the results of the optical studies. T2 - 12th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete (ICCM 2024) CY - Toulouse, France DA - 23.06.2024 KW - Luminescence KW - Optical probe KW - Cement hydration PY - 2024 UR - https://www.iccm2024.com/ SP - 441 EP - 446 CY - Toulouse, France AN - OPUS4-62119 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Govin, A. A1 - Bartholin, M.-C. A1 - Schmidt, Wolfram A1 - Grosseau, P. T1 - Combination of superplasticizers with hydroxypropyl guar, effect on cement-paste properties N2 - Viscosity-modifying agent (VMA) are used in several applications of concrete, such as underwater concrete, Self-Compacting Concrete (SCC) or Self-Levelling Underlayments (SLU) in order to improve the washout resistance and the stability. The study focuses on the modifications of cement pastes properties implied when a VMA (hydroxypropyl guars or HPG) and a superplasticizer are introduced together. For reaching this objective, two chemically different polycarboxylate-based superplasticizers (PCE) and two HPGs exhibiting different molar substitution ratios (MSHP), were studied. A method, combining total organic carbon and size exclusion chromatography, was developed in order to quantify the adsorption of the both admixtures. The adsorption of HPGs appears being significantly lowered by the presence of PCE, while only the adsorption of the less charged PCE is slightly affected by the HPG. As consequence, strong modifications of the rheological properties of cement pastes were noticed when HPG and PCE are combined. The desorption of HPG leads to higher yield stress and residual viscosity than with PCE alone. KW - Pore solution KW - Admixture KW - Rheology KW - Adsorption KW - Polymers PY - 2019 DO - https://doi.org/10.1016/j.conbuildmat.2019.04.137 VL - 215 SP - 595 EP - 604 PB - Elsevier Ltd. AN - OPUS4-49298 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 - JOUR A1 - Lorenzoni, Renata A1 - Mezhov, Alexander A1 - Fritsch, Tobias A1 - Schmidt, Wolfram A1 - Kruschwitz, Sabine T1 - Effect of Biochar on the Microstructure and Mechanical Response of Cement Paste N2 - The use of biochar as a supplementary cementitious material is proposed to reduce the global greenhouse gas emissions. Since biochar is non-reactive, has a low density and complex porosity, its incorporation into cementitious materials results in microstructural changes and consequently affects the mechanical response. This work advances the mechanical response understanding of Portland cement composites with 0, 5, and 25 volume percent (vol%) of cement replaced with biochar by using in-situ computed tomography, correlating with the microstructural changes analyzed by HFC, gas sorption, MIP, gas sorption, and NMR. The results highlight the influence of the mesoscale structure on mechanical responses and relate the lack of loss of mechanical strength at 5 vol% replacement to the compensation of decreasing larger pores with biochar addition. At 25 vol% replacement, the amount of weakened zones in the paste due to biochar overcompensates the positive effect of the reduction in larger pores, resulting in a loss of mechanical properties. Hence, small amounts of biochar can enhance the microstructure, but the reduction of the carbon footprint is limited. T2 - 24th International Conference on Composite Materials (ICCM24) CY - Baltimore, Maryland, USA DA - 04.08.2024 KW - Supplementary cementitious materials KW - Biochar KW - Microstructure KW - In-situ computed tomography KW - Mechanical proprieties. PY - 2024 DO - https://doi.org/10.14359/51742027 VL - 362 SP - 1020 EP - 1032 PB - International Concrete Abstracts Portal AN - OPUS4-62115 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - Effects of the characteristics of high range water reducing agents and the water to powder ratio on rheological and setting behavior of self-consolidating concrete N2 - To design robust self-consolidating concrete (SCC) for various environmental conditions, it is essential to understand the relevant mechanisms that control the flow performance. This paper depicts how high range water reducing agents (HRWRAs) interact with clinker and hydration phases, and it discusses the important role of the charge density of polycarboxylic HRWRAs in the way the rheology is affected. Based on the rheometric investigations on SCC mixture compositions with different water to powder ratios (w/p) and observations of their pastes' Vicat setting times, the study shows that increasing charge densities of the HRWRA and decreasing w/p reduce the flow retention and have lesser retarding effect on the setting. Based on the test results and discussions optimization procedures for the mixture composition and the HRWRA modification are suggested to achieve optimized performance for varying environmental situations and highest robustness for specific conditions. KW - Polycarboxylate KW - HRWRA KW - Robustness KW - Rheology KW - Self-consolidating concrete PY - 2014 DO - https://doi.org/10.1520/ACEM20130094 SN - 2165-3984 VL - 3 IS - 2 SP - 1 EP - 15 PB - ASTM International CY - West Conshohocken, Pa., USA AN - OPUS4-30388 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram 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 -