TY - JOUR A1 - Mezhov, Alexander A1 - Zhang, K. A1 - Schmidt, Wolfram T1 - Interactions of Biobased Rheology Modifying Agents with Superplasticizer in Cement Paste JF - Construction Technologies and Architecture N2 - Organic admixtures are an indispensable component of modern concrete. Thus, their purposeful application is not only technically and economically viable but in addition an inevitable tool to make concrete more environmentally friendly. In this context, the use of polysaccharides has increasingly gained interest in the built environment as sustainable resource for performance enhancement. However, due to its origin, biopolymers possess a vast variety of molecular structures which can result in incompatibilities with other polymers present in concrete, such as superplasticizers. The present study highlights effects of the joint application of different types of starches and polycarboxylates with respect to their influence on cement hydration and structural build-up of cement pastes. KW - Polysaccharides KW - Superplasticizers KW - Hydration KW - Cement PY - 2022 DO - https://doi.org/10.4028/www.scientific.net/CTA.1.563 SN - 2674-1237 SP - 563 EP - 568 PB - Trans Tech Publications Ltd, Switzerland CY - Basel, Switzerland. AN - OPUS4-58325 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 T2 - Proceedings of the 1st International Conference on Construction Materials for a Sustainable Future 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 - Leinitz, Sarah A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten ED - Priebe, Nsesheye Susan T1 - Influence of stabilising agents on limestone filler and cement pastes T2 - Proceedings of the 3rd symposium knowledge exchange for young scientists (KEYS) - Applicable cement and concrete technology for sub-Saharan Africa - International cooperation, innovation, research and capacity building 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 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 - JOUR A1 - Schmidt, Wolfram A1 - Brouwers, H.J.H. A1 - Kühne, Hans-Carsten A1 - Meng, Birgit T1 - The working mechanism of starch and diutan gum in cementitious and limestone dispersions in presence of polycarboxylate ether superplasticizers JF - Applied rheology N2 - Polysaccharides provide high potential to be used as rheology modifying admixtures in mineral binder systems for the construction industry such as concrete or mortar. Since superplasticizers have become state of technology, today, concrete is more and more adjusted to flowable consistencies. This often goes along with the risk of segregation, which can be effectively avoided by adding stabilising agents supplementary to superplasticizers. Stabilising agents are typically based on polysaccharides such as cellulose, sphingan gum, or starch. Starch clearly distinguishes in its effect on rheology from other polysaccharides, mainly due to the strong influence of amylopectin on the dispersion and stabilisation of particles. Based on rheometric investigations on cementitious and limestone based dispersions with different volumetric water to solid ratios, the mode of operation of modified potato starch is explained in comparison to a sphingan gum. It is shown that the stabilising effect of starch in a coarsely dispersed system is mainly depending upon the water to solid ratio and that above a certain particle volume threshold starch mainly affects the dynamic yield stress of dispersions, while plastic viscosity is affected only to a minor degree. Sphingans operate more independent of the particle volume in a coarsely dispersed system and show significantly higher effect on the plastic viscosity than on the yield stress. In systems incorporating superplasticizers, influences of both stabilising agents on yield stress retreat into the background, while both observed polysaccharides maintain their effect on the plastic viscosity. KW - Cement KW - Limestone KW - Rheology KW - Stabilising agent KW - Coarsely dispersed systems KW - Diutan gum KW - Starch ether PY - 2013 DO - https://doi.org/10.3933/ApplRheol-23-52903 SN - 1430-6395 SN - 0939-5059 VL - 23 IS - 5 SP - 52903-1 EP - 52903-12 PB - Kerschensteiner CY - Lappersdorf AN - OPUS4-29932 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 T2 - GDCh-Monograph 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 - 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 T2 - Rheologische Messungen an Baustoffen 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 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of rheology modifying admixtures on early hydration of cementitious suspensions T2 - PAPERS AND POSTERS PROCEEDINGS 15th International Congress on the Chemistry of Cement 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 - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of Rheology Modifying Admixtures on Hydration of Cementitious Suspensions T2 - Sixth International Symposium on Nanotechnology in Construction, Technology Transfer in Action 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 -