TY - JOUR A1 - Stroh, Julia A1 - Schlegel, Moritz-Caspar A1 - Schmidt, Wolfram A1 - Nguyen, Thi Yen A1 - Meng, Birgit A1 - Emmerling, Franziska T1 - Time-resolved in situ investigation of Portland cement hydration influenced by chemical admixtures N2 - Numerous admixtures are used in the building practice to customize the properties of the cement paste during application. The influences of admixtures on the course of cement hydration and formation of hydrate phases have to be considered. Polycarboxylate ether (PCE) based polymeric superplasticizers (SPs) are known to retard the setting of the cement paste. The extent of the retardation differs depending on the molecular structure of the SP. Additionally, the presence of a stabilizing agent (SA) in the cement paste has a retarding side effect on the setting. The initial cement hydration processes and the detailed mechanisms of the retardation influenced by PCEs, as well as their interactions with particular SAs, are insufficiently understood. Up to now, only the results of phenomenological studies were taken into account to describe this retardation process. A detailed structure analysis monitoring the change of the phase composition during the hydration was never applied. Both SP and SA affect the adsorption of the sulphate ions on the clinker particles, causing changes in the formation of ettringite during the initial hydration, and are therefore a crucial part of the setting process itself. Here, the initial hydration of cement influenced by the interaction of SP and SA was monitored in situ by synchrotron X-ray diffraction. The high time resolution of the measurements allowed a continuous detection of the hydrates formed. The hydration was followed from the starting point of water addition and for couple of hours afterwards. The hydration of the levitated cement pellets containing starch as SA was initialized by adding aqueous solutions of different commercial SPs. Changes in the ettringite formation were detected in comparison to the reference hydration of pure cement. KW - Synchrotron KW - Portland cement Initial hydration KW - Superplasticizer KW - Stabilizer KW - XRD PY - 2016 U6 - https://doi.org/http://dx.doi.org/10.1016/j.conbuildmat.2015.12.097 IS - 106 SP - 18 EP - 26 PB - Elsevier AN - OPUS4-35467 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nguyen, Thi Yen A1 - Bernardes, C. A1 - Minas da Piedade, M. E. A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Desolvation of indometacin solvates characterized structurally and kinetically N2 - The structure of indometacin solvates and the desolvation process of these compounds are investigated by synchrotron X-ray radiation, Raman spectroscopy and thermal analysis. T2 - Annual CM1402 crystallize COST meeting CY - Coimbra, Portugal DA - 06.04.2016 KW - Crystallization KW - In situ analysis KW - Indometacin KW - Active pharmaceutical ingredient (API) PY - 2016 AN - OPUS4-35872 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nguyen, Thi Yen A1 - Bernardes, C. A1 - Minas da Piedade, M. E. A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Direct evidence of polyamorphism in paracetamol N2 - While polymorphism is a common phenomenon in the crystallization processes of organic compounds, polyamorphism has gained importance only recently. Using sophisticated sample environments and applying in situ scattering methods and vibrational spectroscopy, the complete crystallization process of organic compounds from solution can be traced and characterized. Diffuse scattering from amorphous intermediates can be investigated by analyzing the atomic pair Distribution function (PDF) to gain further insights into molecular pre-orientation. The crystallization behavior of Paracetamol was studied exemplarily under defined, surface-free conditions. Based on the choice of the solvent, the formation of different polymorphs is promoted. The thermodynamically stable form I and the metastable orthorhombic form II could be isolated in pure form directly from solution. For both polymorphs, the crystallization from solution proceeds via a distinct amorphous precursor phase. PDF analyses of these different amorphous states indicate a specific pre-orientation of the analyte molecules introduced by the solvent. The resulting crystalline polymorph is already imprinted in these proto-crystalline precursors. Direct experimental evidence for the polyamorphism of paracetamol is provided. T2 - Annual CM1402 crystallize COST meeting CY - Coimbra, Portugal DA - 06.04.2016 KW - Paracetamol KW - Crystallization KW - In situ analysis KW - Active pharmaceutical ingredient (API) PY - 2016 AN - OPUS4-35873 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -