In situ x-ray diffraction at high temperatures: Formation of Ca2_{2}SiO4_{4} and ternesite in recycled autoclaved aerated concrete

This study provides an insight into possible recycling processes for autoclaved aerated concrete (AAC) at low temperatures (<1000 °C). Belite binders were synthesized from wastes of AAC by the addition of CaCO$_{3}$ and adaption of the molar CaO/SiO$_{2}$ (C/S ratio) in the range of 2 to 2.5. An in situ XRD study performed during heating up to 1000 °C and subsequent quenching to room temperature evidenced the formation of ternesite besides C$_{2}$S in sulfate-containing systems. Several factors influencing the reaction kinetics and the evolution of the phase composition were investigated thoroughly. Increased sulfate content and dwelling time during heating increase the ternesite content and promote the formation of highly crystalline α’H-C$_{2}$S. The C/S-ratio of the starting materials has to be adjusted to the sulfate content in order to prevent the formation of ternesite at the expense of C$_{2}$S. Ternesite remains stable during quenching to room temperature or even increases in amount, except in cases of very low cooling rates or high residual quartz contents (C/S-ratio ≤ 2). Temperature and range of α’H-C$_{2}$S to β-C$_{2}$S phase transition on quenching strongly depend on the cooling rate. The onset temperature for β-C$_{2}$S formation varies between 540 °C (slow quench) and 450 °C (fast quench). Thermal expansion coefficients of ternesite are calculated showing similarity with C$_{2}$S. The incorporation of CaSO$_{4}$ modules in the structure switches the direction of maximum compression

Evidenzbasierte Diagnostik phonologischer Störungen - Entwicklung und Evaluation eines Sprachanalyseverfahrens auf der Basis nichtlinearer phonologischer Theorien

Forderungen nach einer Qualitätssicherung in der sprachtherapeutischen Diagnostik werden durch die fortlaufende Umstrukturierung des deutschen Gesundheitswesens und der Adaption des Konzepts der evidenzbasierten Praxis zunehmend dringlicher (Schmacke, 2000; Beushausen 2009). Als grundlegende Voraussetzung für eine qualitätssichernde Diagnostik müssen Therapeuten Verfahren zur Verfügung stehen, deren zugrunde liegende Theorien der besten wissenschaftlichen Evidenz zur Beantwortung der jeweiligen diagnostischen Fragestellung entsprechen und die empirisch auf die Erfüllung von Gütekriterien überprüft wurden (Klee, 2008). Nicht nur durch eine unzureichende theoretische Fundierung, sondern auch angesichts einer Ermangelung adäquater Gütekriterien, die an die Ziele und Methoden qualitativer Sprachanaylseverfahren angepasst sind, vermögen bisherige Verfahren zur Diagnostik phonologischer Störungen die Erfüllung dieser Anforderungen nicht zu leisten. Das im Rahmen der vorliegenden Dissertation vorgestellte Sprachanalyseverfahren NILPOD zielt (1.) auf die differenzierte Rekonstruktion des zugrunde liegenden, kindspezifischen phonologischen Systems, (2.) der Identifizierung der im Vergleich zum phonologischen System der Zielsprache noch nicht erworbenen phonologischen Strukturen sowie (3.) der Ableitung von Zielen zur individuellen und störungsspezifischen Therapieplanung ab (Romonath, 2007). Das Verfahren wurde unter Bezugnahme auf nichtlineare phonologische Theorien entwickelt, die der derzeit besten Evidenz für eine adäquate Beschreibung des phonologischen Systems der Zielsprache und der Beschreibung normaler und gestörter phonologischer Entwicklungsverläufe entsprechen (Bernhardt & Stemberger, 1998). Darüber hinaus wurden bei der Entwicklung Gütekriterien der quantitativen und qualitativen Forschung explizit berücksichtigt. Von den als relevant identifizierten Kriterien wurden die Kriterien Auswertungsobjektivität, Interpretationsobjektivität, Ökonomie und Nützlichkeit im Rahmen einer formativen Evaluationsstudie überprüft. Ausgangspunkt der Studie bildete eine dreitägige Schulung an der 60 Sprachtherapeuten und Logopäden teilnahmen, denen theoretische Grundlagen der nichtlinearen Phonologie und die praktische Anwendung von NILPOD vermittelt wurden. Im Anschluss an die Schulung bekamen die Therapeuten transkribierte Datensätze von vier phonologisch auffälligen Kindern mit der Aufgabe diese mit Hilfe von NILPOD auszuwerten und hinsichtlich der Ableitung von Therapiezielen zu interpretieren. Darüber hinaus wurde ihnen ein Evaluationsbogen ausgehändigt, in dem sie Fragen zu den Nebengütekriterien Ökonomie und Nützlichkeit beantworten sollten. Durch die Ergebnisse der Studie bestätigt werden konnte die Erfüllung der Kriterien Auswertungsobjektivität und Nützlichkeit, während die Kriterien Interpretationsobjektivität und Ökonomie noch Raum für eine Optimierung lassen. Durch diesen kontrollierten Entwicklungsprozess hebt sich das Sprachanalyseverfahren NILPOD deutlich von bisherigen Verfahren ab und kann langfristig einen wesentlichen Beitrag zur Qualitätsverbesserung in der sprachtherapeutischen Intervention bei phonologischen Störungen leisten. Bernhardt, B. M. & Stemberger, J. P. (1998). Handbook of phonological development: From the perspective of a constraint-based nonlinear phonology San Diego, CA: Academic Press. Beushausen, U. (2005). Evidenz-basierte Praxis. Mythos und Realität. Forum Logopädie, 19, 7-12. Klee, T. (2008). Considerations for appraising diagnostic studies of communication disorders. Evidence-Based Communication Assessment and Intervention, 2, 34-45. Romonath, R. (2007). Diagnostik von phonetischen und phonologischen Störungen bei SSES: Theoretische Grundlagen, Vorgehensweisen und Perspektiven. In: Schöler, H. & Welling, A. (Hg.). Sonderpädagogik der Sprache (S. 550-573) Göttingen: Hogrefe. Schmacke, N. (2000). Qualitätssicherung in der Medizin: Hintergründe einer aktuellen gesundheitspolitischen Diskussion. In: G. Homburg, C. Iven & V. Maihack (Hg.). Qualitätsmanagement in der Sprachtherapie. Kontrollmechanismen oder Kompetenzgewinn? (S. 13-26). Köln: ProLog Verlag

Zero emission circular concrete

The project Zero Emission Circular Concrete develops a CO2-neutral, high-quality, and resource-efficient concrete cycle starting with end-of-life concrete. A cement clinker with a reduced CO2 footprint is processed from waste concrete fines at a strongly reduced temperature of approximately 1000°C. The main clinker mineral is belite, Ca2SiO4. The residual CO2 is released in concentrated form and used for the technical carbonation of either waste concrete fines as supplementary cementitious material or of coarse crushed waste concrete. The coarse fraction is treated in a new process based on a pressurized autoclave, where hardening by carbonation improves the properties of the recycled aggregate. Both carbonation options are investigated on a laboratory scale. Recycling cement is developed from belite cement clinker, Portland cement clinker, and other substitutes in a joint project with the industry. A 30% substitution rate of Portland cement clinker compared to European cement standards is targeted. Subsequently, formulations for recycling concrete will be developed from recycled cement and recycled aggregate. The processing of concrete products and precast concrete elements will be tested in plant trials. A pilot plant for belite cement clinker is currently under construction to bring its technology readiness level to four

Wertigkeit von Eisenstoffwechselparametern in der Diagnostik der eisendefizitären Erythropoese bei chronisch nierentransplantierten Patienten

Der Eisenhaushalt spielt eine entscheidende Rolle in der Therapie der renalen Anämie unter einer chronischen Erythropoetintherapie. Patienten nach erfolgreicher Nierentransplantation zeigen neben der renalen Anämie auch vermehrt chronisch entzündliche Veränderungen. Um die Wertigkeit der einzelnen Parameter bei nierentransplantierten Patienten zu bestimmen wurde eine Gruppe von 14 Patienten mit vermindertem Hämoglobingehalt und reduziertem Ferritin oder verminderter Transferrinsättigung mit intravenösem Eisen behandelt. Gemessen wurden dabei: Ferritin, Transferrinsättigung, Zink- Protoporhyrin, der Prozentsatz hypochromer Erythrozyten sowie der lösliche Transferrin - Rezeptor. Von den 14 Patienten mit vermutetem Eisenmangel zeigten 64% einen signifikanten Anstieg der Hämoglobinkonzentration. Die höchste Sensitivität und Spezifität für ein Ansprechen auf eine intravenöse Eisentherapie ergab sich für die Kombination eines Hämoglobin Wertes unter 10 g/dl vor Therapie und eine Transferrinsättigung unter 15 %

Belite cement clinker from autoclaved aerated concrete waste fines with high sulfate content

The processing of belite cement clinker in a rotary kiln at about 1000°C in a CO2 atmosphere is a new recycling option for Autoclaved Aerated Concrete (AAC) waste that otherwise must be landfilled. Waste fine fractions from a sorting facility enriched in sulfate due to intermixing with waste plaster have been processed. During clinkering the cement clinker phase belite (Ca2SiO4) besides technical ellestadite, (Ca10(SiO4)3(SO4)3Cl2), or ternesite, (Ca5(SiO4)2SO4), are formed, depending on the addition of flux minerals. However, not all phases of the novel clinker react hydraulically. Whereas ternesite reacts with water, ellestadite forms complex solid solution series (Ca/Pb, SO4/PO4), which may be used as an insoluble reservoir mineral for undesirable constituents, such as phosphates and chlorides. The produced clinker has been successfully used to partially substitute OPC in AAC production in technical trials. Waste quantities and landfill costs are minimized, while at the same time, CO2 emissions and the primary resource consumption of AAC production are reduced. Joint work with industrial companies is underway to increase technology readiness. Particularly large reduction effects on CO2 emissions can be achieved through electrical heating of the rotary kiln

Belite cement clinker from autoclaved aerated concrete waste – A contribution towards CO₂-reduced circular building materials

The processing of belite cement clinker in a rotary kiln at about 1000oC is a new recycling option for autoclaved aerated concrete (AAC) waste that otherwise must be landfilled. The clinker produced can partially substitute ordinary portland cement (OPC) in AAC production. Waste quantities and landfill costs are minimized, while at the same time CO2 emissions and the primary resource consumption of AAC production are reduced. The technology is currently under development. New analytical possibilities and modeling have made it possible to optimize the process conditions to such an extent that the use of belite cement clinker in aerated concrete production has already been technically tested. Particularly large effects on CO2 emissions can be achieved through the electrical heating of the rotary kiln and the coupled sequestration of the released CO2 in other secondary products such as recycled aggregate for concrete production from waste concrete. Comparable concepts for the AAC cycle are currently being worked on together with the industry partner Xella. Although decentralized plant concepts would be useful in order to minimize transportation, small plants are currently not economical according to initial estimates. In the long term, emission-free product cycles are aimed at

Chlorellestadite (Synth): Formation, Structure, and Carbonate Substitution during Synthesis of Belite Clinker from Wastes in the Presence of CaCl2_2 and CO2_2

The synthesis of low-temperature belite (C$_2$S) clinker from wastes of autoclaved aerated concrete and limestone was studied in the presence of CaCl$_2$ as a mineralizing agent. Synthetic chlorellestadite (SCE; Ca$_{10}$(SiO$_4$)$_3$(SO$_4$)$_3$Cl$_2$) forms in experiments at temperatures between 700 and 1200 °C. Samples were investigated by X-ray diffraction and Raman spectroscopy. In general, the amount of SCE depends mainly on the sulfate content and to a lesser extent on the synthesis temperature. At lower temperatures of formation, a non-stoichiometric SCE seems to crystallize in a monoclinic symmetry similar to hydroxylellestadite. Rietveld refinements revealed the presence of chlorine and calcium vacancies. Raman spectroscopy proved the partial substitution of sulfate by CO$_3$$^{2−}$ groups in ellestadites formed at 800 °C and 900 °C in air. Incorporation of CO$_3$ results in a shorter unit cell parameters and smaller cell volume similar to CO$_{3−}$apatite. At low temperatures, SCE coexists with spurrite intermixed on a very fine nm scale. At temperatures above 900 °C in air, ellestadite is carbonate-free and above 1000 °C chlorine loss starts in all samples

Accelerated carbonation of hardened cement paste: Quantification of calcium carbonate via ATR infrared spectroscopy

In context of carbon capture and storage in cement and concrete industry, there is a strong demand for fast, reliable, and low-cost CO2 quantification methods. Attenuated total reflection infrared spectroscopy (ATR-IR) in conjunction with multivariate calibration via partial-least-squares regression was applied to quantify CaCO3 in carbonated hardened Portland cement pastes, as this method shows great potential in the field of process control. Thermogravimetric analysis coupled with infrared spectrometry for the detection of the evolving gases was used as a reference for quantification. Three methods for the quantitative analysis with different partial-least-squares parameters were developed on a series of ground physicalmixtures of slightly carbonated and highly carbonated hydrated cement pastes that had absorbed up to 77% of the theoretical capacity for CO2. Additional samples for optimization and validation of the method were prepared by accelerated carbonation of cylindrical slices of hardened cement paste as a function of exposure time. In these experiments, the major CO2 uptake occurs in the first 60 min until the formation of CaCO3 layers limits the diffusion of CO2 and Ca2+ ions. The developed partial-least-squares models provided low estimation errors of max. 1.5 wt% and high correlation coefficients above 99.5%. The validation covers a concentration range of 20–48 wt% of CaCO3. Limitations of the method are discussed

CaCl2 as a Mineralizing Agent in Low-Temperature Recycling of Autoclaved Aerated Concrete: Cl-Immobilization by Formation of Chlorellestadite

The suitability of CaCl2 as a mineralizing agent in the synthesis of a low-temperature C2S-cement clinker from wastes of autoclaved aerated concrete was investigated. As chlorellestadite is a potential host mineral for the immobilization of chlorine, the formation conditions for the highest joint content of chlorellestadite and C2S were studied in samples with different sulfate contents. Oven experiments were conducted at temperatures between 700 and 1200 °C. The samples were analyzed by X-ray diffraction in combination with chemical and thermal analysis and Raman spectroscopy. Calculation of the yield of C2S and ellestadite for all samples proves the optimum temperature range for the C2S-ellestadite clinker from 950 to 1000 °C. At lower temperatures, the formation of a carbonate-rich halogenide melt promotes the crystallization of a significant amount of spurrite at the expense of C2S. Ellestadite formation mainly depends on the sulfate content and to a lesser extent on the synthesis temperature. However, at higher temperatures, with ternesite another sulfate coexists in sulfate-rich samples at the expense of ellestadite. In addition, distinct evidence for non-stoichiometry and carbonate substitution in the structure of low-temperature ellestadite was found. Low sulfate content leads to the crystallization of Ca10[Si2O7]3Cl2 at higher temperatures. In all samples treated at temperatures above 1000 °C chlorine loss starts. Its extent decreases with increasing sulfate content

Praxishandbuch Online-Fundraising

Die Tage der Spendenbüchsen sind gezählt. Immer mehr Vereine, soziale Initiativen, Projekte und Stiftungen möchten nicht mehr (nur) auf der Straße oder via Brief, sondern kostensparend und effektiv im Internet Spenden sammeln und Unterstützer mobilisieren. In diesem Buch lernen Sie, wie das geht. Anhand vieler Praxisbeispiele werden die Grundlagen für erfolgreiches Online-Fundraising erläutert: von der nutzerfreundlichen Website-Gestaltung über effizientes Social-Media-Management bis hin zur Planung und Evaluation von Fundraising-Kampagnen