In den durchgeführten Versuchsreihen wurden die Wasserabsorption sowie die Gas- und Wasserpermeabilität sowohl an gerissenen als auch rissfreien Prüfkörpern aus textilbewehrtem Beton (TRC) untersucht. Eine deutliche Steigerung der Wasseraufnahme bei Proben mit unbeschichteten Textilien konnte mit Zunahme der Garnfeinheit beobachtet werden. Bei den gerissenen Proben besteht eine ausgeprägte Abhängigkeit der Transportraten von Flüssigkeiten und Gasen zu den relevanten Risscharakteristika (kumulative Risslänge, Rissbreite). Weiterhin sind Selbstheilungseffekte von feinen Rissen infolge einer zyklischen Wasserbeaufschlagung beobachtet worden. Hierbei kam es zu einer deutlichen Reduzierung der Transportraten sowohl für Wasser als auch für Gase. Eine speziell entwickelte Permeabilitätsmesskammer zur Durchführung von In- Situ-Messungen ermöglicht Untersuchungen zum Stofftransport unter axialer Zugbelastung bei verschiedenen Dehnungszuständen.

Spritzgießbare Duroplaste zeichnen sich durch hohe thermo-mechanische Beständigkeit, geringe Schwindung und niedrige Materialkosten aus. Damit können die Anforderungen an spritzgegossene Präzisionsbauteile für den Automobilbau erreicht werden. Im Rahmen der vorliegenden Arbeit werden unterschiedliche Novolak-Phenolformmassen hinsichtlich ihres hygroskopischen Verhaltens und dessen Auswirkung auf die Spritzgießverarbeitung und die Bauteilqualität untersucht. Das Absorptionsverhalten kann mithilfe der Fick’schen Diffusionsgesetzte näherungsweise beschrieben werden. Auf Basis von mechanischen Untersuchungen sowie der Beurteilung der Maßhaltigkeit eines Präzisionsdemonstrators hinsichtlich Schwindung und Verzug wird zudem der Einfluss der Prozessparameter beim Spritzgießen bestimmt. Die vorgestellten Untersuchungen zeigen die Grenzen der Verarbeitung und der realisierbaren Bauteilqualität auf, die auf die großserientaugliche Verarbeitung von duroplastischen Bauteilen übertragen werden können. / Injection moldable thermosetting materials show excellent material properties, e.g. high thermo-mechanical resistance and reduced shrinkage in combination with low material cost. Thus, technical requirements for high performance parts for automotive applications can be achieved. In the scope of this work different phenolic novolac compounds were investigated regarding their hygroscopic behavior with its influence for injection molding and product quality. The absorption can be approximately described by Fick’s-Diffusion-Model. The interrelationship of injection molding parameters and the thermo-mechanical behavior is examined on the basis of mechanical testing and the assessment of the dimensional accuracy for a thermoset high precision part. The presented investigations point to the limit of processing and realizable part quality which can be transferred for high performance parts molded in mass production.

Made available in DSpace on 2014-12-17T14:58:10Z (GMT). No. of bitstreams: 1 LucieneMR_DISSERT.pdf: 3721446 bytes, checksum: 16ced8820ae92014f7d8c365770f515c (MD5) Previous issue date: 2011-08-11 / In the present research work, composites were prepared using pine apple leaf fibres (PALF) as reinforcement with unsaturated polyester resin as matrix, incorporating with fire retardant at different compositions. The PALF was obtained from the decortication of pine apple leaves obtained from Ramada 4 from Ielmo Marinho in the State of Rio Grande do Norte. The unsaturated polyester resin and the catalyzer were bought from the local establishment. The fire retardant, aluminium tri-hydroxide - Al(OH)3 was donated by Alcoa Alum?nio S.A and was used in the proportions of 20%, 40% and 60% w/w. Initially the fibres were treated with 2% NaOH for 1 hour, to remove any impurities present on the fibre surface, such as wax, fat, pectin and pectate, in order to have a better adsorption of the fibres with the matrix as well as the flame retardant. The fibre mat was prepared in a mat preparator by immersion, developed in the Textile Engineering Laboratory, at the UFRN. The composites (300x300x3 mm) were prepared by compression molding and the samples (150x25x3 mm) for analysis of the properties were cut randomly using a laser cutter. Some of the cut samples were used to measure the smoke emission and fire resistance using UL94 standard. Mechanical tension-extension and flexural properties were carried in CTG?s RN and the Laborat?rio de Metais e Ensaios Mec?nicos Engenharia de Materiais UFRN , as well as SEM studies were carried out at N?cleo de Estudos em Petr?leo e G?s Natural - UFRN . From the observed results, it was noted that, there was no marked influence of the fire retardant on the mechanical properties. Also in the water absorption test, the quantity of water absorbed was less in the sample with higher concentration of fire retardant. It was also observed that the increase in the proportion of the fire retardant increased the time of burning, may be due to the compactness of the composite due to the presence of fire retardant as a filling material even though it was meant to reduce the rate of inflammability of the composite / Na presente pesquisa foram desenvolvidos comp?sitos com fibras da folha do abacaxizeiro (PALF - Pineapple Leaf Fiber), utilizando resina de poli?ster insaturado como matriz, incorporando retardante de chama em diferentes composi??es. As fibras da folha do abacaxizeiro foram obtidas na ramada 4 do munic?pio de Ielmo Marinho no Estado do Rio Grande do Norte. A resina de poli?ster insaturado e o catalisador foram comprados no com?rcio. O retardante de chama de alumina trihidratada (hidr?xido de alum?nio - Al(OH)3) foi doado pela empresa Alcoa Alum?nio S.A. e foi utilizado em propor??es de 20%, 40% e 60% do peso do material utilizado na fabrica??o dos comp?sitos. As PALFs foram tratadas com 2% de hidr?xido de s?dio, por 1 hora, para eliminar as impurezas superficiais tais como ceras, gorduras, pectinas e pectatos, para que houvesse uma melhor ades?o da matriz ?s fibras, bem como do retardante de chama. As mantas de fibras foram preparadas num preparador de manta por imers?o, desenvolvido no Laborat?rio de Engenharia T?xtil da UFRN. Os comp?sitos (300x300x3 mm) foram moldados por compress?o e as amostras (150x25x3 mm) para an?lise das propriedades foram cortadas, em diferentes posi??es da placa do comp?sito com aux?lio de uma m?quina de laser. As propriedades mec?nicas de tra??o e flex?o em tr?s pontos foram realizadas no CTG?s RN e no Laborat?rio de Metais e Ensaios Mec?nicos de Engenharia de Materiais da UFRN. Os testes da emiss?o de fuma?a e resist?ncia ao fogo foram realizados no Laborat?rio de Engenharia T?xtil da UFRN, utilizando a norma UL94. As amostras resultantes das propriedades mec?nicas foram avaliadas no MEV do N?cleo de Estudos em Petr?leo e G?s Natural da UFRN. Com base nas an?lises dos resultados nos ensaios mec?nicos, observou-se que o retardante de chama n?o tem influ?ncia significativa. Tamb?m observou-se que no ensaio de abosor??o de ?gua, quanto maior a concentra??o de retardante de chama, a quantidade de ?gua absorvida ? menor. No teste de inflamabilidade, observou-se que quanto maior a concentra??o de retardante de chama, maior o tempo de queima. Pode ser conclu?do que a presen?a de retardante de chama, al?m de atuar como inibidor de chama, tamb?m atua como uma carga que influ?ncia a compacta??o do comp?sito e desta forma reduz a taxa de queima

Abstract Wood is an essential material that has many applications in the fields of engineering and especially in the forest industry, which is particularly important in Fennoscandia. Among the various modification methods for wood, thermal modification has grown substantially over the past decades. It is an environmentally friendly method for increasing the lifetime and usability of timber. The aim of this thesis is to characterize the properties of thermally modified wood as well as to obtain new information on the changes taking place in pinewood due to the thermal modification process. Several NMR methods were used to gain information on the effect of thermal modification on the microstructure and moisture components of Pinus sylvestris pinewood. Pinewood samples thermally modified at different temperatures were studied and compared to corresponding unmodified wood samples. Diffusion of water and methane was studied using pulsed-field-gradient stimulated-echo measurements to determine the highly anisotropic size distribution of pores in different cell structures of pinewood. NMR cryoporometry and relaxometry measurements were conducted to gain information on the amounts and environments of both the bound and free water absorbed into the wood samples. Cryoporometry measurements resulted in an upper limit value for the size of bound water sites and the combination of cryoporometry and relaxometry data enabled the size determination of cell wall micropores. Magnetic resonance imaging was used to visualize the spatial distribution of absorbed free water in the studied samples. Together these methods give a broad overall picture of the effects of the modification process. The results of this work give new insight into the microstructure of thermally modified pinewood and its relationship to moisture, which is of importance for both wood science as well as industry. The applicability of the NMR techniques used here to the study of wood is also proven in this work. Using the techniques developed, it is possible to determine the optimal modification temperature, which is high enough to obtain the desired effects, but low enough not to destroy the microstructure of wood. / Tiivistelmä Puuta pystytään hyödyntämään useilla eri aloilla ja se on materiaalina tärkeä etenkin Fennoskandiassa merkittävälle metsäteollisuudelle. Useiden erilaisten puun käsittelymenetelmien joukossa lämpökäsittely on kasvattanut voimakkaasti suosiotaan viime vuosikymmeninä. Kyseessä on ympäristöystävällinen menetelmä, jolla voidaan pidentää puun käyttöikää sekä käytettävyyttä erilaisissa sovelluskohteissa. Tämän väitöskirjan päämääränä on ollut lämpökäsitellyn puun ominaisuuksien tutkiminen ja uuden tiedon saaminen puussa lämpökäsittelyprosessin myötä tapahtuvista muutoksista. Työssä käytettiin useita eri NMR-menetelmiä lämpökäsitellyn mäntypuun (Pinus sylvestris) mikrorakenteen sekä puussa olevan kosteuden aiheuttamien vaikutusten tutkimiseksi. Työssä tutkittiin eri lämpötiloissa käsiteltyjä mäntypuunäytteitä, joita verrattiin vastaaviin käsittelemättömiin näytteisiin. Veden ja metaanin diffuusiota tutkittiin PGSTE-menetelmällä puun erittäin anisotrooppisen solurakenteen sisältämien huokosten mittojen määrittämiseksi. NMR-kryoporometria- ja -relaksometriamittaukset antoivat tietoa puuhun imeytyneen sidotun ja vapaan veden määrästä ja esiintymisympäristöstä. Kryoporometria-mittausten tuloksista saatiin yläraja sidotun veden esiintymispaikkojen koolle, ja kryoporometria- ja relaksometriamittausten tuottaman tiedon yhdistäminen mahdollisti soluseinämien mikrohuokosten koon määrittämisen. Magneettikuvausta käytettiin näytteisiin absorboituneen veden avaruudellisen jakauman määrittämiseen. Käytetyt menetelmät tarjoavat laajan kokonaiskuvan lämpökäsittelyprosessin vaikutuksista puulle. Tämän työn tulokset antavat puutiedettä ja -teollisuutta hyödyttävää uutta tietoa lämpökäsitellyn männyn mikrorakenteesta sekä sen suhteesta kosteuteen. Väitöskirja myös osoittaa käytettyjen NMR-menetelmien soveltuvan hyvin puun tutkimiseen. Tämän tutkimuksen myötä kehitettyjen menetelmien avulla voidaan määrittää mm. optimaalinen lämpökäsittelylämpötila, joka on riittävän korkea haluttujen ominaisuuksien kannalta aiheuttamatta kuitenkaan puun mikrorakenteen hajoamista.

Forms of cavernous weathering - tafoni and honeycombs - belong to long-term investigated and discussed phenomena in geology. The reason for the difference in size between few centimetres- long honeycombs and the several-metres-long tafoni has not been yet studied. In my master thesis I compared the hydraulic properties of rocks with developed honeycombs and tafoni. The research consists of field measurements (measurement of suction pressures and capillary water absorption using Karsten tube) and laboratory measurements on tafoni and honeycomb samples (retention curve measurement, capillary water absorption, water vapour diffusion rate and saturated hydraulic conductivity). I have been studing honeycombs from various sites in the Bohemian Cretaceous Basin and tafoni from three different sites: Carbon Arkoses near Kralupy nad Vltavou, Cambrian Sandstone in Petra (Jordan) and Tunnel Spring Tuff in Crystal Peak (Utah). The measurements showed that values of suction pressure are far higher inside tafoni than inside honeycombs. This observation corresponds to different retention curves of studied rocks: steeper retention curve for honeycomb's quartz sandstone than for fine-grained arkosic sandstones to arkoses with tafoni. In the other part of my research I have compared the properties of hydrophobic...

The diploma thesis deals with measuring of infiltration by MiniDisk method and its evaluation, but also with analysis of intact and grab soil sample, by means of which it is possible to assess the soil quality. The measurements took place on 30.4.2019, 4.5.2019, 12.5.2019, 2.6.2019, 30.6.2019, 2.7.2019, 31.8.2019 and 21.9.2019 on grassland near the town of Luhačovice. Grab and intact soil samples were taken from the upper soil layer and processed in a pedological laboratory. The Zhang method was used to evaluate the infiltration results. The results of soil analyzes and infiltration were processed numerically, plotted and subsequently described and compared.

Water in porous rocks (e.g. sandstone) plays a fundamental role in their disintegration. However, the places where water enters the sandstone rocks are somewhat overlooked. At two sites in the Český ráj region, I use Karsten tube to measure capillary water absorption (CWA) of natural sandstone exposures and, using TDR (Time Domain Reflectometry) method, I study movement of water in a shallow zone of ruiniform sandstone landscape. The CWA differed up to four orders of magnitude at a distance of tens of meters, mostly depending on the type of the surface. The highest CWA was measured at highly weathered surfaces, the second most absorbent were less weathered surfaces covered with a biologically-initiated rock crust. The horizontal surfaces on the tops of the rock formations were even less absorbent, probably due to clogging by fine particles from soil. Surfaces covered with iron crust were the least absorbent. The differences between those surfaces are significant. After simulated infiltration, the maximum rate of the propagation of the wet front in the sandstone was from 5,5.10-6 do 1,9.10-4 m.s-1 measured by TDR. The water propagated at this rate only to a certain depth (the first tens of cm), but then the propagation stopped or slowed down rapidly. From a long-term measurement of volumetric...

In den durchgeführten Versuchsreihen wurden die Wasserabsorption sowie die Gas- und Wasserpermeabilität sowohl an gerissenen als auch rissfreien Prüfkörpern aus textilbewehrtem Beton (TRC) untersucht. Eine deutliche Steigerung der Wasseraufnahme bei Proben mit unbeschichteten Textilien konnte mit Zunahme der Garnfeinheit beobachtet werden. Bei den gerissenen Proben besteht eine ausgeprägte Abhängigkeit der Transportraten von Flüssigkeiten und Gasen zu den relevanten Risscharakteristika (kumulative Risslänge, Rissbreite). Weiterhin sind Selbstheilungseffekte von feinen Rissen infolge einer zyklischen Wasserbeaufschlagung beobachtet worden. Hierbei kam es zu einer deutlichen Reduzierung der Transportraten sowohl für Wasser als auch für Gase. Eine speziell entwickelte Permeabilitätsmesskammer zur Durchführung von In- Situ-Messungen ermöglicht Untersuchungen zum Stofftransport unter axialer Zugbelastung bei verschiedenen Dehnungszuständen.

Constitués de plusieurs composants (granulats naturels et pâte de ciment adhérente), les GBR ne sont à l’heure actuelle pas utilisés largement dans la formulation de nouveaux bétons. Les propriétés médiocres des GBR compliquent considérablement la détermination de la quantité d’eau efficace dans le béton frais. Tout d’abord, une étude bibliographique va mettre en évidence la grande dispersion des résultats des essais de caractérisation des GBR et des propriétés des bétons recyclés à l’état frais et durci. Ensuite, une étude vise à analyser l’hétérogénéité des GBR et des granulats de béton concassé (GBC) par rapport à différents paramètres : aux impuretés granulaires, à la densité et à la teneur en pâte de ciment, au malaxage du béton parent, et au niveau de la capacité d’absorption d’eau des GBC en fonction de leur état de pré-humidification. Enfin, une dernière partie est destinée à améliorer la maîtrise de l’eau efficace réelle dans la fabrication du béton recyclé. La cinétique d’absorption des GBC dans une pâte de ciment est tout d’abord étudiée. Ensuite, l’évolution de l’eau efficace durant le malaxage de bétons à base de GBC est investiguée au moyen d’une méthode originale basée sur le suivi des courbes de puissance du malaxeur. Finalement, l’effet d’un malaxage sous vide relatif sur les propriétés des bétons à base de granulats naturels et des bétons à base de GBC est étudié. / Composed of several components (natural aggregates and adherent cement paste), RCA are not widely recommended in new concrete formulations. Their poor properties considerably complicate the determination of the effective water in fresh concrete. In a first part, a bibliographic study will highlight the wide dispersion of the results of characterization tests of RCA and the properties of fresh and hardened recycled concrete. In a second part, the heterogeneity of RCA and crushed concrete aggregates (CCA) is studied according to different parameters: granular impurities, density, cement paste content, mixing of parent concrete, and water absorption capacity according to their pre-humidification. The third part consists of three experimental studies that intend to improve effective water control in the manufacture of recycled concrete. The absorption kinetics of CCA in a cement paste is first studied. Then, the evolution of effective water in fresh concrete during mixing is studied using an original method based on the power evolution of the mixer. Finally, the effect of vacuum mixing on the properties of ordinary and recycled concretes is investigated.

La tierra es uno de los materiales de construcción más antiguos que ha sido utilizado de diferentes maneras para proporcionar construcciones sociales, económicas y ambientales. La realidad en nuestro país no es ajena y se refleja en la cantidad de viviendas de tierra en las zonas rurales de la costa y sierra. No obstante, al evaluar su comportamiento frente a los fenómenos climáticos se ha constatado que estas viviendas han sufrido grandes estragos al estar expuestas a intensas lluvias, perdiendo su capacidad portante. Este escenario es una oportunidad para que nuevas investigaciones desarrollen técnicas alternativas con tierra. Entre ellas, la presente investigación aborda a los bloques de tierra comprimida (BTC), una versión moderna del adobe, estabilizados químicamente con cemento y fibras de bagazo de caña de azúcar. Para validar y comparar su comportamiento, se fabricaron los BTC y fueron sometidos a pruebas físicas y mecánicas en estado seco y saturado, además de ser evaluadas económicamente. La dosis de 4% de cemento y 0.75% de fibra de bagazo de caña tuvo el mejor desempeño de resistencia a la compresión y flexión en estado seco (2.31 y 0.66 Mpa respectivamente) como también en estado saturado (1.65 y 0.41 Mpa respectivamente), además de tener daños leves y una menor absorción de agua en las pruebas físicas. Por otro lado, se descubrió que al aumentar la cantidad de fibra a 1% en la mezcla suelo-cemento el comportamiento mecánico del BTC se mantenía estable y en algunos casos tiende a disminuir su resistencia, es decir que el porcentaje de fibra más óptimo en términos mecánicos y físicos para el BTC es de 0.75%. / Earth is one of the oldest building materials that has been used in different ways to provide social, economic and environmental constructions. The reality in our country is no different and is reflected in the number of earthen houses in the rural areas of the coast and highlands. However, when evaluating their behavior in the face of climatic phenomena, it has been found that these dwellings have suffered great damage when exposed to heavy rains, losing their load-bearing capacity. This scenario is an opportunity for new research to develop alternative earth techniques. Among them, the present research addresses compressed earth blocks (CEB), a modern version of adobe, chemically stabilized with cement and sugar cane bagasse fibers. To validate and compare their performance, BTCs were manufactured and subjected to physical and mechanical tests in dry and saturated states, as well as being economically evaluated. The dose of 4% cement and 0.75% bagasse fiber had the best compressive and flexural strength performance in dry state (2.31 and 0.66 Mpa respectively) as well as in saturated state (1.65 and 0.41 Mpa respectively), in addition to having slight damage and lower water absorption in the physical tests. On the other hand, it was found that by increasing the amount of fiber to 1% in the soil-cement mixture, the mechanical behavior of BTC remained stable and in some cases tended to decrease its strength, i.e. the most optimal percentage of fiber in mechanical and physical terms for BTC is 0.75%. / Tesis