TY - JOUR A1 - Kleiner, Florian A1 - Rößler, Christiane A1 - Vogt, Franziska A1 - Osburg, Andrea A1 - Ludwig, Horst-Michael T1 - Reconstruction of calcium silicate hydrates using multiple 2D and 3D imaging techniques: Light microscopy, μ-CT, SEM, FIB-nT combined with EDX JF - Journal of Microscopy N2 - 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. KW - Zementklinker KW - Bildsegmentierung KW - Rasterelektronenmikroskopie KW - Computertomographie KW - tomography KW - focussed ion beam KW - cement microstructure KW - micro-CT Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20220106-45458 UR - https://onlinelibrary.wiley.com/doi/10.1111/jmi.13081 VL - 2021 SP - 1 EP - 6 PB - John Wiley & Sons Ltd CY - Oxford ER - TY - JOUR A1 - Cappachione, Clotilde A1 - Partschefeld, Stephan A1 - Osburg, Andrea A1 - Gliubizzi, Rocco A1 - Gaeta, Carmine T1 - Modified Carboxymethylcellulose-Based Scaffolds as New Potential Ecofriendly Superplasticizers with a Retardant Effect for Mortar: From the Synthesis to the Application JF - Materials N2 - 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. KW - Mörtel KW - Verflüssigung KW - superplasticizers KW - carboxymethylcellulose KW - mortar KW - OA-Publikationsfonds2021 Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20210804-44689 UR - https://www.mdpi.com/1996-1944/14/13/3569 VL - 2021 IS - volume 14, issue 13, article 3569 SP - 1 EP - 17 PB - MDPI CY - Basel 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 - 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 - 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 - 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 -