@article{PartschefeldTutalHalmansederetal., author = {Partschefeld, Stephan and Tutal, Adrian and Halmanseder, Thomas and Schneider, Jens and Osburg, Andrea}, title = {Investigations on Stability of Polycarboxylate Superplasticizers in Alkaline Activators for Geopolymer Binders}, series = {Materials}, volume = {2023}, journal = {Materials}, number = {Volume 16, issue 15, article 5369}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma16155369}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20231026-64809}, pages = {1 -- 14}, abstract = {Calcined clays are interesting starting materials to be used as SCMs (supplementary cementitious materials) in cements or to be converted to geopolymers by activation with a high alkaline activator. The adjustment of the properties in the fresh state, especially regarding the consistency of these binders, is almost exclusively achieved by the addition of water, since commercially available superplasticizers seem to be ineffective in low-calcium geopolymer systems. The aim of this study was a systematic investigation of various PCE (polycarboxylate ester/ether) superplasticizers (methacrylate ester PCE: MPEG, isoprenol ether PCE: IPEG, methallyl ether PCE: HPEG) with respect to their stability in different alkaline activators (NaOH, KOH, sodium and potassium silicate solutions). The effectiveness of superplasticizers (SPs) in low-calcium geopolymer binders was verified by rheological tests. Size exclusion chromatography was used to investigate if structural degradation of the superplasticizers occurs. The investigated PCE superplasticizers showed a thickening effect in the low-calcium geopolymer system. Depending on the alkalinity of the activator solution, a degradation process was detected for all the PCEs investigated. The side chains of the PCEs are cleaved off the backbone by basic ester and ether hydrolysis. The highest degree of degradation was found in sodium and potassium silicate solutions. In alkaline hydroxide solutions, the degradation process increases with increasing alkalinity.}, subject = {Geopolymere}, language = {en} } @article{WiegandOsburg, author = {Wiegand, Torben and Osburg, Andrea}, title = {Synthesis, Curing and Thermal Behavior of Amine Hardeners from Potentially Renewable Sources}, series = {Polymers}, volume = {2023}, journal = {Polymers}, number = {volume 15, issue 4, article 990}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/polym15040990}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230524-63745}, pages = {1 -- 12}, abstract = {Research into bio-based epoxy resins has intensified in recent decades. Here, it is of great importance to use raw materials whose use does not compete with food production. In addition, the performance of the newly developed materials should be comparable to that of conventional products. Possible starting materials are lignin degradation products, such as vanillin and syringaldehyde, for which new synthesis routes to the desired products must be found and their properties determined. In this article, the first synthesis of two amine hardeners, starting with vanillin and syringaldehyde, using the Smiles rearrangement reaction is reported. The amine hardeners were mixed with bisphenol A diglycidyl ether, and the curing was compared to isophorone diamine, 4-4′-diaminodiphenyl sulfone, and 4-Aminonbenzylamine by means of differential scanning calorimetry. It was found that the two amines prepared are cold-curing. As TG-MS studies showed, the thermal stability of at least one of the polymers prepared with the potentially bio-based amines is comparable to that of the polymer prepared with isophorone diamine, and similar degradation products are formed during pyrolysis.}, subject = {Epoxide}, language = {en} } @article{KleinerRoesslerVogtetal., author = {Kleiner, Florian and R{\"o}ßler, Christiane and Vogt, Franziska and Osburg, Andrea and Ludwig, Horst-Michael}, title = {Reconstruction of calcium silicate hydrates using multiple 2D and 3D imaging techniques: Light microscopy, μ-CT, SEM, FIB-nT combined with EDX}, series = {Journal of Microscopy}, volume = {2021}, journal = {Journal of Microscopy}, publisher = {John Wiley \& Sons Ltd}, address = {Oxford}, doi = {10.1111/jmi.13081}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220106-45458}, pages = {1 -- 6}, abstract = {This study demonstrates the application and combination of multiple imaging techniques [light microscopy, micro-X-ray computer tomography (μ-CT), scanning electron microscopy (SEM) and focussed ion beam - nano-tomography (FIB-nT)] to the analysis of the microstructure of hydrated alite across multiple scales. However, by comparing findings with mercury intrusion porosimetry (MIP), it becomes obvious that the imaged 3D volumes and 2D images do not sufficiently overlap at certain scales to allow a continuous quantification of the pore size distribution (PSD). This can be overcome by improving the resolution and increasing the measured volume. Furthermore, results show that the fibrous morphology of calcium-silicate-hydrates (C-S-H) phases is preserved during FIB-nT. This is a requirement for characterisation of nano-scale porosity. Finally, it was proven that the combination of FIB-nT with energy-dispersive X-ray spectroscopy (EDX) data facilitates the phase segmentation of a 11 × 11 × 7.7 μm3 volume of hydrated alite.}, subject = {Zementklinker}, language = {en} } @inproceedings{KleinerWiegandOsburg, author = {Kleiner, Florian and Wiegand, Torben and Osburg, Andrea}, title = {Eigenschaftsentwicklung epoxidharzmodifizierter M{\"o}rtel auf Zementbasis bei unterschiedlichen klimatischen Bedingungen}, series = {Tagung Bauchemie der GDCh-Fachgruppe Bauchemie, 18.-20. September 2017 in Weimar}, booktitle = {Tagung Bauchemie der GDCh-Fachgruppe Bauchemie, 18.-20. September 2017 in Weimar}, publisher = {Gesellschaft Deutscher Chemiker}, isbn = {978-3-947197-02-6}, doi = {10.25643/bauhaus-universitaet.4506}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211004-45067}, pages = {4}, abstract = {Zur Erstellung von dekorativen Plastiken sollten M{\"o}rtel entwickelt werden, die eine hohe Biegezugfestigkeit aufweisen und eine breite Palette von Konsistenzen f{\"u}r verschiedene Anwendungsarten, wie Gießen, Spachteln oder Stampfen abdecken. Als Basis f{\"u}r die Rezepturen wurde ein niedrigviskoses Epoxidharzsystem gew{\"a}hlt, dessen Aminh{\"a}rter einen Wasseranteil von 44 \% beinhaltet. Dies erm{\"o}glichte es, durch Wasserzugabe verschiedene Viskosit{\"a}ten einzustellen. Um dieses Wasser in massiveren Bauteilen zu binden, wurde neben Sand auch Zement als F{\"u}llstoff eingesetzt. Die erstellten Rezepturen zeigten nach 56 Tagen hohe Druckfestigkeiten von {\"u}ber 50 N/mm². Mit zunehmendem Epoxidharzgehalt ergaben sich zwar steigende Biegezugfestigkeiten, jedoch unter Laborlagerung auch gr{\"o}ßere L{\"a}ngen{\"a}nderungen. Diese konnten durch den Einsatz eines PCE-Fließmittels, PVA-Kurzfasern und einer optimierten Sieblinie verringert werden. Das Fließmittel verl{\"a}ngerte die Erh{\"a}rtungszeiten jedoch auf bis zu 1,5 Tage. Zur Ermittlung der Dauerhaftigkeit des Materials wurde es f{\"u}r drei Wochen Temperaturen von -20 bis +60 °C, einer k{\"u}nstlichen Sonnenbestrahlung sowie k{\"u}nstlicher Beregnung ausgesetzt. Im Vergleich zur Laborlagerung ergab sich bei steigendem Epoxidharzanteil ein geringerer Schwund, w{\"a}hrend die Biegezugfestigkeit der Probek{\"o}per nur geringf{\"u}gig abnahm. Rasterelektronenmikroskopische Untersuchungen zeigten, dass auch bei geringeren Epoxidharzzus{\"a}tzen St{\"o}rungen der Zementhydratation auftraten. Weiterhin zeigen sich bei geringen Epoxidharzzus{\"a}tzen in der Matrix kugelf{\"o}rmige Einschl{\"u}sse, die von dispergierten Epoxidharzpartikeln stammen.}, subject = {Bauchemie}, language = {de} } @inproceedings{SchirmerKleinerOsburg, author = {Schirmer, Ulrike and Kleiner, Florian and Osburg, Andrea}, title = {Objektive Oberfl{\"a}chenbewertung von (P)SCC-Sichtbeton mittels automatisierter Analyse von Bilddaten}, series = {Tagung Bauchemie der GDCH-Fachgruppe Bauchemie, 30. September - 2. Oktober 2019 in Aachen}, booktitle = {Tagung Bauchemie der GDCH-Fachgruppe Bauchemie, 30. September - 2. Oktober 2019 in Aachen}, publisher = {Gesellschaft Deutscher Chemiker}, isbn = {978-3-947197-13-2}, doi = {10.25643/bauhaus-universitaet.4510}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211004-45104}, pages = {8}, abstract = {Sichtbeton ist aufgrund seiner Vielf{\"a}ltigkeit in der Formgebung eines der am meisten verbreiteten Gestaltungsmittel der modernen Architektur und optimal f{\"u}r neue Bauweisen sowie steigende Anforderungen an das Erscheinungsbild {\"o}ffentlicher Bauwerke geeignet. Die Herstellung qualitativ hochwertiger Sichtbetonoberfl{\"a}chen h{\"a}ngt im hohen Maße von den Wechselwirkungen zwischen Beton und Trennmittel, zwischen Trennmittel und Schalmaterial, sowie von der Applikationsart und -menge des Trennmittels ab. In Laborversuchen wurden diese Einfl{\"u}sse auf die Sichtbetonoberfl{\"a}chen eines polymermodifizierten selbstverdichtenden Betons (PSCC) im Vergleich zu einem herk{\"o}mmlichen selbstverdichtenden Beton (SCC) untersucht. Im Rahmen dieser Arbeiten wurde eine Methode zur Beurteilung der Sichtbetonqualit{\"a}t entwickelt, mit welcher Ausschlusskriterien, wie maximale Porosit{\"a}t und Gleichm{\"a}ßigkeit, objektiv und automatisiert bestimmt werden k{\"o}nnen. Ver{\"a}nderungen dieser Werte durch Witterungseinfl{\"u}sse ließen zudem erste R{\"u}ckschl{\"u}sse auf die Dauerhaftigkeit der Sichtbetonoberfl{\"a}chen zu.}, subject = {Sichtbeton}, language = {de} } @article{TutalPartschefeldSchneideretal., author = {Tutal, Adrian and Partschefeld, Stephan and Schneider, Jens and Osburg, Andrea}, title = {Effects of Bio-Based Plasticizers, Made From Starch, on the Properties of Fresh and Hardened Metakaolin-Geopolymer Mortar: Basic Investigations}, series = {Clays and Clay Minerals}, volume = {2020}, journal = {Clays and Clay Minerals}, number = {volume 68, No. 5}, publisher = {Springer}, address = {Heidelberg}, doi = {10.1007/s42860-020-00084-8}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210804-44737}, pages = {413 -- 427}, abstract = {Conventional superplasticizers based on polycarboxylate ether (PCE) show an intolerance to clay minerals due to intercalation of their polyethylene glycol (PEG) side chains into the interlayers of the clay mineral. An intolerance to very basic media is also known. This makes PCE an unsuitable choice as a superplasticizer for geopolymers. Bio-based superplasticizers derived from starch showed comparable effects to PCE in a cementitious system. The aim of the present study was to determine if starch superplasticizers (SSPs) could be a suitable additive for geopolymers by carrying out basic investigations with respect to slump, hardening, compressive and flexural strength, shrinkage, and porosity. Four SSPs were synthesized, differing in charge polarity and specific charge density. Two conventional PCE superplasticizers, differing in terms of molecular structure, were also included in this study. The results revealed that SSPs improved the slump of a metakaolin-based geopolymer (MK-geopolymer) mortar while the PCE investigated showed no improvement. The impact of superplasticizers on early hardening (up to 72 h) was negligible. Less linear shrinkage over the course of 56 days was seen for all samples in comparison with the reference. Compressive strengths of SSP specimens tested after 7 and 28 days of curing were comparable to the reference, while PCE led to a decline. The SSPs had a small impact on porosity with a shift to the formation of more gel pores while PCE caused an increase in porosity. Throughout this research, SSPs were identified as promising superplasticizers for MK-geopolymer mortar and concrete.}, subject = {Geopolymere}, language = {en} } @article{SchirmerOsburg, author = {Schirmer, Ulrike and Osburg, Andrea}, title = {A new method for the quantification of adsorbed styrene acrylate copolymer particles on cementitious surfaces: a critical comparative study}, series = {SN Applied Sciences}, volume = {2020}, journal = {SN Applied Sciences}, number = {Volume 2, article 2061}, publisher = {Springer}, address = {Heidelberg}, doi = {10.1007/s42452-020-03825-5}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210804-44729}, pages = {1 -- 11}, abstract = {The amount of adsorbed styrene acrylate copolymer (SA) particles on cementitious surfaces at the early stage of hydration was quantitatively determined using three different methodological approaches: the depletion method, the visible spectrophotometry (VIS) and the thermo-gravimetry coupled with mass spectrometry (TG-MS). Considering the advantages and disadvantages of each method, including the respectively required sample preparation, the results for four polymer-modified cement pastes, varying in polymer content and cement fineness, were evaluated. To some extent, significant discrepancies in the adsorption degrees were observed. There is a tendency that significantly lower amounts of adsorbed polymers were identified using TG-MS compared to values determined with the depletion method. Spectrophotometrically generated values were ​​lying in between these extremes. This tendency was found for three of the four cement pastes examined and is originated in sample preparation and methodical limitations. The main influencing factor is the falsification of the polymer concentration in the liquid phase during centrifugation. Interactions in the interface between sediment and supernatant are the cause. The newly developed method, using TG-MS for the quantification of SA particles, proved to be suitable for dealing with these revealed issues. Here, instead of the fluid phase, the sediment is examined with regard to the polymer content, on which the influence of centrifugation is considerably lower.}, subject = {Zement}, language = {en} } @article{CappachionePartschefeldOsburgetal., author = {Cappachione, Clotilde and Partschefeld, Stephan and Osburg, Andrea and Gliubizzi, Rocco and Gaeta, Carmine}, title = {Modified Carboxymethylcellulose-Based Scaffolds as New Potential Ecofriendly Superplasticizers with a Retardant Effect for Mortar: From the Synthesis to the Application}, series = {Materials}, volume = {2021}, journal = {Materials}, number = {volume 14, issue 13, article 3569}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma14133569}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210804-44689}, pages = {1 -- 17}, abstract = {This article is focused on the research and development of new cellulose ether derivatives as innovative superplasticizers for mortar systems. Several synthetic strategies have been pursued to obtain new compounds to study their properties on cementitious systems as new bio-based additives. The new water-soluble admixtures were synthesized using a complex carboxymethylcellulose-based backbone that was first hydrolyzed and then sulfo-ethylated in the presence of sodium vinyl sulphonate. Starting with a complex biopolymer that is widely known as a thickening agent was very challenging. Only by varying the hydrolysis times and temperatures of the reactions was achieved the aimed goal. The obtained derivatives showed different molecular weight (Mw) and anionic charges on their backbones. An improvement in shear stress and dynamic viscosity values of CEM II 42.5R cement was observed with the samples obtained with a longer time of higher temperature hydrolysis and sulfo-ethylation. Investigations into the chemical nature of the pore solution, calorimetric studies and adsorption experiments clearly showed the ability of carboxymethyl cellulose superplasticizer (CMC SP) to interact with cement grains and influence hydration processes within a 48-h time window, causing a delay in hydration reactions in the samples. The fluidity of the cementitious matrices was ascertained through slump test and preliminary studies of mechanical and flexural strength of the hardened mortar formulated with the new ecological additives yielded values in terms of mechanical properties. Finally, the computed tomography (CT) images completed the investigation of the pore network structure of hardened specimens, highlighting their promising structure porosity.}, subject = {M{\"o}rtel}, language = {en} } @article{PartschefeldWiegandBellmannetal., author = {Partschefeld, Stephan and Wiegand, Torben and Bellmann, Frank and Osburg, Andrea}, title = {Formation of Geopolymers Using Sodium Silicate Solution and Aluminum Orthophosphate}, series = {Materials}, volume = {2020}, journal = {Materials}, number = {Volume 13, issue 18, article 4202}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma13184202}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210122-43378}, pages = {1 -- 16}, abstract = {This paper reports the formation and structure of fast setting geopolymers activated by using three sodium silicate solutions with different modules (1.6, 2.0 and 2.4) and a berlinite-type aluminum orthophosphate. By varying the concentration of the aluminum orthophosphate, different Si/Al-ratios were established (6, 3 and 2). Reaction kinetics of binders were determined by isothermal calorimetric measurements at 20 °C. X-ray diffraction analysis as well as nuclear magnetic resonance (NMR) measurements were performed on binders to determine differences in structure by varying the alkalinity of the sodium silicate solutions and the Si/Al-ratio. The calorimetric results indicated that the higher the alkalinity of the sodium silicate solution, the higher the solubility and degree of conversion of the aluminum orthophosphate. The results of X-ray diffraction and Rietveldt analysis, as well as the NMR measurements, confirmed the assumption of the calorimetric experiments that first the aluminum orthophosphate was dissolved and then a polycondensation to an amorphous aluminosilicate network occurred. The different amounts of amorphous phases formed as a function of the alkalinity of the sodium silicate solution, indicate that tetrahydroxoaluminate species were formed during the dissolution of the aluminum orthophosphate, which reduce the pH value. This led to no further dissolution of the aluminum orthophosphate, which remained unreacted.}, subject = {Geopolymere}, language = {en} } @article{SirtlHadlichKrausetal., author = {Sirtl, Christin and Hadlich, Christiane and Kraus, Matthias and Osburg, Andrea}, title = {Determination of Bonding Failures in Transparent Materials with Non-Destructive Methods - Evaluation of Climatically Stressed Glued and Laminated Glass Compounds}, series = {World Journal of Engineering and Technology}, volume = {2018}, journal = {World Journal of Engineering and Technology}, number = {Vol. 6, No 2}, doi = {10.4236/wjet.2018.62020}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20180606-37526}, pages = {315 -- 331}, abstract = {As part of an international research project - funded by the European Union - capillary glasses for facades are being developed exploiting storage energy by means of fluids flowing through the capillaries. To meet highest visual demands, acrylate adhesives and EVA films are tested as possible bonding materials for the glass setup. Especially non-destructive methods (visual analysis, analysis of birefringent properties and computed tomographic data) are applied to evaluate failure patterns as well as the long-term behavior considering climatic influences. The experimental investigations are presented after different loading periods, providing information of failure developments. In addition, detailed information and scientific findings on the application of computed tomographic analyses are presented.}, subject = {Klebtechnik}, language = {en} } @article{GoebelLahmerOsburg, author = {G{\"o}bel, Luise and Lahmer, Tom and Osburg, Andrea}, title = {Uncertainty analysis in multiscale modeling of concrete based on continuum micromechanics}, series = {European Journal of Mechanics-A/Solids}, journal = {European Journal of Mechanics-A/Solids}, abstract = {Uncertainty analysis in multiscale modeling of concrete based on continuum micromechanics}, subject = {Angewandte Mathematik}, language = {en} } @article{JentschKulleBodeetal., author = {Jentsch, Mark F. and Kulle, Christoph and Bode, Tobias and Pauer, Toni and Osburg, Andrea and Namgyel, Karma and Euthra, Karma and Dukjey, Jamyang and Tenzin, Karma}, title = {Field study of the building physics properties of common building types in the Inner Himalayan valleys of Bhutan}, series = {Energy for Sustainable Development 38}, journal = {Energy for Sustainable Development 38}, doi = {10.25643/bauhaus-universitaet.3139}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170419-31393}, pages = {48 -- 66}, abstract = {Traditionally, buildings in the Inner Himalayan valleys of Bhutan were constructed from rammed earth in the western regions and quarry stone in the central and eastern regions. Whilst basic architectural design elements have been retained, the construction methods have however changed over recent decades alongside expectations for indoor thermal comfort. Nevertheless, despite the need for space heating, thermal building performance remains largely unknown. Furthermore, no dedicated climate data is available for building performance assessments. This paper establishes such climatological information for the capital Thimphu and presents an investigation of building physics properties of traditional and contemporary building types. In a one month field study 10 buildings were surveyed, looking at building air tightness, indoor climate, wall U-values and water absorption of typical wall construction materials. The findings highlight comparably high wall U-values of 1.0 to 1.5 W/m²K for both current and historic constructions. Furthermore, air tightness tests show that, due to poorly sealed joints between construction elements, windows and doors, many buildings have high infiltration rates, reaching up to 5 air changes per hour. However, the results also indicate an indoor climate moderating effect of more traditional earth construction techniques. Based on these survey findings basic improvements are being suggested.}, subject = {Luftdichtheit}, language = {en} } @inproceedings{GoebelOsburgLahmer, author = {G{\"o}bel, Luise and Osburg, Andrea and Lahmer, Tom}, title = {STUDY OF ANALYTICAL MODELS OF THE MECHANICAL BEHAVIOR OF POLYMER-MODIFIED CONCRETE}, series = {Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar}, booktitle = {Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 20 - 22 2015, Bauhaus-University Weimar}, editor = {G{\"u}rlebeck, Klaus and Lahmer, Tom}, organization = {Bauhaus-Universit{\"a}t Weimar}, issn = {1611-4086}, doi = {10.25643/bauhaus-universitaet.2797}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170314-27973}, pages = {9}, abstract = {Polymer modification of mortar and concrete is a widely used technique in order to improve their durability properties. Hitherto, the main application fields of such materials are repair and restoration of buildings. However, due to the constant increment of service life requirements and the cost efficiency, polymer modified concrete (PCC) is also used for construction purposes. Therefore, there is a demand for studying the mechanical properties of PCC and entitative differences compared to conventional concrete (CC). It is significant to investigate whether all the assumed hypotheses and existing analytical formulations about CC are also valid for PCC. In the present study, analytical models available in the literature are evaluated. These models are used for estimating mechanical properties of concrete. The investigated property in this study is the modulus of elasticity, which is estimated with respect to the value of compressive strength. One existing database was extended and adapted for polymer-modified concrete mixtures along with their experimentally measured mechanical properties. Based on the indexed data a comparison between model predictions and experiments was conducted by calculation of forecast errors.}, subject = {Angewandte Informatik}, language = {en} }