Technische Universität Bergakademie Freiberg: Qucosa
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Minimum participation requirements and the role of co-benefits in international climate policy
No full textEffective combat of international environmental problems regularly necessitates a minimum number of participating countries. Some international environmental treaties like the Paris Agreement combating global warming and the Montreal Protocol protecting the ozone layer required that a minimum participation threshold be met before they entered into force. Albeit the immense challenge to protect the global climate, the Paris Agreement additionally demands to address sustainable development and therefore seeks to take advantage of potential co-benefits of climate protection measures. This article is, to the authors' knowledge, the first to investigate in 3 × 3 normal form games the prospects for effective international cooperation on climate protection if effectiveness requires a minimum number of participating countries. The main findings are, first, that sustainable development co-benefits from mitigation might increase the chance that the minimum participation threshold is met and climate policy will be effective in the end; and second, if domestic ancillary benefits from mitigation are rather small, new organizational designs could create additional sustainability benefits that are limited to mitigating countries. For example, a win-win situation – regarding climate and sustainability – could be achieved by international policy designs that create additional co-benefit spillovers via the establishment of a club pursuing sustainable innovations (in line with UN Sustainable Development Goal 9)
Electrochemical Sensing Based on Nanofibers Modified Electrodes for Application in Diagnostic, Food and Waste Water Samples
No full textElectrochemical sensors and biosensors are today important analytical and monitoring tools in various fields, from agriculture and the food industry to environmental and biomedical/pharmaceutical applications. In particular, the integration of nanotechnology with electrochemical sensors and biosensors to develop a new generation of sensor platforms has made enormous progress in recent years. The outstanding properties of one-dimensional (1D) nanofibers (NFs), such as high porosity, superior mechanical properties and high specific surface area have made them attractive electrocatalysts, support materials for the immobilization of biomolecules as well as mimetic materials for sensing and biosensing applications. Moreover, the possibility of fabricating multifunctional composites based on NFs increases (bio)sensing capabilities through synergistic effects and additive properties. This review describes the progress made over the last decade in the use of multifunctional NFs-based composites as modified electrodes for the sensing of various analytes in biomedical, food, and wastewater treatment applications. The aim of this review is to provide a comprehensive overview and a guide for researchers from different disciplines to fabricate and improve their selective NFs-based (bio)sensor platforms for the detection of desired analytes or multi-analytes
Predatory Publishing - wenn Wissenschaft zur Beute wird
No full textDie Digitalisierung und die Open-Access-Bewegung haben den Zugang zu wissenschaftlichem Wissen maßgeblich erleichtert und neue Publikationswege eröffnet.
Gleichzeitig nutzen unseriöse Anbieter diese offenen Strukturen aus. In dieser Ausgabe rücken wir daher das Thema Predatory Publishing in den Fokus, um für diese Gefahr zu sensibilisieren und praxisnahe Werkzeuge vorzustellen, mit denen Forschende solche betrügerischen Praktiken erkennen können
Scale Transition Behavior of Phase-Field Models for Phase Transforming Solids
No full textPhase transforming solids represent a unique class of multi-functional materials, that are known for their remarkable thermo-mechanical properties. They exhibit an evolution of microstructure under specific stress- and temperature conditions, which stems from microscopic phase transitions between different types of parent and product phases. Moreover, the corresponding transformation mechanisms are associated with a dissipation of energy and therefore give rise to a hysteretic behavior. As observed in experiments, resulting stress-strain and undercooling curves typically suggest a rate-independent response to quasi-static loading, so that hysteresis loops obtain a finite width even as the external loading rate approaches zero. Over the past few decades, the phase-field method has emerged as a powerful modeling framework, effectively capturing and resolving the evolution of complex interface topologies in phase transforming solids. Despite many important scientific contributions in this regard, most existing models employ rate-dependent dissipation formulations, thus limiting their ability to accurately replicate thermo-elastic hysteresis loops under quasi-static loading conditions. In addition, large-scale simulations are usually associated with enormous computational costs, since the involved temporal and spatial scales need to be resolved numerically with sufficient accuracy. Consequently, the embedding of existing routines into modern two-scale approaches, such as the FE²-method, is immensely constrained by technical limitations. Moreover, a general notion for consistently transferring specific phase-field models between multiple, variable scales has still not been fully developed.
To overcome these issues, this work presents a thermo-mechanically coupled and thermodynamically consistent phase-field approach that incorporates both rate-dependent and -independent driving force formulations. The proposed model is shown to effectively capture superelastic stress-strain loops, sigmoidal-like undercooling hysteresis as well as stress- and temperature-induced martensite pattern formation. To demonstrate the practical applicability of the outlined approach, two-dimensional finite element simulations of a ZrO2-like material are conducted to study the microstructure formation of twinned martensite. In addition, a new homogenization framework for phase transforming materials is introduced, which involves the concepts of phase-morphology and variable scale separations. More specifically, it is mathematically demonstrated that macroscopic driving forces as well as effective mechanical properties can be expressed as functions of the averaged martensite volume fraction and, additionally, of a finite collection of weighted phase averages. Whereas conventional homogenization schemes only evaluate the stationary, fully-relaxed system state, the framework presented in this work is capable of deriving effective properties for phase transforming materials even during the phase evolution process.:1. Introduction
1.1. State of the Art
1.2. Scope of this Thesis
2. Fundamentals of Continuum Mechanics and Thermodynamics
2.1. Kinematics
2.1.1. Spacetime and Observers
2.1.2. Material Bodies and Motion
2.1.3. Deformation
2.1.4. Material Rates
2.1.5. Objectivity
2.2. Balance Principles
2.2.1. Master Balance Principles
2.2.2. Balance of Mass
2.2.3. Balance of Linear Momentum
2.2.4. Balance of Angular Momentum
2.2.5. Balance of Microforces
2.2.6. Balance of Energy
2.2.7. Balance of Entropy
2.3. Coleman-Noll Procedure
2.3.1. Standard Cauchy Continua
2.3.2. Generalized Continua
3. Phase-Field Modeling of Rate-(In)Dependent Systems
3.1. Diffuse Interface Approximation
3.2. Phase Evolution Laws
3.2.1. Allen-Cahn Systems
3.2.2. Cahn-Hilliard Systems
3.2.3. Thermodynamic Thresholds
3.2.4. Thermo-Mechanically Coupled Allen-Cahn Systems
3.2.5. Weak Form of the Initial-Boundary Value Problem
3.2.6. Finite Element Implementation
4. Scale Transition Behavior of Phase Evolution Laws
4.1. The Concept of Phase-Morphology
4.1.1. Sets of Admissible Phase Distributions
4.1.2. Phase-Morphological State Vector
4.1.3. Martensite Orientation as a Phase-Morphology
4.2. Homogenization of Phase Transforming Systems
4.2.1. Homogenization Problem
4.2.2. Macroscopic Driving Forces
4.2.3. Macroscopic Elastic Properties
4.3. Variable Scale Separation
4.3.1. Unweighted Scale Equivalence Principle
4.3.2. Weighted Scale Equivalence Principle
5. Conclusions and Outlook
A. Mathematical Preliminaries
B. Spatial Derivatives of Shape FunctionsPhasenumwandelnde Festkörper stellen eine einzigartige Klasse von Multifunktionswerkstoffen dar, welche sich durch bemerkenswerte thermomechanische Eigenschaften auszeichnen. Unter bestimmten Spannungs- und Temperaturbedingungen weisen diese eine Entwicklung in ihrer Mikrostruktur auf, die auf mikroskopische Phasenübergänge zwischen verschiedenen Ausgangs- und Produktphasenzuständen zurückzuführen ist. In quasi-statischen Experimenten zeigen die resultierenden Spannungs-/Dehnungs- und Unterkühlungskurven typischerweise ratenunabhängiges Verhalten, so dass die damit verbundenen Hystereseschleifen eine endliche Breite besitzen, selbst wenn die Belastungsrate gegen Null konvergiert. In den letzten Jahrzehnten hat sich die Phasenfeldmethode als ein leistungsfähiges Modellierungs-Tool etabliert, mit dem die Entwicklung komplexer Grenzflächentopologien in phasenumwandelnden Festkörpern mathematisch abgebildet und numerisch präzise aufgelöst werden kann. Trotz einer Vielzahl von bedeutenden Beiträgen auf diesem Forschungsgebiet, wird in den meisten Modellen eine ratenabhängige Dissipationsformulierung verwendet, wodurch thermoelastische Hystereseschleifen unter quasi-statischer Belastung nicht abgebildet werden können. Darüber hinaus sind großskalige Simulationen in der Regel mit einem enormen Rechenaufwand verbunden, da die intrinsischen Zeit- und Raumskalen numerisch mit entsprechender Genauigkeit aufgelöst werden müssen. Demzufolge ist die Einbettung bestehender Routinen in moderne Zwei-Skalen-Ansätze, wie beispielsweise die FE²-Methode, auf Grund rechentechnischer Limitierungen immens eingeschränkt. Zudem existiert bisher kein allgemeines Konzept zur konsistenten Formulierung des Übergangs eines spezifischen Phasenfeldmodells zwischen mehreren, variablen Skalen.
Zur Lösung dieser Probleme wird in der hier vorliegenden Arbeit ein thermo-mechanisch gekoppelter und thermodynamisch konsistenter Phasenfeldansatz vorgestellt, der sowohl ratenabhängige als auch -unabhängige Triebkraftformulierungen beinhaltet. Es wird gezeigt, dass somit superelastische Spannungs-Dehnungs-Schleifen, sigmodiale Unterkühlungshysteresen und auch spannungs- und temperaturinduzierte Martensitformationen effektiv erfasst werden können. Die praktische Anwendbarkeit des Ansatzes wird innerhalb zweidimensionaler Finite-Elemente-Simulationen eines ZrO2-ähnlichen Materials gezeigt, anhand derer die Mikrostrukturbildung von verzwillingtem Martensit untersucht werden kann. Desweiteren wird ein neuer Homogenisierungsrahmen für phasenumwandelnde Materialien vorgestellt, welcher die Konzepte der Phasen-Morphologie und variabler Skalenseparation beinhaltet. Damit ist es möglich sowohl makroskopische Triebkräfte, als auch effektive mechanische Eigenschaften als Funktionen des gemittelten Martensit-Volumenanteils, sowie einer endlichen Anzahl gewichteter Phasenmittelwerte darzustellen. Während herkömmliche Homogenisierungsansätze nur den stationären, vollständig relaxierten Systemzustand betrachten, ist die in dieser Arbeit vorgestellte Methode in der Lage effektive Eigenschaften auch während des Phasenentwicklungsprozesses abzuleiten.:1. Introduction
1.1. State of the Art
1.2. Scope of this Thesis
2. Fundamentals of Continuum Mechanics and Thermodynamics
2.1. Kinematics
2.1.1. Spacetime and Observers
2.1.2. Material Bodies and Motion
2.1.3. Deformation
2.1.4. Material Rates
2.1.5. Objectivity
2.2. Balance Principles
2.2.1. Master Balance Principles
2.2.2. Balance of Mass
2.2.3. Balance of Linear Momentum
2.2.4. Balance of Angular Momentum
2.2.5. Balance of Microforces
2.2.6. Balance of Energy
2.2.7. Balance of Entropy
2.3. Coleman-Noll Procedure
2.3.1. Standard Cauchy Continua
2.3.2. Generalized Continua
3. Phase-Field Modeling of Rate-(In)Dependent Systems
3.1. Diffuse Interface Approximation
3.2. Phase Evolution Laws
3.2.1. Allen-Cahn Systems
3.2.2. Cahn-Hilliard Systems
3.2.3. Thermodynamic Thresholds
3.2.4. Thermo-Mechanically Coupled Allen-Cahn Systems
3.2.5. Weak Form of the Initial-Boundary Value Problem
3.2.6. Finite Element Implementation
4. Scale Transition Behavior of Phase Evolution Laws
4.1. The Concept of Phase-Morphology
4.1.1. Sets of Admissible Phase Distributions
4.1.2. Phase-Morphological State Vector
4.1.3. Martensite Orientation as a Phase-Morphology
4.2. Homogenization of Phase Transforming Systems
4.2.1. Homogenization Problem
4.2.2. Macroscopic Driving Forces
4.2.3. Macroscopic Elastic Properties
4.3. Variable Scale Separation
4.3.1. Unweighted Scale Equivalence Principle
4.3.2. Weighted Scale Equivalence Principle
5. Conclusions and Outlook
A. Mathematical Preliminaries
B. Spatial Derivatives of Shape Function
Modular Methods for Efficient FE² Simulations
No full textNearly all materials possess a characteristic micro- resp. mesostructure at a certain length scale. The structural behavior, which is important for the design, is determined by the composition of this structure and its properties. In order to circumvent a full resolution of the microsctructure in structural models, homogenization theories can be deployed, which find the average behavior at the next higher scale.
If the finite element method (FEM) is utilized at both levels, the computationally expensive FE² scheme emerges. Hence, techniques are developed and applied throughout the present work, in order to mitigate the computational effort. Since the problem is caused by repetitive computer operations, algorithms which lower these recurrences are suitable in particular. Here, specifically a hyper integrated model order reduction method is applied and improvements of the selfsame are examined with the aim of lowering the effort of the needed calibration process and in the actual multiscale simulation. A concurrent, monolithic, hierarchical multiscale algorithm is established as the solver tool. The methods are designed such, that they are compatible with the modular structure of the FEM, especially in view of the strict separation between the global and element level.
The developed theory was implemented in an FEM program specifically designed for this work, which works together with Abaqus as the solver on the macroscale. Specific materials are investigated, by considering suitable self-provided resp. from the literature taken representative volume elements (RVEs) together with numerically efficiently treated and implemented material formulations applied in actual multiscale simulations, in order to on the one hand having benchmark examples for accuracy, flexibility and computational efficiency investigations and on the other hand showing how the methods are to be applied to actual engineering problems.:1. Introduction
1.1. Motivation
1.2. Overview of Micromechanics
1.2.1. History and Concepts
1.2.2. Analytical Homogenization
1.2.3. Numerical Homogenization and Scale Bridging
1.3. Aim and Scope
2. Theory
2.1. Continuum Mechanics
2.1.1. Preliminaries
2.1.2. Notation
2.1.3. Kinematics
2.1.4. Kinetics
2.1.5. Balance of Mass
2.1.6. Balance of Linear Momentum
2.1.7. Balance of Angular Momentum
2.1.8. Conjugated Stress Strain Measures
2.1.9. Boundary Conditions
2.1.10. Constitutive Laws
2.2. Multiscale Modeling
2.2.1. Homogenization: Scale Transition
2.2.2. Localization: Boundary Conditions
2.2.3. Rotation Free Localization
2.3. Finite Element Method
2.3.1. Fundamentals
2.3.2. Finite Element Method on the Microscale
2.3.3. Reduced-Order Modeling
2.3.4. ECM Hyper Integration: State of the Art
2.3.5. Generalized Hyper Integration Criteria
2.3.6. Empirical Hyper Element Integration Method (EHEIM)
2.3.7. Clustered Training Trajectories
2.3.8. Finite Element Method on the Macroscale
2.3.9. Monolithic Solution Strategy
2.4. Constitutive Laws at the Microscale
2.4.1. Preliminaries
2.4.2. v. Mises Elasto-Plasticity
2.4.3. Power Law Creep
2.4.4. Viscoelastic-Viscoplastic Damage of a Thermoplastic Polymer
2.4.5. Anisotropic Damage and Inelasticity in Unidirectional Composites
3. Implementation
3.1. Multiscaling in Commercial Software: State of the Art
3.2. Requirements for an FE2 Software
3.3. MonolithFE2: An FE2 Software for Abaqus
3.4. Outlook
4. Applications and Numerical Investigations
4.1. General Remarks
4.2. Porous Elasto-Plastic Composite
4.3. Hyperelastic Porous Strip
4.4. Woven Composite Structures
4.4.1. Objectives
4.4.2. Numerical Investigations with the ImplEx Thermoplastic Routine
4.4.3. Numerical Investigations with the ImplEx Yarn Routine
4.4.4. EHEIM ROM FE2 Simulations and Comparison with Experiments
4.5. Influence of the Foam Morphology on the Mechanical Behavior of Foam Filters
4.5.1. Application and Modeling of Ceramic Flow-Through Foam Filters
4.5.2. Fluid Mechanics
4.5.3. Selected Foams
4.5.4. Maximum Local Stresses
4.5.5. Foam Parameter Estimation
4.5.6. Polar Orthotropic Mindlin Plate
4.5.7. Results
4.5.8. Benchmark Investigations with the FE2 Method at Finite Deformations
5. Conclusion and Outlook
5.1. Findings
5.2. Outloo
Investigations on the Influence of Subsequent Electron Beam (EB) Remelting on the Microstructure of an Aluminium Nitride Layer Formed on an Aluminium Substrate (Part II)
No full textNitriding of Al alloys leads to the formation of a thin, hard nitride layer (AlN) on the surface. A subsequent EBR can both eliminate the nitriding-related cavities under the nitride layer and increase the hardness of the substrate without melting or destroying the nitride layer. This paper deals with investigations regarding the influence of the energy/heat input on the microstructure within both the AlN layer and the remelted Al substrate. Of particular interest was the interface between the AlN and the Al substrate, which changed to a transition zone with a depth of approximately 80 µm. A range of high-resolution imaging and analytical tools for both scanning and transmission electron microscopy were used for these investigations. Based on the findings from the microstructural investigations, a schematic model was developed of the processes occurring within the nitride layer and at the interface as a result of remelting
Multiaxial Constitutive Modeling of Basal Textured Wrought Magnesium Alloys
No full textThis thesis is dedicated to the multiaxial constitutive modeling of basal textured wrought magnesium (Mg) alloys. Twin-roll-cast Mg alloys typically exhibit a significant basal texture as a result of the manufacturing process. Depending on the direction of load, plastic deformation can occur by activating dislocation slip or twinning. The pronounced basal texture and load direction-dependent plastic deformation mechanisms lead to anisotropic and asymmetric plastic material behavior. Furthermore, in recent research, a pronounced strain localization has been observed in the form of macroscopic bands of twinned grains (BTGs), where the compressive strain is approximately 600 % higher than in adjacent areas. The fatigue behavior is significantly affected by BTGs. However, their local elasto-plastic material behavior remains largely unexplored both experimentally and numerically. The objective of this study is to conduct an experimental analysis of the global and local elasto-plastic material behavior for uniaxial and biaxial stress states, with particular emphasis on anisotropic and asymmetric properties. Additionally, the study aims to establish a constitutive model for finite element method simulation, which encompasses both the anisotropic and asymmetric material behavior as well as the pronounced strain localization.
Therefore, strain-controlled uniaxial tensile and compression tests were performed in both the rolling (RD) and transverse directions (TD). In-situ strain field measurements were performed using digital image correlation (DIC) to locally evaluate the three-dimensional evolution of plastic deformations in the BTGs. The results of the uniaxial compression tests demonstrate that macroscopic plastification takes place exclusively in the BTGs, whereas the adjacent areas are mainly elastically deformed. Additionally, the BTGs exhibit a strong anisotropy in lateral plastic strains. The plastic Poisson’s ratio is 0 in the sheet mid-plane and 1 perpendicular to the sheet mid-plane. It can be stated that this is a fundamental plastic property for twinning. The deviation between the measured plastic Poisson’s ratios and the theoretical values is dependent on the intensity of the basal texture. In contrast, the gauge area of the uniaxial tensile sample exhibits a homogeneous strain field with nearly isotropic material behavior. Both the tensile and compression tests demonstrate plastic volume constancy.
A testing device is presented that allows not only biaxial tensile tests but also, for the first time, biaxial compression tests on thin-walled sheets. A cruciform sample was developed that ensures an almost homogeneous biaxial stress state in the gauge area. Furthermore, a novel anti-buckling device was developed to prevent the biaxial sample from buckling under compressive loading. In analogy to the uniaxial and shear tests, in-situ strain field measurements were performed in the gauge area to study the evolution of plastic deformations. The initial yield loci for calibrating the yield surface were determined using a numerical-experimental method. The findings from the equi-biaxial compression test prove that BTGs form similar to the uniaxial compression tests. Initially, the BTGs form perpendicular to the TD and exhibit a plastic Poisson’s ratio in the sheet plane of approx. 0. The initial biaxial yield stresses correspond approximately to the uniaxial compressive yield stresses. It was proven that the elasto-plastic material behavior can be modeled with a convex yield surface. At higher loads, BTGs are also formed perpendicular to the RD.
A three-dimensional, phenomenological, constitutive model was developed that accounts for the anisotropic and asymmetric plastic material behavior and the potential strain localization. The constitutive model was calibrated through the uniaxial and biaxial tests and subsequently validated with ten different FEM simulations. Tests of the constitutive model using one finite element show that the stress-strain relationship and plastic deformations can be validly calculated, for example, a total of four uniaxial and three biaxial stress states. The FEM simulation of a uniaxial compression sample shows that the discontinuous strain localization can be simulated on the macroscopic scale for the first time. This results in macroscopic bands with high plastic strain (BPDs) whose shape, volume, and propagation match those of the BTGs. Moreover, local state variables, such as stresses, plastic strains, and flow vectors in the BPD, correspond remarkably well to the experimentally measured state variables in the BTG. The validation of a notched specimen from the literature demonstrated that the cross-shaped strain localization in the form of BTGs can be reasonably well calculated. The accurate determination of the field quantities in the BTGs through FEM simulation, which is crucial for fatigue modeling, underscores the capability of the constitutive model
Aktivitäts- und Stabilitätsuntersuchungen kupferbasierter Feststoffkatalysatoren zur Methanolsynthese aus CO2/H2 im Gas- und Flüssigphasenprozess
No full textIn der vorliegenden Arbeit wurde das Desaktivierungsverhalten von Cu/ZnO/Al2O3-Katalysatoren sowohl im flüssigphasenunterstützten als auch im gasphasenbasierten CO2-Hydrierungsprozess zu Methanol und CO systematisch untersucht. Der Aktivitätsverlust wurde u. a. auf das Kristallitwachstum von Cu und ZnO zurückgeführt. Dieser Prozess findet aufgrund des wasserinduzierten Sinterns statt.
Zur Inhibierung der Desaktivierung wurden zwei Strategien verfolgt: Erstens wurde der Cu/ZnO/Al2O3-Katalysatoren mangandotiert. Dies resultierte in kleineren Kristalliten, einer erhöhten Kupfermenge an der Oberfläche und verbesserter Sinterresistenz bei Anwesenheit von Wasser. Allerdings zeigte sich keine signifikante Steigerung der Langzeitstabilität, was teilweise auf die Bildung von Mangancarbonat und dessen mögliche Blockierung aktiver Zentren zurückgeführt wurde. Zweitens wurde die Verwendung von Lösungsmitteln mit hohem Dipolmoment als Inhibitoren der Wasseradsorption am Katalysator untersucht. Dabei zeigte sich, dass die Anwesenheit bestimmter Flüssigkeiten das Kristallitwachstum während der CO2-Hydrierung reduzieren können. Stark adsorbierende Lösungsmittel führten nicht nur zu einer Stabilitätssteigerung, sondern auch zur partiellen Vergiftung des Katalysators. Ein Additivgemisch aus Propylencarbonat und Methanol vereinte die stabilisierenden und aktivitätsfördernden Effekte erfolgreich und führte zu erhöhter Methanolausbeute bei gleichzeitig verbesserter struktureller Stabilität des Katalysators im Langzeittest
Novel enabling technologies to support deployment of mobile robots in public spaces
No full textOngoing improvements in the field of robotics make it seem like having robots walk and drive around in public spaces is an inevitable future. However, because of their novel nature, there are neither precise laws nor guidelines on how to deploy a robot in a public setting. Because of the need for underlying data to aid in formulating these laws and guidelines, the rokit project [\cite{ronnau2024roboter}] aims to send robots into public spaces and survey the reactions. As part of this project, we planned, applied for, and carried out a field test with the SPOT walking robot. This paper will explain the technical and legal difficulties in deploying such a robot and how we overcome them, as well as give a short overview of the resulting data.
Recent developments and publicly available videos in the field of robotics make it seem to the public that robots walking and driving autonomously in public spaces in the future are inevitable. However, because of their novel nature, there is a gap in Germany with regard to regulatory and legal guidelines for deployment of robots in a public setting. In an effort to support current regulatory efforts with real data and practical experience, the rokit project deployed mobile robots in public spaces, with a focus on capturing and later analyzing the reactions of the passers-by. Therefore, a central activity of the project was the planning, execution, and analysis of human reactions to mobile robots in public spaces within field tests. This paper describes the technical and legal challenges encountered during the deployment planning and execution processes and the technical solutions that were developed in the form of a bespoke robotic payload to address them. Furthermore, this work provides a brief overview of the resulting data and provides an outlook for how others can successfully deploy mobile robots in public spaces
Plastic shrinkage and capillary pressure development of low-embodied CO2 mortars
No full textThis study aims to contribute to the understanding of the effects of SCMs on plastic shrinkage and capillary pore pressure, focusing on mortars made with partial replacement of Portland cement by metakaolin and limestone powder. Specifically, it investigates how different replacement rates of SCMs, combined with varying levels of workability achieved through adjustments in water content and superplasticizer dosage, influence these phenomena. The work also examines the broader implications of these two types of SCMs on some other early-age and long-term properties of the designed mortars. These include workability, heat evolution, phase formation (through thermodynamic modelling), structuring, and strength development.
The results demonstrate that partially replacing Portland with MK and LSP at any replacement level promotes plastic shrinkage in almost all of the cases considered.This is in contrast to what has been believed to be the case for these two types of SCMs. The data collected show that the promoted plastic shrinkage is a joint action of capillary pressure development along with workability, hydration kinetics, and structuring.
The study’s findings are expected to fill some gaps in the current literature, where the plastic shrinkage of materials containing metakaolin and limestone powder has been underexplored. By conducting detailed investigations into the role of these SCMs, alongside the use of statistical analyses, this research provides valuable insights into optimizing the performance of sustainable cementitious materials