Macroporous ceramic materials have found widespread technological application ranging from particulate filters in diesel engines, tissue engineering scaffolds, and as support materials in carbon capture processes. This thesis demonstrates how the pore space of macroporous alumina can be manipulated, analysed in three-dimensions (3D) using visualisation techniques, and functionalised with a CO2-adsorbing material. A novel method was developed to produce macroporous alumina materials: by combining sacrificial templating with thermally expandable polymeric microspheres and gel-casting of an alumina suspension. This method offers a versatile production of macroporous ceramics in which the level of porosity and the pore size distribution can easily be altered by varying the amount and type of spheres. The permeability to fluid flow could be regulated by controlling the connectivity of the pore space and the size of the smallest constrictions between the pores. Sacrificial templating with particle-coated expandable spheres significantly increased the fraction of isolated pore clusters and reduced both the sizes and the numbers of connections between neighbouring pores, compared to templating with un-coated spheres. The macroporous alumina materials were characterised with X-ray micro-computed tomography (μ-CT). The 3D data-sets obtained by X-ray μ-CT were used to calculate the spatial variation in porosity, the throat and pore size distributions and to calculate the permeability to fluid flow. The throat and pore size distributions were also able to be accurately quantified in only one extrusion and intrusion cycle with water-based porosimetry; a relatively novel and simple characterisation technique. The pore walls of the macroporous alumina materials were also coated with zeolite films by a colloidal processing technique. The CO2-uptake of the coated alumina materials and of hierarchically porous monoliths of zeolites was evaluated and compared. / As the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Accepted. Paper 5: Manuscript. Paper 6: Submitted.

A expansão rápida da maxila assistida cirurgicamente (ERMAC) é o procedimento de eleição para o tratamento da deficiência transversa de maxila em pacientes esqueleticamente maduros. Controvérsias em relação ao procedimento ainda persistem principalmente relacionadas aos métodos de avaliação, técnica cirúrgica utilizada, morbidade, eficácia clínica e estabilidade de resultados. A utilização da tomografia computadorizada para a avaliação da eficiência da ERMAC é uma opção atual e ainda pouco divulgada. Consequentemente, os parâmetros anatômicos para a utilização deste método ainda não foram totalmente estabelecidos. Os objetivos do presente estudo foram avaliar a confiabilidade da metodologia proposta e as alterações esqueléticas maxilares decorrentes da ERMAC com a utilização do método de avaliação por tomografia computadorizada. No período de junho de 2004 a maio de 2005, 15 pacientes, sendo 10 do sexo feminino, foram submetidos a ERMAC. A técnica cirúrgica utilizada constou de osteotomia maxilar do tipo Le Fort I, sem osteotomia da sutura ptérigo-maxilar, associada a osteotomia sagital mediana do palato. O aparelho expansor utilizado foi do tipo Hyrax. Os pacientes foram submetidos a exames de tomografia computadorizada, em tomógrafos de múltiplos detectores, no pré-operatório e após 6 meses, utilizando-se metodologia idealizada para a avaliação específica deste procedimento cirúrgico. Para a determinação do padrão das alterações transversais e ântero-posteriores, medidas lineares e angulares foram realizadas diretamente na estação de trabalho dos aparelhos de tomografia. Através de imagens obtidas nas aquisições tomográficas axiais e em reconstruções coronais, as regiões anterior, média e posterior da maxila foram avaliadas separadamente. A área de secção transversa da maxila foi também calculada. Após a avaliação dos resultados observou-se que a confiabilidade do método foi estatisticamente comprovada. Um significativo aumento da área de secção transversa da maxila foi observado (p<0.05). Entretanto, o padrão de expansão transversa não se mostrou uniforme. O aumento das dimensões transversas nas regiões anterior e média foi estatisticamente comprovado. Não foi observada expansão transversa significativa na região posterior da maxila. Ao se avaliar a relação entre a abertura do parafuso expansor e a efetiva expansão esquelética da maxila, observou-se que esta foi menor que a abertura do parafuso, em termos absolutos. O aumento transverso relativo à expansão do parafuso foi estatisticamente maior nas regiões anterior e média da maxila do que em sua região posterior. Em conclusão, a avaliação por tomografia computadorizada para a análise das alterações esqueléticas da região maxilar, em pacientes submetidos à ERMAC é metodologia confiável e reprodutível. A expansão transversa da maxila decorrente do procedimento de ERMAC utilizado no presente estudo acarretou uma expansão não uniforme da maxila, com predomínio da expansão transversa nas regiões anterior e média. / Surgically assisted rapid palatal expansion is the procedure of choice for treating transverse maxillary deficiency in mature patients. Some controversies regarding surgically assisted rapid palatal expansion remain, mainly concerning technical aspects such as type and location of osteotomy sites, as well as surgical morbidity, clinical efficiency, and stability. The evaluation of transverse expansion is still a theme of discussion. On conventional anteroposterior radiographs, anatomical structures are superimposed, resulting in a high number of image artifacts, as well as hindering the tracing and evaluation. The use of computed tomography as a method of evaluating the efficiency of this procedure has not been widely reported. Consequently, few landmarks for use in evaluating maxillary expansion have been defined. The goals of the present study were to define parameters to assess skeletal changes after surgically assisted palatal expansion, to evaluate the reliability of the proposed method and to use computed tomography to assess those parameters. From June of 2004 to May of 2005, 15 patients underwent surgically assisted rapid palatal expansion (a modified Le Fort I maxillary osteotomy without pterygomaxillary separation, together with a sagital palatal osteotomy) according to a defined protocol, using a Hyrax appliance. To determine the pattern of transversal and anteroposterior expansion, linear and angular measurements were performed on multislice computed tomography, using computed software directly on the workstation. The anterior, intermediate and posterior portions of the maxilla were evaluated separately, using a specific method, in axial acquisition and coronal reconstructed views. The cross-sectional area of the maxilla was calculated to obtain general information about maxillary expansion. The reliability of the method was statistically confirmed. Significant maxillary overall expansion was observed. However, different patterns of expansion were seen in the three regions analyzed. In the anterior and intermediate portions of the maxilla, the increase in maxillary width was significantly greater than that observed in the posterior portion. The opening of the jackscrew was greater than skeletal expansion. Comparing jackscrew opening and transverse expansion, the same pattern of asymmetric expansion was verified. No change was observed in anteroposterior dimensions. The method of computed tomography evaluation is a useful tool for evaluation of surgically assisted rapid palatal expansion changes. The accurate evaluation of the postoperative changes was heavily dependent upon images acquired through computed tomography. An overall maxillary expansion was confirmed. However, transverse expansion of the maxilla achieved through surgically assisted rapid palatal expansion without pterygoid plate separation was less than uniform.

Introdução: O aumento alarmante da obesidade em todo mundo é um fator independente para o aumento da prevalência de doenças crônicas, como diabetes, hipertensão arterial e doença hepática gordurosa não alcoólica (DHGNA). A DHGNA engloba um amplo espectro de doença desde esteatose simples sem sinais inflamatórios, evoluindo para esteatohepatite (ENA) e até cirrose. Por ser uma patologia multifatorial sua patogênese e terapêutica ainda apresentam pontos obscuros. A resistência à insulina é um dos fatores que já foram determinados como importantes na fisiopatogênese da DHGNA e, está diretamente relacionado ao estilo de vida e hábitos alimentares. Objetivo: Avaliar a correlação entre a presença da gordura visceral e subcutânea à resistência insulínica, síndrome metabólica, medidas antropométricas e hábitos alimentares em pacientes portadores DHGNA. Resultados: Sessenta por cento dos pacientes com DHGNA apresentavam Síndrome Plurimetabólica de acordo com os critérios do ATP III. Dentre os critérios mais prevalentes da síndrome metabólica, níveis baixos HDL e circunferência de cintura (CC) aumentada ocorreram em 56%. Ao dividirmos os pacientes em grupos, os critérios se modificaram. Nos pacientes portadores de esteatose simples, o critério mais prevalente foi CC 77%. Já naqueles com ENA o aumento do nível de triglicérides ocorreu em 68% dos pacientes, sendo o de maior prevalência. As correlações entre CT e IMC (p=0,001), CC (p=0,003) e percentual de massa gorda (p=0,031), apresentam significância estatística negativa entre os pacientes com DHGNA. Não houve significância estatística entre CT e HOMA, ingestão total de energia, proteínas, carboidratos e lipídios nestes pacientes mesmo quando foram divididos de acordo com o grau de inflamação, esteatose e ENA. Por outro lado, a CC ao ser correlacionada com IMC (p=0,000), HOMA (p=0,049), ingestão total de energia (p=0,043), lipídios e dos ácidos graxos mono (p=0,020) e poliinsaturados (0,045) apresentaram significância estatística nos pacientes com DHGNA. Quando divididos segundo o grau de esteatose houve correlação positiva entre CC e HOMA (p=0,045) nos pacientes com esteatose simples. Já nos pacientes portadores de ENA houve correlação positiva entre CC e ingestão total de calorias (p=0,031). Houve diferença estatística positiva quanto ao consumo de lipídios totais (p=0,005) entre o grupo de esteatose e ENA, onde os pacientes com ENA, tinham um maior consumo de lipídios. Conclusões: A circunferência de cintura se mostrou melhor parâmetro de diagnóstico complementar ao ser comparado com a tomografia computadorizada em pacientes com DHGNA. Ao associarmos o IMC com a CC conseguimos obter uma avaliação nutricional mais fidedigna dos riscos de doenças decorrentes da síndrome metabólica. O alto consumo de lipídios apresentou correlação positiva com maior grau de inflamação em pacientes com DHGNA. / Introduction: The dramatic increasing of obesity in the world is a predictive factor to increase the prevalence of chronic diseases, as type II diabetes, hypertension and Nonalcoholic fatty liver disease (NAFLD). It is part of large spectrum of liver damage ranging from simple steatosis and cirrhosis. The pathogenesis of NAFLD is multifactorial and some points in the mechanisms and therapeutic still unknown. The insulin resistance is the major risk factors, recognized in the pathophysiology of NAFLD and it is strongly related with life style and diet. Objective: Evaluate the correlation between visceral and subcutaneous fat with insulin resistance, presence of metabolic syndrome, anthropometric measurements and dietary intake in patients with NAFLD. Results: Sixty percent of patients with NAFLD, classified by ATPIII criteria, had the metabolic syndrome. Waist circumference and low HDL -C were the most positive criteria, observed in 56% of total cases. However the criteria modifies when the group were divided. In patients with simple steatosis WC was the most prevalent criteria 77%, where as in NASH patients the high level of TGL 68%, was the most prevalent. Correlations between CT and BMI (p=0,001), WC (p=0,033) and fat mass (p =0,031) had a negative statistic significant correlation in all cases of NAFLD. No significant associations were found between CT (umbilical circumference) and fat mass, WC, HOMA, Intake of calories, carbohydrates, proteins, lipids and fat acids in patients divided in steatosis and NASH patients. The correlation between Waist circumference (WC) with BMI (p=0,000), HOMA (p:0,049), total of energy intake (p=0,043) , monounsaturated (p:0,020) and polyunsaturated (p:0,045) fat acids intake showed a statistic significance in all cases of NAFLD. Significant different correlations were found as the group were divided in steatosis and NASH cases. The values of fat mass correlated with WC was (p: 0,045) in the steatosis group where as in NASH patients the only correlation found was WC and total consumption of daily energy (p=0,031). NASH patients showed a statistic higher intake of lipids (p=0,005), compared with steatosis patients. Conclusions: CT measurement of visceral fat did not contribute to differential diagnosis as much as WC in patients with NAFLD. The use of both measurements BMI and WC showed to be a better predictor of the risks of Metabolic Syndromes. NASH subjects had a higher intake o total fat as well as of lipid fractions.

Application of smart curing concept called internal curing (IC) is the most promising strategy for mitigating autogenous shrinkage and related early-age cracking in cement-based materials with low water-to-cement ratio. There are still many theoretical and practical questions that need to be answered before IC could become a standard method. Many of these questions concern the most appealing of water-regulating additives for IC called Superabsorbent Polymers (SAP). The clear linkage between SAP material properties, the moment of water release and the effect on autogenous shrinkage is still missing, which blocks formulating recommendations for use of particular potential IC agents in concrete construction. In this treatise various aspects that are decisive for effectiveness of IC in mitigating autogenous shrinkage were examined. The choice of materials was purposefully limited to two compositions of Ultra-High Performance Concrete (UHPC), one fine-grained and one coarse-grained mixture, and one particular, in-depth characterized SAP. The objectives of examination which shaped the final experimental programme were: assessment of IC agent absorption capacity, specification of periods of water migration from fresh concrete mixture into SAP and from SAP back into hardening concrete, determination of effect of SAP addition on cement hydration, evaluation of IC influence on and determination of start of effective autogenous shrinkage and, finally, assessment of autogenous shrinkage with selfsame IC agent but for different matrices. Ideally, description of the mechanisms behind the action of IC at different stages of concrete life and reasoning of differences observed for the UHPCs under investigation had to be provided. First, the main components of the system – UHPC and SAP material – were characterized as to their suitability for IC application. Special attention was paid to the material properties which affect water transport. Usage of different testing methods was necessary here and included: testing with ESEM, FT-IR, tea-bag test, sol fraction content examination and X-ray computed tomography (for SAP) as well as air content measurement and various methods for characterization of the porosity and other features of the microstructure. The observed delay in the start of pozzolanic reactions in case of fine-grained UHPC was rather surprising, but, under consideration of porosity, shed new light on permeability of young UHPC. The work at hand revealed numerous methods that can be used for studying the absorption capacity of polymers, but hardly representative for the behaviour of those polymers within concrete matrix. Because of its general availability and the relatively robust testing procedure, it was decided to focus on possibilities and limitations of using tea-bag test for evaluation of absorption capacity of SAP. New interpretation of tea-bag test results was deduced which enabled assessment of maximum absorption capacity of SAP from measurement of consistency of concrete before and after modification with IC. Influence of IC on hydration process was revealed by using two non-destructive methods, in particular ultrasonic measurement and concrete temperature record. It could be shown that the ionic polymer exhibits complex effects including retardation and acceleration of individual chemical processes. Additionally, X-ray computed tomography (CT) and instrumented ring tests were performed in order to understand scientific significance of the characteristic event appearing during shrinkage measurements, taken as time-zero (= starting point for evaluation of autogenous shrinkage data). Linkage of time-zero with certain phenomenon, e.g., changes of the SAP particles volume or specific value of yield stress, but not with final set, was suggested for the future investigations. By using two setups based on corrugated tube protocol it was possible to register and compare autogenous shrinkage of both UHPCs without and with modification by IC. The effectiveness of IC was shown to be dependent on the matrix in which IC was implemented. This was related to the observed changes in pore percolation that resulted from different absorption behaviour of SAP in the two UHPCs under investigation. Furthermore, the effect of fibres on effectiveness of IC was discussed. Description and discussion of mechanisms behind IC was supported by measurement of capillary pressure, total shrinkage tests with simultaneous mass loss measurement, free autogenous shrinkage tests and the CT measurement. Valuable source of information was furthermore the in-depth literature review. The most appealing finding of the work and the biggest paradox revealed was high efficiency of IC in mitigating autogenous shrinkage and simultaneously appearance of stage where very clear reverse in mode of polymer volume change was observed. This suggests partial reabsorption of water initially released. This puts interpretation of operative shrinkage mechanisms and ones standing behind IC effect in a new perspective. / Die innere Nachbehandlung (Internal Curing – IC) ist die derzeit aussichtsreichste Strategie, um das in zementgebundenen Baustoffen mit niedrigen Wasser/Zement-Werten ausgeprägt auftretende autogene Schwinden wirksam zu verringern und die damit einhergehende Rissbildung in jungem Beton zu vermeiden. Vor einer breiten baupraktischen Anwendung des IC sind noch viele offene Fragen zu beantworten. Die meisten dieser Fragen betreffen die derzeit interessanteste Klasse von wasserregulierenden Stoffen für das IC – die superabsorbierenden Polymere (SAP). Von entscheidender Bedeutung ist hier der noch weitgehend unerforschte Zusammenhang zwischen den Materialeigenschaften der SAP, dem Zeitpunkt der Wasserabgabe und der Auswirkung auf das autogene Schwinden. In der vorliegenden Arbeit werden verschiedene Einflussfaktoren auf die Wirksamkeit von SAP zur Verringerung des autogenen Schwindens untersucht. Für die Experimente wurde ein feinkörniger und ein grobkörniger ultra-hochfester Beton (UHPC) sowie ein schon detailliert charakterisiertes SAP genutzt. Das experimentelle Programm wurde auf folgende Untersuchungsziele ausgerichtet: Absorptionsvermögen der SAP, Zeitfenster der Wassermigration aus dem Frischbeton in das SAP sowie vom SAP in den erhärtenden Beton, autogenes Schwindmaß sowie effektiver Beginn des autogenen Schwindens. Ziel der Arbeiten ist die Beschreibung der Mechanismen, die IC zugrundliegen – und dies zu verschiedenen Betonaltern und unter Berücksichtigung der an den untersuchten UHPC beobachteten Unterschiede. Bei der Charakterisierung der Hauptkomponenten des betrachteten Systems – UHPC und SAP – wurde auf die Materialeigenschaften fokussiert, die den Wassertransport beeinflussen. Dazu wurden u. a. folgende Untersuchungsmethoden angewendet: ESEM, FT-IR, Teebeuteltest, Sol-Fraction Test, Röntgentomographie (für SAP) sowie verschiedene Verfahren zur Charakterisierung der Poren im Beton. Im feinkörnigen UHPC wurde überraschenderweise ein verzögerter Beginn der puzzolanischen Reaktion festgestellt, der bei Berücksichtigung der vorliegenden Porosität zu einer Neubewertung der Permeabilität von UHPC in jungem Alter führte. In der vorliegenden Arbeit werden verschiedene Methoden zur Beschreibung des Wasserabsorptionsvermögens von SAP benannt, deren Aussagekraft bei Anwendung dieser Polymere im Beton aber sehr eingeschränkt ist. Aufgrund seiner einfachen Verfügbarkeit und Robustheit wurde daher der Teebeutetest zur Bestimmung der Wasserabsorption des SAP genutzt. Die Wasserabsorption der SAP im Beton wurde durch Gegenüberstellung von Konsistenzmessungen am Beton vor und nach Zugabe von SAP und Ergebnissen der Teebeuteltest abgeschätzt. Der Einfluss des IC auf die Hydratation wurde zerstörungsfrei mit Ultraschall- und Betontemperaturmessungen erfasst. Auf dieser Grundlage konnten Hypothesen zu den komplexen Wechselwirkungen zwischen ionischem Polymer und der Beschleunigung oder Verzögerung einzelner chemischer Prozesse formuliert werden. Mit Hilfe von instrumentierten Ringversuchen und X-ray Computertomographie wurden die Auswirkungen des IC mit SAP auf das autogene Schwinden, den Aufbau von Zwangsspannungen bei behindertem Schwinden und Time-Zero diskutiert. Dabei konnte ein Zusammenhang zwischen Time-Zero und verschiedenen Phänomenen, wie z. B. Volumenänderung des SAP oder der Fließgrenze des erhärtenden Betons, nicht aber zum Ende des Erstarrens aufgezeigt werden. Das autogene Schwinden beider untersuchter UHPC (jeweils mit und ohne IC) wurde mit Hilfe von Corrugated Tube-Versuchen gemessen. Es konnte gezeigt werden, dass wie Wirksamkeit des IC von der Betonzusammensetzung sowie der in den UHPC infolge Wechselwirkungen mit den SAP verschieden ausgebildeten Porenstruktur der Matrix abhängt. Weiterhin konnte ein Einfluss von Faserzugaben auf die Wirksamkeit des IC gezeigt werden. Die Beschreibung und Diskussion der Mechanismen des IC wurde durch Messungen des Kapillardrucks, des Gesamtschwindens, des freien autogenen Schwindens, des Masseverlustes und Computertomographie unterstützt. Eine wichtige Erkenntnisquelle war zudem die umfangreich gesichtete und diskutierte Literatur. Das interessanteste und zugleich paradoxe Ergebnis der Untersuchungen ist die Tatsache, dass die bei Einsatz von SAP beobachtete Verringerung des autogenen Schwindens eindeutig mit einer zeitgleichen Umkehr der Volumenänderung der SAP einhergeht: die bis dahin dominierende Wasserabgabe geht in eine erneute Wasseraufnahme über. Dies stellt die Interpretation der Triebkräfte des Schwindens und die dem IC zugrundliegenden Mechanismen in einen neuen Zusammenhang.

This diploma thesis deals with reduction of metal artifacts in CT data with submicron resolution. The first part of this thesis briefly describes x-ray computed tomography followed by the description of artifacts of tomographic images and existing approaches of the reduction of metal artifacts. In the second part proposed methods of reduction of metal artifacts and their implementation in Matlab programming environment are described. Finally functionality of algorithms is tested on a newly created database and the results are compared, evaluated and discussed.

X-Ray Computed Tomography is irreplaceable medical imaging system. Quantitative evaluation is day to day routine used for clean run of this imaging system. The master’s thesis is focused on quantitative evaluation of first and third generation X-Ray CT. First of all is about subjective and objective evaluation of space and energetic resolution. Space resolution is evaluated in space and frequency domain. Energetic resolution is represent by low contrast resolution method. Application “Kvantitativní hodnocení kvality CT RTG zobrazení” created for this thesis is used for creation of reconstruction image and quantitative evaluation. This application was created with consideration of its usage in subjects about image processing. The master’s thesis contains results of quantitative evaluation X-Ray CT created with this application and proposal of lab work.

The work deals with physical principles of X-ray generation and development of image during projection and projection reconstruction. A proposal of user’s application in a Matlab – Guide is given, which can be used as a laboratory exercise of the simulation of the projection- and projection image reconstruction. The computer program involves an evaluation of a X-ray quality of CT RTG ZS – quantitative assessment of spatial resolution and as well as the acquisition contrast as a function on an object size. The main aim of the work was the comparison of the acquisition contrast at various acquisition projection and projection-reconstruction parameters. Also, the work is illustrated by some results achieved.

Text in English / The destructive nature of conventional analytical techniques, coupled with the finite nature of ancient/historical artefacts, has long restricted technical examinations of museum collections, mainly due to ethical constraints. However, over the past few decades, the application of Non-Destructive Evaluation (NDE) techniques has become increasingly popular within the fields of archaeology and cultural heritage diagnostics. The application of such techniques has facilitated the examination of objects that have long remained uninvestigated. However, this positive development also held a slight drawback, in that researchers tend to now focus on technical analyses alone, while excluding more traditional means of analyses, such as comparative stylistic analysis and surface investigation. By employing a combination of stylistic analysis, visual surface investigation (by means of SLR photography and digital microscopy) and nuclear imaging (by means of Microfocus X-Ray Computed Tomography), the thesis sets out to justify the application of mixed methodologies as part of a more holistic integrated authentication approach. Thus stated, the thesis presents a mixed-methodological approach towards the analysis of selected metal objects from the Ditsong National Museum of Cultural History in Pretoria, South Africa. The objects under investigation include a small collection of ancient Egyptian bronze statuettes, a Samurai helmet (kabuto) and mask (menpó), a European gauntlet, and an Arabian dagger (jambiya/khanjar). While all the objects are curated as part of the museum‘s archaeology and military history collections, the exact production dates, manufacturing techniques and areas of origin remain a mystery. By using a combination of techniques, the thesis aims to identify diagnostic features that can be used to shed light on their relative age, culturo-chronological framework and, by extension, their authenticity. / Old Testament and Ancient Near Eastern Studies / D. Litt. et Phil.(Ancient Near Eastern Studies)

No description available.

Application of smart curing concept called internal curing (IC) is the most promising strategy for mitigating autogenous shrinkage and related early-age cracking in cement-based materials with low water-to-cement ratio. There are still many theoretical and practical questions that need to be answered before IC could become a standard method. Many of these questions concern the most appealing of water-regulating additives for IC called Superabsorbent Polymers (SAP). The clear linkage between SAP material properties, the moment of water release and the effect on autogenous shrinkage is still missing, which blocks formulating recommendations for use of particular potential IC agents in concrete construction. In this treatise various aspects that are decisive for effectiveness of IC in mitigating autogenous shrinkage were examined. The choice of materials was purposefully limited to two compositions of Ultra-High Performance Concrete (UHPC), one fine-grained and one coarse-grained mixture, and one particular, in-depth characterized SAP. The objectives of examination which shaped the final experimental programme were: assessment of IC agent absorption capacity, specification of periods of water migration from fresh concrete mixture into SAP and from SAP back into hardening concrete, determination of effect of SAP addition on cement hydration, evaluation of IC influence on and determination of start of effective autogenous shrinkage and, finally, assessment of autogenous shrinkage with selfsame IC agent but for different matrices. Ideally, description of the mechanisms behind the action of IC at different stages of concrete life and reasoning of differences observed for the UHPCs under investigation had to be provided. First, the main components of the system – UHPC and SAP material – were characterized as to their suitability for IC application. Special attention was paid to the material properties which affect water transport. Usage of different testing methods was necessary here and included: testing with ESEM, FT-IR, tea-bag test, sol fraction content examination and X-ray computed tomography (for SAP) as well as air content measurement and various methods for characterization of the porosity and other features of the microstructure. The observed delay in the start of pozzolanic reactions in case of fine-grained UHPC was rather surprising, but, under consideration of porosity, shed new light on permeability of young UHPC. The work at hand revealed numerous methods that can be used for studying the absorption capacity of polymers, but hardly representative for the behaviour of those polymers within concrete matrix. Because of its general availability and the relatively robust testing procedure, it was decided to focus on possibilities and limitations of using tea-bag test for evaluation of absorption capacity of SAP. New interpretation of tea-bag test results was deduced which enabled assessment of maximum absorption capacity of SAP from measurement of consistency of concrete before and after modification with IC. Influence of IC on hydration process was revealed by using two non-destructive methods, in particular ultrasonic measurement and concrete temperature record. It could be shown that the ionic polymer exhibits complex effects including retardation and acceleration of individual chemical processes. Additionally, X-ray computed tomography (CT) and instrumented ring tests were performed in order to understand scientific significance of the characteristic event appearing during shrinkage measurements, taken as time-zero (= starting point for evaluation of autogenous shrinkage data). Linkage of time-zero with certain phenomenon, e.g., changes of the SAP particles volume or specific value of yield stress, but not with final set, was suggested for the future investigations. By using two setups based on corrugated tube protocol it was possible to register and compare autogenous shrinkage of both UHPCs without and with modification by IC. The effectiveness of IC was shown to be dependent on the matrix in which IC was implemented. This was related to the observed changes in pore percolation that resulted from different absorption behaviour of SAP in the two UHPCs under investigation. Furthermore, the effect of fibres on effectiveness of IC was discussed. Description and discussion of mechanisms behind IC was supported by measurement of capillary pressure, total shrinkage tests with simultaneous mass loss measurement, free autogenous shrinkage tests and the CT measurement. Valuable source of information was furthermore the in-depth literature review. The most appealing finding of the work and the biggest paradox revealed was high efficiency of IC in mitigating autogenous shrinkage and simultaneously appearance of stage where very clear reverse in mode of polymer volume change was observed. This suggests partial reabsorption of water initially released. This puts interpretation of operative shrinkage mechanisms and ones standing behind IC effect in a new perspective. / Die innere Nachbehandlung (Internal Curing – IC) ist die derzeit aussichtsreichste Strategie, um das in zementgebundenen Baustoffen mit niedrigen Wasser/Zement-Werten ausgeprägt auftretende autogene Schwinden wirksam zu verringern und die damit einhergehende Rissbildung in jungem Beton zu vermeiden. Vor einer breiten baupraktischen Anwendung des IC sind noch viele offene Fragen zu beantworten. Die meisten dieser Fragen betreffen die derzeit interessanteste Klasse von wasserregulierenden Stoffen für das IC – die superabsorbierenden Polymere (SAP). Von entscheidender Bedeutung ist hier der noch weitgehend unerforschte Zusammenhang zwischen den Materialeigenschaften der SAP, dem Zeitpunkt der Wasserabgabe und der Auswirkung auf das autogene Schwinden. In der vorliegenden Arbeit werden verschiedene Einflussfaktoren auf die Wirksamkeit von SAP zur Verringerung des autogenen Schwindens untersucht. Für die Experimente wurde ein feinkörniger und ein grobkörniger ultra-hochfester Beton (UHPC) sowie ein schon detailliert charakterisiertes SAP genutzt. Das experimentelle Programm wurde auf folgende Untersuchungsziele ausgerichtet: Absorptionsvermögen der SAP, Zeitfenster der Wassermigration aus dem Frischbeton in das SAP sowie vom SAP in den erhärtenden Beton, autogenes Schwindmaß sowie effektiver Beginn des autogenen Schwindens. Ziel der Arbeiten ist die Beschreibung der Mechanismen, die IC zugrundliegen – und dies zu verschiedenen Betonaltern und unter Berücksichtigung der an den untersuchten UHPC beobachteten Unterschiede. Bei der Charakterisierung der Hauptkomponenten des betrachteten Systems – UHPC und SAP – wurde auf die Materialeigenschaften fokussiert, die den Wassertransport beeinflussen. Dazu wurden u. a. folgende Untersuchungsmethoden angewendet: ESEM, FT-IR, Teebeuteltest, Sol-Fraction Test, Röntgentomographie (für SAP) sowie verschiedene Verfahren zur Charakterisierung der Poren im Beton. Im feinkörnigen UHPC wurde überraschenderweise ein verzögerter Beginn der puzzolanischen Reaktion festgestellt, der bei Berücksichtigung der vorliegenden Porosität zu einer Neubewertung der Permeabilität von UHPC in jungem Alter führte. In der vorliegenden Arbeit werden verschiedene Methoden zur Beschreibung des Wasserabsorptionsvermögens von SAP benannt, deren Aussagekraft bei Anwendung dieser Polymere im Beton aber sehr eingeschränkt ist. Aufgrund seiner einfachen Verfügbarkeit und Robustheit wurde daher der Teebeutetest zur Bestimmung der Wasserabsorption des SAP genutzt. Die Wasserabsorption der SAP im Beton wurde durch Gegenüberstellung von Konsistenzmessungen am Beton vor und nach Zugabe von SAP und Ergebnissen der Teebeuteltest abgeschätzt. Der Einfluss des IC auf die Hydratation wurde zerstörungsfrei mit Ultraschall- und Betontemperaturmessungen erfasst. Auf dieser Grundlage konnten Hypothesen zu den komplexen Wechselwirkungen zwischen ionischem Polymer und der Beschleunigung oder Verzögerung einzelner chemischer Prozesse formuliert werden. Mit Hilfe von instrumentierten Ringversuchen und X-ray Computertomographie wurden die Auswirkungen des IC mit SAP auf das autogene Schwinden, den Aufbau von Zwangsspannungen bei behindertem Schwinden und Time-Zero diskutiert. Dabei konnte ein Zusammenhang zwischen Time-Zero und verschiedenen Phänomenen, wie z. B. Volumenänderung des SAP oder der Fließgrenze des erhärtenden Betons, nicht aber zum Ende des Erstarrens aufgezeigt werden. Das autogene Schwinden beider untersuchter UHPC (jeweils mit und ohne IC) wurde mit Hilfe von Corrugated Tube-Versuchen gemessen. Es konnte gezeigt werden, dass wie Wirksamkeit des IC von der Betonzusammensetzung sowie der in den UHPC infolge Wechselwirkungen mit den SAP verschieden ausgebildeten Porenstruktur der Matrix abhängt. Weiterhin konnte ein Einfluss von Faserzugaben auf die Wirksamkeit des IC gezeigt werden. Die Beschreibung und Diskussion der Mechanismen des IC wurde durch Messungen des Kapillardrucks, des Gesamtschwindens, des freien autogenen Schwindens, des Masseverlustes und Computertomographie unterstützt. Eine wichtige Erkenntnisquelle war zudem die umfangreich gesichtete und diskutierte Literatur. Das interessanteste und zugleich paradoxe Ergebnis der Untersuchungen ist die Tatsache, dass die bei Einsatz von SAP beobachtete Verringerung des autogenen Schwindens eindeutig mit einer zeitgleichen Umkehr der Volumenänderung der SAP einhergeht: die bis dahin dominierende Wasserabgabe geht in eine erneute Wasseraufnahme über. Dies stellt die Interpretation der Triebkräfte des Schwindens und die dem IC zugrundliegenden Mechanismen in einen neuen Zusammenhang.