TY - JOUR A1 - Wiegand, Torben A1 - Osburg, Andrea T1 - Synthesis, Curing and Thermal Behavior of Amine Hardeners from Potentially Renewable Sources JF - Polymers N2 - 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. KW - Epoxide KW - Epoxidharz KW - Polymere KW - epoxy KW - amine hardener KW - curing agent KW - bio-based KW - vanillin KW - OA-Publikationsfonds2023 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20230524-63745 UR - https://www.mdpi.com/2073-4360/15/4/990 VL - 2023 IS - volume 15, issue 4, article 990 SP - 1 EP - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - Tutal, Adrian A1 - Partschefeld, Stephan A1 - Schneider, Jens A1 - Osburg, Andrea T1 - Effects of Bio-Based Plasticizers, Made From Starch, on the Properties of Fresh and Hardened Metakaolin-Geopolymer Mortar: Basic Investigations JF - Clays and Clay Minerals N2 - 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. KW - Geopolymere KW - Metakaolin KW - Superplasticizer Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210804-44737 UR - https://link.springer.com/article/10.1007%2Fs42860-020-00084-8 VL - 2020 IS - volume 68, No. 5 SP - 413 EP - 427 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Sirtl, Christin A1 - Hadlich, Christiane A1 - Kraus, Matthias A1 - Osburg, Andrea T1 - Determination of Bonding Failures in Transparent Materials with Non-Destructive Methods – Evaluation of Climatically Stressed Glued and Laminated Glass Compounds JF - World Journal of Engineering and Technology N2 - 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. KW - Klebtechnik KW - Non-Destructive Testing KW - Bonding Methods KW - OA-Publikationsfonds2018 Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20180606-37526 UR - http://www.scirp.org/journal/PaperInformation.aspx?PaperID=84507 VL - 2018 IS - Vol. 6, No 2 SP - 315 EP - 331 ER - TY - JOUR A1 - Schirmer, Ulrike A1 - Osburg, Andrea T1 - A new method for the quantification of adsorbed styrene acrylate copolymer particles on cementitious surfaces: a critical comparative study JF - SN Applied Sciences N2 - 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. KW - Zement KW - Polymere KW - polymer adsorption KW - cement KW - visible spectrophotometry KW - depletion method KW - mass spectrometry Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210804-44729 UR - https://link.springer.com/article/10.1007/s42452-020-03825-5 VL - 2020 IS - Volume 2, article 2061 SP - 1 EP - 11 PB - Springer CY - Heidelberg ER - TY - CHAP A1 - Schirmer, Ulrike A1 - Kleiner, Florian A1 - Osburg, Andrea T1 - Objektive Oberflächenbewertung von (P)SCC-Sichtbeton mittels automatisierter Analyse von Bilddaten T2 - Tagung Bauchemie der GDCH-Fachgruppe Bauchemie, 30. September - 2. Oktober 2019 in Aachen N2 - Sichtbeton ist aufgrund seiner Vielfältigkeit in der Formgebung eines der am meisten verbreiteten Gestaltungsmittel der modernen Architektur und optimal für neue Bauweisen sowie steigende Anforderungen an das Erscheinungsbild öffentlicher Bauwerke geeignet. Die Herstellung qualitativ hochwertiger Sichtbetonoberflächen hängt 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 Einflüsse auf die Sichtbetonoberflächen eines polymermodifizierten selbstverdichtenden Betons (PSCC) im Vergleich zu einem herkömmlichen selbstverdichtenden Beton (SCC) untersucht. Im Rahmen dieser Arbeiten wurde eine Methode zur Beurteilung der Sichtbetonqualität entwickelt, mit welcher Ausschlusskriterien, wie maximale Porosität und Gleichmäßigkeit, objektiv und automatisiert bestimmt werden können. Veränderungen dieser Werte durch Witterungseinflüsse ließen zudem erste Rückschlüsse auf die Dauerhaftigkeit der Sichtbetonoberflächen zu. KW - Sichtbeton KW - Bildanalyse KW - Qualitätskontrolle KW - Sichtbeton KW - Oberflächenanalyse KW - Oberflächenporosität Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20211004-45104 SN - 978-3-947197-13-2 N1 - GDCh-Monographie ; Band 54 PB - Gesellschaft Deutscher Chemiker ER - TY - JOUR A1 - Partschefeld, Stephan A1 - Wiegand, Torben A1 - Bellmann, Frank A1 - Osburg, Andrea T1 - Formation of Geopolymers Using Sodium Silicate Solution and Aluminum Orthophosphate JF - Materials N2 - 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. KW - Geopolymere KW - geopolymer KW - berlinite KW - sodium silicate solution KW - alumosilicate KW - OA-Publikationsfonds2020 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210122-43378 UR - https://www.mdpi.com/1996-1944/13/18/4202 VL - 2020 IS - Volume 13, issue 18, article 4202 SP - 1 EP - 16 PB - MDPI CY - Basel ER - TY - JOUR A1 - Partschefeld, Stephan A1 - Tutal, Adrian A1 - Halmanseder, Thomas A1 - Schneider, Jens A1 - Osburg, Andrea T1 - Investigations on Stability of Polycarboxylate Superplasticizers in Alkaline Activators for Geopolymer Binders JF - Materials N2 - 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. KW - Geopolymere KW - Verflüssigung KW - metakaoline KW - superplasticizer KW - polycarboxylate ether KW - OA-Publikationsfonds2023 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20231026-64809 UR - https://www.mdpi.com/1996-1944/16/15/5369 VL - 2023 IS - Volume 16, issue 15, article 5369 SP - 1 EP - 14 PB - MDPI CY - Basel ER - TY - JOUR A1 - Motra, Hem Bahadur A1 - Hildebrand, Jörg A1 - Dimmig-Osburg, Andrea T1 - Assessment of strain measurement techniques to characterise mechanical properties of structural steel JF - Engineering Science and Technology, an International Journal N2 - Strain measurement is important in mechanical testing. A wide variety of techniques exists for measuring strain in the tensile test; namely the strain gauge, extensometer, stress and strain determined by machine crosshead motion, Geometric Moire technique, optical strain measurement techniques and others. Each technique has its own advantages and disadvantages. The purpose of this study is to quantitatively compare the strain measurement techniques. To carry out the tensile test experiments for S 235, sixty samples were cut from the web of the I-profile in longitudinal and transverse directions in four different dimensions. The geometry of samples are analysed by 3D scanner and vernier caliper. In addition, the strain values were determined by using strain gauge, extensometer and machine crosshead motion. Three techniques of strain measurement are compared in quantitative manner based on the calculation of mechanical properties (modulus of elasticity, yield strength, tensile strength, percentage elongation at maximum force) of structural steel. A statistical information was used for evaluating the results. It is seen that the extensometer and strain gauge provided reliable data, however the extensometer offers several advantages over the strain gauge and crosshead motion for testing structural steel in tension. Furthermore, estimation of measurement uncertainty is presented for the basic material parameters extracted through strain measurement. KW - Baustahl KW - Werkstoffprüfung KW - Zugversuch KW - Affecting factors; Measurement uncertainty; Materials testing; Quantitative comparison; Strain comparison; Tensile test Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170425-31540 SP - 260 EP - 269 ER - TY - CHAP A1 - Motra, Hem Bahadur A1 - Dimmig-Osburg, Andrea A1 - Hildebrand, Jörg ED - Gürlebeck, Klaus ED - Lahmer, Tom ED - Werner, Frank T1 - UNCERTAINTY QUANTIFICATION IN CYCLIC CREEP PREDICTION OF CONCRETE T2 - Digital Proceedings, International Conference on the Applications of Computer Science and Mathematics in Architecture and Civil Engineering : July 04 - 06 2012, Bauhaus-University Weimar N2 - This paper presents a methodology for uncertainty quantification in cyclic creep analysis. Several models- , namely BP model, Whaley and Neville model, modified MC90 for cyclic loading and modified Hyperbolic function for cyclic loading are used for uncertainty quantification. Three types of uncertainty are included in Uncertainty Quantification (UQ): (i) natural variability in loading and materials properties; (ii) data uncertainty due to measurement errors; and (iii) modelling uncertainty and errors during cyclic creep analysis. Due to the consideration of all type of uncertainties, a measure for the total variation of the model response is achieved. The study finds that the BP, modified Hyperbolic and modified MC90 are best performing models for cyclic creep prediction in that order. Further, global Sensitivity Analysis (SA) considering the uncorrelated and correlated parameters is used to quantify the contribution of each source of uncertainty to the overall prediction uncertainty and to identifying the important parameters. The error in determining the input quantities and model itself can produce significant changes in creep prediction values. The variability influence of input random quantities on the cyclic creep was studied by means of the stochastic uncertainty and sensitivity analysis namely the Gartner et al. method and Saltelli et al. method. All input imperfections were considered to be random quantities. The Latin Hypercube Sampling (LHS) numerical simulation method (Monte Carlo type method) was used. It has been found by the stochastic sensitivity analysis that the cyclic creep deformation variability is most sensitive to the Elastic modulus of concrete, compressive strength, mean stress, cyclic stress amplitude, number of cycle, in that order. KW - Angewandte Informatik KW - Angewandte Mathematik KW - Computerunterstütztes Verfahren Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170314-27803 UR - http://euklid.bauing.uni-weimar.de/ikm2012 SN - 1611-4086 ER - TY - CHAP A1 - Kleiner, Florian A1 - Wiegand, Torben A1 - Osburg, Andrea T1 - Eigenschaftsentwicklung epoxidharzmodifizierter Mörtel auf Zementbasis bei unterschiedlichen klimatischen Bedingungen T2 - Tagung Bauchemie der GDCh-Fachgruppe Bauchemie, 18.-20. September 2017 in Weimar N2 - Zur Erstellung von dekorativen Plastiken sollten Mörtel entwickelt werden, die eine hohe Biegezugfestigkeit aufweisen und eine breite Palette von Konsistenzen für verschiedene Anwendungsarten, wie Gießen, Spachteln oder Stampfen abdecken. Als Basis für die Rezepturen wurde ein niedrigviskoses Epoxidharzsystem gewählt, dessen Aminhärter einen Wasseranteil von 44 % beinhaltet. Dies ermöglichte es, durch Wasserzugabe verschiedene Viskositäten einzustellen. Um dieses Wasser in massiveren Bauteilen zu binden, wurde neben Sand auch Zement als Füllstoff eingesetzt. Die erstellten Rezepturen zeigten nach 56 Tagen hohe Druckfestigkeiten von über 50 N/mm². Mit zunehmendem Epoxidharzgehalt ergaben sich zwar steigende Biegezugfestigkeiten, jedoch unter Laborlagerung auch größere Längenänderungen. Diese konnten durch den Einsatz eines PCE-Fließmittels, PVA-Kurzfasern und einer optimierten Sieblinie verringert werden. Das Fließmittel verlängerte die Erhärtungszeiten jedoch auf bis zu 1,5 Tage. Zur Ermittlung der Dauerhaftigkeit des Materials wurde es für drei Wochen Temperaturen von -20 bis +60 °C, einer künstlichen Sonnenbestrahlung sowie künstlicher Beregnung ausgesetzt. Im Vergleich zur Laborlagerung ergab sich bei steigendem Epoxidharzanteil ein geringerer Schwund, während die Biegezugfestigkeit der Probeköper nur geringfügig abnahm. Rasterelektronenmikroskopische Untersuchungen zeigten, dass auch bei geringeren Epoxidharzzusätzen Störungen der Zementhydratation auftraten. Weiterhin zeigen sich bei geringen Epoxidharzzusätzen in der Matrix kugelförmige Einschlüsse, die von dispergierten Epoxidharzpartikeln stammen. KW - Bauchemie KW - Mörtel KW - Epoxidharz KW - Dauerhaftigkeit Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20211004-45067 SN - 978-3-947197-02-6 PB - Gesellschaft Deutscher Chemiker ER -