Hoy en día existen diversas estructuras en la que se ha dado la aplicación del concreto liviano estructural, por lo que empresas contratistas apuestan por agregados livianos para fabricar concreto liviano de alta resistencia y que cumpla con sus requisitos de diseño. Estos estudios comenzaron a principios de la década de 1980, con óptimos resultados en 1992. Como resultado de todos estos aportes, la información de diseño se ha convertido al alcance de muchos profesionales, y ha permitido que el concreto liviano sea utilizado en alta resistencia y alta durabilidad (Hoff 1992). Es por ello mismo, que nuestra investigación propone el uso de un concreto liviano estructural con perlita de poliestireno expandido en un sistema de albañilería confinada. Este estudio comprende la elaboración del diseño de un concreto liviano estructural; en primer lugar, se investigó un rango apropiado de perlita ya que según Thanon y Jihad (2016) señalan que para obtener óptimos resultados en resistencia a compresión la dosificación de perlita debe variar entre un intervalo de 13-23% ,y es por ello mismo que se escoge trabajar con un porcentaje de 16 % de perlita de poliestireno expandido, pero para términos de comprobación en las propiedades térmicas, también se diseñó con 26% y 36% de perlita; en segundo lugar, para proceder a realizar el diseño del concreto se diseña en base a los requisitos mínimos que establece ACI 318 y con referencias en ACI 211R, la cual interviene en ciertos parámetros para obtener las características de un concreto liviano estructural. / Today there are various structures in which there has been the application of lightweight structural concrete, so contractor companies are committed to lightweight aggregates to manufacture lightweight, high strength concrete that meets its design requirements. These studies conducted in the early 1980s, with optimal results in 1992. As a result of all these contributions, design information has become available to many professionals, and has allowed light concrete to be used for new applications and novelties where high strength and high durability are desirable (Hoff 1992). That is why our research proposes the use of a lightweight structural concrete with expanded polystyrene bead in a confined masonry system for single-family homes. This study includes the development of the design of a lightweight structural concrete; First, a range of bead was investigated since according to Thanon and Jihad (2016) it was pointed out that to obtain optimum results in compressive strength the dosage of perlite must vary between a range of 13-23%, and that is why same that it is chosen to work with a percentage of 16% expanded polystyrene perlite, but for terms of checking the thermal properties, it is also designed with 26% and 36% perlite; secondly, to proceed with the design of the concrete, it is designed based on the minimum requirements established by ACI 318 and with references in ACI 211R, the quality of intervention in specific parameters to obtain the characteristics of a lightweight structural concrete. / Tesis

Regelflächen, das sind durch die Bewegung von Geraden erzeugte Flächen, haben für den Betonleichtbau unter den Gesichtspunkten Statik und Herstellung herausragende Eigenschaften: Auch wenn sie doppelt gekrümmt sind, können sie geradlinig bewehrt oder vorgespannt werden. Außerdem kann die Schalung beispielsweise durch Heißdrahtschneiden aus Polystyrol-Hartschaum gewonnen werden. In gängigen CAD-Systemen ist die Klasse der Regelflächen bislang nicht angemessen repräsentiert und steht deshalb für die Bauteilgestaltung nur eingeschränkt zur Verfügung. Liniengeometrie für den Leichtbau liefert nun ein mathematisches Modell, das Regelflächen und auf sie wirkende Kräfte abbildet, und entwickelt daraus Formfindungswerkzeuge, die in einer vertrauten Entwurfsumgebung das Prinzip form follows force unterstützen. [Aus. Einführung] / Ruled surfaces, which are surfaces created by the movement of straight lines, have outstanding properties for lightweight concrete construction from the viewpoints of statics and production: even if they are double-curved, they can be reinforced or prestressed in a rectilinear fashion. In addition, the formwork can be obtained ef ciently from rigid polystyrene foam by hot wire cutting, for example. In current CAD systems, the class of ruled surfaces has not yet been adequately implemented and is therefore only available to a limited extent for component design. This project Line Geometry for Lightweight Structures provides a mathematical model that represents ruled surfaces and the forces acting on them, and uses this to develop form finding tools that support the principle of form follows force in a familiar design environment. [Off: Introduction]

Betondecken sind materialintensive Biegetragwerke, wenn sie, wie derzeit üblich, eben und aus einer Betonsorte hergestellt werden. Die Materialien sind dadurch nur an wenigen Stellen maximal und effizient ausgenutzt. Die vorliegende Dissertation greift ein daraus resultierendes Optimierungspotential auf. Eine verbesserte Ausnutzung der Baustoffe Beton und Stahl gelingt durch einen dreischichtigen Querschnittsaufbau. Dabei nehmen die beiden äußeren Betonschichten mit der eingebrachten Stahlbewehrung vor allem die Beanspruchungen aus Biegung und die Kernschicht aus Schub auf. Als Kernschichtmaterial kommen dabei Leichtbetone zur Anwendung. Der Fokus liegt auf der Untersuchung von schlaff bewehrten, einachsig gespannten, einfeldrigen Flachdecken des gewöhnlichen Wohnungs- und Bürobaus. In der Arbeit wird ein Überblick über den aktuellen Entwicklungsstand und die bereits vorliegenden Forschungsarbeiten zu geschichteten, sandwichartigen Betondecken gegeben. Sie geht auf die Eigenschaften von Beton, Stahl und Stahlbeton und ausführlich auf den Verbund zwischen Betonschichten ein, der die Tragfähigkeit geschichteter Betondecken besonders beeinflusst. Anschließend werden verschiedene Bauteilzustände erläutert und die Versagensarten, die bei geschichteten Elementen auftreten können, vorgestellt. Dazu gehören maßgeblich das Biegezug- und Biegedruckversagen sowie das Biegeschub- und Fugenversagen. Es werden sowohl Formeln zur Berechnung von Durchbiegungen im Gebrauchszustand als auch von Bruchlasten in Abhängigkeit der Versagensart bereitgestellt. Auch sind Rechenansätze zur Beurteilung des Bauteilzustandes infolge des unterschiedlichen Schwindens der Betone aufgeführt.

Les bétons légers, formés des fibres de bois et d’une pâte de ciment Portland, constituent une nouvelle alternative à explorer pour réduire l’impact environnemental des bâtiments. Ils sont utilisés dans la construction durable, comme des éléments secondaires, pour leurs performances thermiques, hydriques et mécaniques. Cependant, la généralisation de leur utilisation dans le bâtiment ne sera rendue possible sans résoudre certains verrous scientifiques liés à leur caractérisation et à leur formulation. Le présent travail s’inscrit dans cet objectif. Il s’agit de contribuer à la caractérisation de ces bétons légers à base des fibres de bois à travers l’expérience et la modélisation. Le module d’Young et la résistance à la rupture ont été mesurés par des tests de flexion et de compression. Un modèle numérique a été également développé pour prédire le comportement des éprouvettes en flexion et la réponse structurale des systèmes de coffrage permanent. La méthodologie numérique permet ainsi d’aider dans le choix des paramètres optimums pour une meilleure conception des panneaux de coffrage destinés à la construction. L’étude du comportement hygrothermique du matériau de construction bois-ciment a été abordée en s’appuyant sur l’expérience et la simulation. Les équations des transferts couplés de chaleur et d’humidité d’un milieu poreux ont été implémentées dans le logiciel Comsol Multiphysics®. En dernier, le modèle développé a été appliqué et validé sur plusieurs réponses dynamiques issues des tests hygrothermiques réalisés en interne. Les mesures des propriétés physico-thermique du matériau composite bois-ciment ont été ensuite intégrées dans le code Abaqus via une routine utilisateur Umatht dans l’objectif de simuler le comportement thermique à hautes températures des panneaux composites bois-ciment. Les profils des températures sont évalués et comparés à ceux des tests de carbonisation réalisés, à l’aide d’un panneau rayonnant, sur des échantillons exposés à un flux de chaleur uniforme de 6kW/m2. Les simulations montrent que le modèle développé est capable de prédire les profils de températures, la zone et la profondeur de la couche du charbon durant l’exposition au feu / Lightweight concretes made from wood fibres and Portland cement paste are a new alternative for the reduction of the environmental impact of buildings. They are used in sustainable constructions as secondary elements for their thermal, hydric and mechanical performance. However, the generalisation of their use is not possible without resolving certain scientific obstacles related to their characterisation. Hence the aim of the present work, which is to contribute towards their characterisation through experimentation and numerical simulation. The Young's modulus and tensile strength were measured through flexural and compression tests. A numerical model has also been developed to predict the behaviour of specimens under bending test as well as their structural response when used as permanent formwork. In particular, the model helps to choose the optimum parameters for a better design of the formwork system. The study of the hygrothermal behaviour of the wood-cement material was carried out using both experimental work and simulation. The equations of coupled heat and moisture transfers for a porous medium have been implemented in the Comsol Multiphysics® software. The developed model has been applied and validated on several dynamic responses resulting from hygro-thermal tests carried out in the laboratory. The obtained physico-thermal properties of the wood-cement composite material were then incorporated into the Abaqus code via a Umatht user subroutine to simulate its high temperature behavior. The temperature profiles are evaluated and compared with the charring tests performed using a radiant panel on samples exposed to a uniform heat flux of 6kW/m². The simulations show that the developed model is able to predict the temperature profiles, the area and the depth of the charred layer during fire exposure

O estudo do comportamento de estruturas em situação de incêndio tem se tornado cada vez mais importante devido às graves consequências de incêndios que têm ocorrido no Brasil e em outros países. Por esse motivo, este trabalho tem como objetivo estudar o comportamento residual do concreto com pérolas de EPS sob altas temperaturas, pois se pretende utilizar esse concreto em painéis e em lajes pré-moldadas para a construção de edifícios de pequeno e de médio porte, por ele ser um concreto muito leve, com massa específica em torno de 1170 kg/m3, um pouco menos da metade da relativa ao concreto convencional. Para este estudo, foram utilizados corpos de prova cilíndricos e prismáticos, seguindo recomendações nacionais e internacionais. As análises foram realizadas para 200ºC, 400ºC e 600ºC, e foram avaliadas: massa específica, resistência à compressão, módulo de elasticidade estático, módulo de elasticidade dinâmico, resistência à tração por compressão diametral, resistência à tração na flexão e fator de tenacidade. Para esses dois últimos, foram utilizadas fibras de aço nas seguintes taxas: 0,3%, 0,6% e 0,9%. Os resultados foram comparados com os de concreto com EPS em temperatura ambiente e com os de concreto convencional, que já tem alguns resultados disponíveis na literatura técnica. Também foi realizada uma análise térmica numérica, utilizando o software ABAQUS 14, para calibrar duas propriedades: calor específico e condutividade térmica. Para isso, foram utilizados resultados obtidos na análise experimental. Os resultados numéricos e experimentais foram coerentes com os esperados. Os experimentais apresentaram redução de valor à medida que a temperatura aumentava, e comportamento pior em comparação ao concreto convencional. A adição de fibras aumentou a resistência à tração na flexão e também a tenacidade, tanto em temperatura ambiente quanto em temperaturas elevadas. / The study of the structures behavior in fire has become increasingly important due to the serious consequences of fires that have occurred in Brazil and in other countries. Therefore, this work aims to study the residual behavior of concrete with EPS beads under high temperatures, because it is intended to use it in panels and precast slabs for the construction of small and medium-sized buildings, for it is a very light concrete, with a density around 1170 kg/m3, slightly less than half that of conventional concrete. For this study, cylindrical and prismatic specimens were used, following national and international standards. The analyses were carried out to 200°C, 400°C and 600°C, and were evaluated: density, compression strength, static modulus of elasticity, dynamic modulus of elasticity, splitting tensile strength, flexural tensile strength, and toughness factor. For the latter two, steel fibers were used at the following rates: 0.3%, 0.6% and 0.9%. The results were compared with those of concrete with EPS at room temperature, and with conventional concrete which already has some results available in the technical literature. A numerical thermal analysis was also performed, using ABAQUS 14 software, to calibrate two properties: specific heat and thermal conductivity. For this, results obtained in the experimental analysis were used. The numerical and experimental results were consistent with those expected. The experimental results showed reduction of value as temperature increased, and worst behavior in comparison to ordinary concrete. The addition of fibers increased tensile strength in bending and also the toughness, both at room temperature and at elevated temperatures.

O estudo do comportamento de estruturas em situação de incêndio tem se tornado cada vez mais importante devido às graves consequências de incêndios que têm ocorrido no Brasil e em outros países. Por esse motivo, este trabalho tem como objetivo estudar o comportamento residual do concreto com pérolas de EPS sob altas temperaturas, pois se pretende utilizar esse concreto em painéis e em lajes pré-moldadas para a construção de edifícios de pequeno e de médio porte, por ele ser um concreto muito leve, com massa específica em torno de 1170 kg/m3, um pouco menos da metade da relativa ao concreto convencional. Para este estudo, foram utilizados corpos de prova cilíndricos e prismáticos, seguindo recomendações nacionais e internacionais. As análises foram realizadas para 200ºC, 400ºC e 600ºC, e foram avaliadas: massa específica, resistência à compressão, módulo de elasticidade estático, módulo de elasticidade dinâmico, resistência à tração por compressão diametral, resistência à tração na flexão e fator de tenacidade. Para esses dois últimos, foram utilizadas fibras de aço nas seguintes taxas: 0,3%, 0,6% e 0,9%. Os resultados foram comparados com os de concreto com EPS em temperatura ambiente e com os de concreto convencional, que já tem alguns resultados disponíveis na literatura técnica. Também foi realizada uma análise térmica numérica, utilizando o software ABAQUS 14, para calibrar duas propriedades: calor específico e condutividade térmica. Para isso, foram utilizados resultados obtidos na análise experimental. Os resultados numéricos e experimentais foram coerentes com os esperados. Os experimentais apresentaram redução de valor à medida que a temperatura aumentava, e comportamento pior em comparação ao concreto convencional. A adição de fibras aumentou a resistência à tração na flexão e também a tenacidade, tanto em temperatura ambiente quanto em temperaturas elevadas. / The study of the structures behavior in fire has become increasingly important due to the serious consequences of fires that have occurred in Brazil and in other countries. Therefore, this work aims to study the residual behavior of concrete with EPS beads under high temperatures, because it is intended to use it in panels and precast slabs for the construction of small and medium-sized buildings, for it is a very light concrete, with a density around 1170 kg/m3, slightly less than half that of conventional concrete. For this study, cylindrical and prismatic specimens were used, following national and international standards. The analyses were carried out to 200°C, 400°C and 600°C, and were evaluated: density, compression strength, static modulus of elasticity, dynamic modulus of elasticity, splitting tensile strength, flexural tensile strength, and toughness factor. For the latter two, steel fibers were used at the following rates: 0.3%, 0.6% and 0.9%. The results were compared with those of concrete with EPS at room temperature, and with conventional concrete which already has some results available in the technical literature. A numerical thermal analysis was also performed, using ABAQUS 14 software, to calibrate two properties: specific heat and thermal conductivity. For this, results obtained in the experimental analysis were used. The numerical and experimental results were consistent with those expected. The experimental results showed reduction of value as temperature increased, and worst behavior in comparison to ordinary concrete. The addition of fibers increased tensile strength in bending and also the toughness, both at room temperature and at elevated temperatures.

Im Zentrum der vorliegenden Arbeit steht ein zementgebundener Leichtbeton auf der Basis von aus Altpapier herausgelösten Cellulosefasern; hierfür wird im Folgenden die Bezeichnung CFLC (Cellulose-Fibre Lightweight Concrete) verwendet. Die Intention zur Untersuchung dieses mitunter auch als Papercrete bezeichneten und bislang nur verhältnismäßig wenig erforschten Materials beruht insbesondere darauf, dass von einer Kombination eines leicht verfügbaren pflanzlichen Faserstoffs mit einem mineralischen Bindemittel eine Reihe positiver Wechselwirkungen erwartet werden darf. Am Anfang stehen Erläuterungen zur Spezifik dieses Materials und eine Einordnung in den Kontext der üblichen Leicht- und Faserbetone. Nach einer Darstellung und Diskussion der bisher vorhandenen Erkenntnisse erfolgt eine Präzisierung der Aufgabenstellung. Anschließend werden die Besonderheiten von aus Altpapier herausgelösten Cellulosefasern vorgestellt und die charakteristischen Eigenschaften dieser Fasern beschrieben. Es folgen weiterhin Betrachtungen zur Problematik des Faseraufschlusses. In diesem Zusammenhang werden Wege aufgezeigt, wie dieser Prozess in betontechnologischer Hinsicht labor- und großtechnisch umgesetzt werden kann. Im Hinblick auf den Mischungsentwurf erfolgt eine Vorstellung von Methoden zur Bestimmung der für die Stoffraumrechnung relevanten Faserkennwerte. In einem weiteren Schritt werden die Methodik und der entwickelte Algorithmus für einen zielgerichteten Mischungsentwurf erläutert sowie eine Variante zur technologischen Klassifizierung von CFLC-Grundtypen vorgestellt. Nach Betrachtungen zur Auswirkung einer Cellulosefaserzugabe auf die Frisch- und Festbetoneigenschaften wird eine auf die Trockenrohdichte hin ausgerichtete Rezepturentwicklung anhand eines Beispiels demonstriert. Im Folgenden werden die Ergebnisse der umfangreichen Untersuchungen hinsichtlich der durch die Faserzugabe deutlich veränderten Frischbetoneigenschaften des CFLC sowie die Auswirkungen auf den Mischvorgang und die Einbautechnologie erläutert. Diesbezüglich erfolgt auch eine Darstellung der Erkenntnisse, die bei großtechnischen Versuchen mit dem CFLC in zwei Betonwerken gewonnen wurden. Des Weiteren werden die Ergebnisse aufgezeigt, die während begleitender Untersuchungen zum Erhärtungs- und Trocknungsprozess erzielt wurden. Dabei werden die strukturellen Auswirkungen der Hydratation des Zementes und der Trocknung beschrieben sowie die Aspekte erörtert, die im Zusammenhang mit der durch die Cellulosefaserzugabe verbundenen Erhärtungsverzögerung und den möglichen Gegenmaßnahmen stehen. Weiterhin werden auch Betrachtungen zur Effektivität einer Festigkeitssteigerung durch die Zugabe von Mikrosilika sowie zu den mit dem Trocknungsprozess einhergehenden Schwindverkürzungen durchgeführt. Schließlich erfolgt eine Darstellung der bei den Untersuchungen zu den Festbetoneigenschaften gewonnenen Erkenntnisse. Dabei werden die wesentlichsten mechanischen Kennwerte sowie das hygrische und wärmetechnische Verhalten unter Einbeziehung von Porositätskennwerten beleuchtet. Weiterhin erfolgt eine Beurteilung der Dauerhaftigkeit auf der Basis von Zeitraffer- und Auslagerungsversuchen. Das durch die Anwesenheit von Cellulose bestehende Risiko gegenüber einem biologischen Angriff wird dabei durch die Übertragung eines für Holzwerkstoffe üblichen Verfahrens bewertet. Einen wesentlichen Bestandteil dieser Arbeit stellen die bruchmechanischen Untersuchungen am CFLC dar. Nach einer Darstellung der verwendeten Ansätze und Kennwerte werden Überlegungen zur modellhaften Beschreibung des Verformungs- und Rissverhaltens erläutert. Weiterhin werden Möglichkeiten der optischen Erfassung von Bruchprozessen bzw. der mikroskopischen Untersuchung von Bruchflächen dargelegt. Dabei werden geeignete Wege zur Bestimmung geometrischer Kennwerte aufgezeigt. Das Versuchsprogramm zu den bruchmechanischen Untersuchungen konzentriert sich auf haufwerksporige CFLC-Zusammensetzungen im Bereich des Infraleichtbetons. Um eine Einordnung der ermittelten Ergebnisse vornehmen zu können, erfolgt die Einbeziehung von Porenbeton aus einem vergleichbaren Rohdichtebereich. Die gewonnenen Erkenntnisse basieren schwerpunktmäßig auf einaxialen Zugversuchen; mit in die Betrachtungen einbezogen werden allerdings auch Ergebnisse, die bei parallel durchgeführten Biege- und Druckversuchen gewonnen wurden. Zur Erfassung des Verformungs- und Bruchverhaltens des CFLC wird ein Ansatz auf der Basis des klassischen Wachstumsmodells formuliert. Auf der Grundlage der experimentellen Untersuchungen erfolgt letztlich eine Charakterisierung des Materialverhaltens durch die Beschreibung des typischen Kurvenverlaufs (Masterkurve). Darüber hinaus werden Betrachtungen zur Korrelation zwischen den bruchmechanischen Kennwerten und den geometrischen Texturkennwerten der Bruchflächen angestellt. Die anschließende Diskussion über die Ursachen der Strukturänderungen und den Rissbildungsprozess erfolgt unter Einbeziehung eines modellhaften Ansatzes zur Beschreibung der inneren Kontaktfläche zwischen den CFLC-Partikeln bei einer haufwerksporigen Situation. Das enorme Wasserspeichervermögen der Cellulosefasern hat zur Folge, dass die CFLC-Zusammensetzungen von jenem Wasseranteil dominiert werden, welcher für den Faseraufschluss benötigt wird. Eine Steigerung des Cellulosefaseranteils im Gesamtgemisch hat somit automatisch einen Anstieg der Porosität des trockenen Materials zur Folge, wodurch die ausgeprägte Abhängigkeit fast aller Kennwerte vom Cellulosefaseranteil resultiert. Hinsichtlich der mechanischen Eigenschaften wurde festgestellt, dass der Bewehrungseffekt der Fasern nicht in der Lage ist, die Festigkeitseinbußen infolge des Ansteigens der Porosität zu kompensieren. Eine Cellulosefaserzugabe hat aber generell eine positive Auswirkung auf die Duktilität und bewirkt zudem die Entstehung einer nennenswerten Tragfähigkeit nach einer begonnenen Makrorissbildung. / The present work addresses a cement-bound lightweight concrete incorporating cellulose fibres extracted from waste paper; use is hereinafter made of the acronym CFLC (cellulose-fibre lightweight concrete) to describe the resultant product. The main case for investigating this, as yet, comparatively under-researched material, also commonly referred to as “papercrete”, is that the act of combining readily available fibrous plant material with a mineral binding agent can be expected to yield a number of positive interactions. The first step involves elucidating the material’s specific characteristics and contrasting it with other lightweight, fibre-based concretes. Following exposition and discussion of insights arrived at in past studies, the precise nature of the task in hand is defined. The distinguishing features and characteristic properties of cellulose fibres extracted from waste paper are then set out and this is followed by a number of observations on the problems involved in pulping such fibres. Means of implementing the process both in the laboratory and during the full-scale engineering of concrete are also pointed up here. Methods of determining those fibre characteristics that are of relevance to the material volume calculation to be performed in respect of the mix design are similarly presented. In a further step, the methodology adopted and algorithm developed for a target-responsive mix design are elucidated and a system for the technological classification of basic types of CFLC is presented. Following deliberation on how adding cellulose fibres affects the properties of fresh and hardened concrete, a formulation geared towards a specific dry bulk density is demonstrated citing an illustrative example. Thereafter, the results of exhaustive studies regarding the significant changes to the properties of fresh CFLC brought about by adding fibres and the implications these have for the mixing process and placing technology are explained. The findings arrived at during full-scale trials with CFLC in two concrete works are also set out in this context. Likewise detailed are the results gained from accompanying studies of the hardening and drying process. The section provides a description of the structural consequences of hydrating and drying cement before addressing aspects with a bearing on the delay in hardening brought about by adding cellulose fibres as well as on potential countermeasures. There is also analysis here of whether adding microsilica occasions any increase in mechanical strength, consideration similarly being given to levels of shortening through shrinkage during the drying process. The work concludes by setting out the findings arrived at when studying the properties of the hardened concrete. Light is shed on the material’s key mechanical characteristics as well as on its hygric and thermic behaviour inclusive of porosity characteristics. Time-lapse and precipitation tests are then run to assess its durability. The risk of biological attack arising from the presence of cellulose is gauged adopting a standard procedure for timber materials. Mechanical fracturing tests conducted on CFLC are a key constituent of this study. Following delineation of the approaches and characteristics adopted, consideration is given to depicting deformation and crack behaviour in model form. Means of recording fracture processes optically or of subjecting fracture faces to microscopic examination are additionally aired, in the process pointing up suitable ways of determining geometric characteristics. The fracture test programme focuses on no-fines CFLC compositions in the range of infra-lightweight concrete. With a view to contextualising the results obtained, testing is extended to cover autoclaved aerated concrete with a comparable bulk density range. The findings arrived at derive primarily from uniaxial tensile-strength tests, though results gained from bending and compression tests run in tandem are likewise factored into appraisals. An approach based on the conventional growth model is formulated for the purpose of establishing the deformation and fracture behaviour of CFLC. Drawing on experimental studies, finally, the material’s behaviour is characterised by describing its typical curve pattern (master curve). Consideration is additionally given to the correlation between the fracture characteristics and geometric texture characteristics of fracture faces. The ensuing discussion of what causes the structural changes as well as of the crack-formation process is conducted adopting a model-based means of describing the inner contact faces between CFLC particles under no-fines conditions. The enormous propensity of cellulose fibres for storing water results in CFLC compositions being dominated by the water fraction required to pulp them. Increasing the fraction of cellulose fibres in the total mix thus automatically causes the porosity of the dry material to rise, which in turn explains the pronounced dependence of almost all characteristics on the proportion of cellulose fibres in the mix. Having regard to the material’s mechanical properties, it was ascertained that the fibres’ reinforcing moment was insufficient to compensate for losses of strength due to the increase in porosity. Adding cellulose fibres nevertheless has a positive impact on ductility whilst also being conducive to a noteworthy capacity for bearing loads following the onset of macrocracking.

The diploma thesis deals with the determination of the influence of size, shape and type of test specimen on values of modulus of elasticity of light-weight concrete. A lot of different specimens were prepared from two concrete’s mixtures for the experiment. Tests for measurement of static modulus of elasticity and dynamic modulus of elasticity by ultrasonic impulse velocity method were made. The results were assessed and summarized in tabular and graphical form.

Diploma thesis gives an overview of artificial lightweight aggregates based on fly ash. Fly ash such as the residues of coal burning is currently one of the most used secondary raw materials for new building materials for research papers. The results shows that the secondary energy products are not just fully substitute the primary component, but in many cases improves the final properties of building products. Wide complex of fly ashes not only from domestic sources was tested and it`s main properties important for it`s further application was determined. Laboratory production of artificial aggregates based on fly ash made by sintering and also by cold bonding and following manufacture of artificial fly ash aggregates in technological conditions are also solved. The thesis is simultaneously concentrate on review of the suitability of fly ash aggregates in lightweight concrete.It was found that the highest quality fly ash for the production of sintered fly ash aggregate is fly ash and FBC ash is the best for the production of cold bonded aggregates. It was also verified that both types of aggregates are applicable to lightweight concrete class LC 20/22. The vast majority of manufactured aggregates is suitable for the production of lightweight concrete class LC 30/33. It was demonstrated that the sintered fly ash aggregates can be also used for high strength lightweight concrete class LC 50/55. Tests have also verified that all tested fly ashes and products produced from them meet the requirements of legislation on environment.

Specified topic of the thesis is a multilevel evaluation of brittleness of selected building composites. The work deals with the opinions of fracture parameters of test specimens of lightweight and ordinary concrete. Specimens further differed fibres content in concrete mixtures, their type and length. The work is divided into two parts, theoretical and practical. The theoretical part conceives composite materials and introduction to fracture mechanics. The practical part describes the different steps for fracture-mechanical parameters evaluation using StiCrack and Excel Visual Basic software. The main part of the work is to evaluate the brittleness of different test specimens, taking into account the type of concrete mix and type of fibres.