Mémoire (M.Sc.T.)-- Université du Québec à Chicoutimi, 1992. / Bibliogr.: f. 70-77. Document électronique également accessible en format PDF. CaQCU

Thesis -- Departmental honors in Chemistry. / Bibliography: ℓ. 40-42.

Thesis (doctoral)--Technische Hochschule, Aachen, 2005.

Thesis (M.A. Sc.)--Centre for Building Studies, Concordia University, 1993. / Includes bibliographical references (leaves 88-93). Available also on the Internet.

This dissertation investigates the role of thermomechanical processes in the production of regolith on airless body surfaces. Thermally induced breakdown may provide a significant contribution to their surface evolution, by breaking down rocks and degrading craters. In Chapter 1, we use the traditional terrestrial methodology of evaluating the efficacy of this process by modeling the rate of surface temperature change (dT/dt) on various airless surfaces, using a damage threshold of 2 K/min. We find that the magnitude of dT/dt values is primarily controlled by sunrise/set durations on quickly rotating bodies, such as Vesta, and by distance to the sun on slowly rotating bodies, such as Mercury. The strongest rates of temperature change occur on slopes normal to the sun when a sunrise or sunset occurs, either naturally or because of daytime shadowing. We find, however, that high dT/dt values are not always correlated with high temperature gradients within the surface. This adds to the ambiguity of the poorly understood damage threshold, emphasizes the need further research on this topic that goes beyond the simple 2 K/min criterion. We further investigate this shortcoming in the terrestrial literature in Chapter two by modeling stresses induced by diurnal temperature variations at the mineral grain scale on these bodies. We find that the resulting stresses are controlled by mismatches in material properties between adjacent mineral grains. Peak stresses (on the order of 100s of MPa) are controlled by the coefficient of thermal expansion and Young's modulus of the mineral constituents, and the average stress within the microstructure is determined by relative volume of each mineral. Amplification of stresses occurs at surface-parallel boundaries between adjacent mineral grains and at the tips of pore spaces. We also find that microscopic spatial and temporal surface temperature gradients do not correlate with high stresses, making them inappropriate proxies for investigating microcrack propagation. Although these results provide strong evidence for the significance of thermomechanical processes, more work is needed to quantify crack propagation and rock breakdown rates in order to understand their overall contribution to surface evolution on these bodies. In Chapter 4, we investigate macroscopic scale effects on thermally induced stress fields in boulders of varying sizes and find that macroscopic thermal gradients may play a role in crack propagation within boulder interiors.

abstract: The occurrence of exogenic, meteoritic materials on the surface of any world presents opportunities to explore a variety of significant problems in the planetary sciences. In the case of Mars, meteorites found on its surface may help to 1) constrain atmospheric conditions during their time of arrival; 2) provide insights into possible variabilities in meteoroid type sampling between Mars and Earth space environments; 3) aid in our understanding of soil, dust, and sedimentary rock chemistry; 4) assist with the calibration of crater-age dating techniques; and 5) provide witness samples for chemical and mechanical weathering processes. The presence of reduced metallic iron in approximately 88 percent of meteorite falls renders the majority of meteorites particularly sensitive to oxidation by H2O interaction. This makes them excellent markers for H2O occurrence. Several large meteorites have been discovered at Gusev Crater and Meridiani Planum by the Mars Exploration Rovers (MERs). Significant morphologic characteristics interpretable as weathering features in the Meridiani suite of iron meteorites include a 1) large pit lined with delicate iron protrusions suggestive of inclusion removal by corrosive interaction; 2) differentially eroded kamacite and taenite lamellae on three of the meteorites, providing relative timing through cross-cutting relationships with deposition of 3) an iron oxide-rich dark coating; and 4) regmaglypted surfaces testifying to regions of minimal surface modification; with other regions in the same meteorites exhibiting 5) large-scale, cavernous weathering. Iron meteorites found by Mini-TES at both Meridiani Planum and Gusev Crater have prompted laboratory experiments designed to explore elements of reflectivity, dust cover, and potential oxide coatings on their surfaces in the thermal infrared using analog samples. Results show that dust thickness on an iron substrate need be only one tenth as great as that on a silicate rock to obscure its infrared signal. In addition, a database of thermal emission spectra for 46 meteorites was prepared to aid in the on-going detection and interpretation of these valuable rocks on Mars using Mini-TES instruments on both MER spacecraft. Applications to the asteroidal sciences are also relevant and intended for this database. / Dissertation/Thesis / Ph.D. Geological Sciences 2011

>Magister Scientiae - MSc / Energy production from coal comes with an environmental cost because of the toxic waste produced during coal combustion such as coal ash and brine which are potential water and soil pollutants. Coal ash and brine contain toxic elements which can leach and contaminate soils and ground water if not properly disposed. This study investigated the mobility of species in coal fly ash co-disposed with brine at Sasol Secunda power station in order to establish if the ash dam could act as a salt sink. The ash was dumped as a slurry with 5:1 brine/ash ratio and the dam was in operation for 20 years. It was hypothesized that the disposed Secunda fly ash was capable of leaching toxic metal elements into the surrounding soils and ground water and therefore could not be used as a long term sustainable salt sink. Weathered fly ash samples were collected along a 51 m depth core at the Secunda ash dam by drilling and sampling the ash at 1.5 m depth intervals. A fresh fly ash sample was collected from the hoppers in the ash collection system at the power station. Characterization of both Secunda fresh ash and Secunda weathered ash core samples was done using X-ray diffraction (XRD) for mineralogy, X-ray fluorescence (XRF) for chemical composition and scanning electron microscopy (SEM) for morphology. Analysis of extracted pore water and moisture content determination of Secunda fresh ash and Secunda weathered ash core samples was done in order to evaluate the physico-chemical properties of the fly ash. The chemical partitioning and mobility of metal species in the ash dam was evaluated using the sequential extraction procedure. The XRD spectra revealed quartz, mullite and calcite as the dominant mineral phases in the weathered Secunda ash core samples while Secunda fresh ash contained quartz, mullite and lime. The major oxides identified by XRF analysis for both Secunda fresh ash and Secunda weathered ash include: SiO₂, Al₂O₃, CaO, Fe₂O₃, MgO, Na₂O, TiO₂ and K₂O. The minor oxides identified for both Secunda fresh ash and Secunda weathered ash were P₂O₅, SO₃ and MnO. The trace elements identified for both Secunda fresh ash and Secunda weathered ash were As, Ba, Ce, Co, Nb, Ni, Pb, Rb, Sr, V, Y, Zr and Th. However, U was detected in some of the Secunda weathered ash samples but not in Secunda fresh ash. Both Secunda fresh ash and Secunda weathered ash was classified as class F based on the sum of the oxides of silicon, aluminium and iron by mass and the CaO content as reported by XRF analysis, and further classified as sialic and ferrocalsialic type highlighting the significant levels of Si, Al, Ca and Fe in the fly ash based on XRF analysis. The XRF analysis further showed that brine codisposal on the ash may have been responsible for the slight enrichment of some species such as Na, SO₄²⁻, Mg, K and V in the disposed Secunda weathered fly ash. However, there was no significant accumulation of these species in the disposed fly ash despite continuous addition of an estimated 117.65 billion litres of brine over the 20 year period that the dam existed. Furthermore, Secunda ash dam showed an overall total salt capture capacity of only -0.01 weight %, a strong indication that the ash dam was incapable of holding salts and would release elements to the environment over time. The scanning electron microscopy (SEM) analysis revealed spherical particles with smooth outer surfaces for Secunda fresh ash while Secunda ash core samples consisted of agglomerated, irregular particles appearing to be encrusted, etched and corroded showing that weathering and leaching had occurred in the ash dam. A decrease in pH, electrical conductivity (EC) and total dissolved solids (TDS) was observed in Secunda ash core samples compared to Secunda fresh ash. While Secunda fresh ash (n = 3) had a pH of 12.38 ± 0.15, EC value of 4.98 ± 0.03 mS/cm and TDS value of 2.68 ± 0.03 g/L, the pH of Secunda ash core (n = 35) was 10.04 ± 0.50, the EC value was 1.08 ± 0.14 mS/cm and the TDS value was 0.64 ± 0.08 g/L. The lower pH in the ash dam created an environment conducive to the release of species through leaching, while the lower EC and TDS in the ash dam implied the loss of ionic species from the ash which resulted from leaching. The moisture content (MC) analysis indicated that Secunda ash dam was very damp with an average MC of 54.2 ± 12.66 % for Secunda ash core creating favourable conditions for leaching of species in the ash dam while Secunda fresh ash had MC of 1.8 ± 0.11 %. The bottom of Secunda ash dam appeared water logged which could cause slumping of the dam. The sequential extraction procedure revealed that the major and trace elements contained in both Secunda fresh fly ash and Secunda weathered fly ash could leach upon exposure to different environmental conditions. The elements showed partitioning between five geochemical phases i.e. water soluble fraction, exchangeable fraction, carbonate fraction, Fe & Mn fraction and residual fraction. The labile phases consisted of the water soluble fraction, exchangeable fraction and carbonate fraction. The % leached out in the labile phases was expressed as a fraction of each element‟s total content e.g. Si (6.15 %) meant that 6.15 % of the total amount of Si in the ash was released in the labile phases. Na was the most labile among the major elements in the ash dam while Si and Al which form the major aluminosilicate ash matrix also showed significant lability. The % leached out in the labile phases for these major elements was as follows: for Secunda fresh ash: Si (6.15 %), Al (7.84 %), Na (11.31 %); for weathered Secunda ash core samples (n = 35): Si (7.53 %), Al (8.12 %), Na (11.63 %). This study showed that the fly ash generated at Sasol Secunda power station could not be used as a long term sustainable salt sink. The wet disposal method used at Sasol Secunda power station poses a high risk of groundwater contamination due to the high liquid to solid ratio used to transport the ash for disposal, which may lead to rapid dissolution of all the soluble components in the fly ash. The large volumes of brine that pass through Secunda ash dam in the wet ash handling system present a greater environmental concern than the dry ash handling system which involves small amounts of brine entering the ash dump.

This Masetr thesis looks into weathering pits of nature park Česká Kanada. The theoretical part of the thesis investigates research of weathering pits done in the Czech Republic as well as abroad. The practical part deals with weathering pit-bearing as well as weathering pitabsent blocks of rock within the study area. It describes their geological-geomorphological environment and attempts to find differences between the weathering pit-bearing and absent blocks (the presence of cracks, altitude, landforms, shape of the rock block and more). Furthermore it was established that a suitable rock block morphology (respectively the existence of horizontal plane) is important for formation of weathering pits. It also studies water properties in selected weathering pits, relationship of overhangs to prevailing wind directions. A correlation between overhang and wind direction was found in sense that NW to W winds correspond with overhang formation on eastern sides of weathering pits. Water in weathering pit of Čertův kámen located in sunny bare landscape shows significantly different properties in comparison with water properties of remaining weathering pits located in forrested areas.

Com a publicação e vigência da norma brasileira de desempenho NBR 15575:2013 amplia-se a necessidade de pesquisas que avaliem os fatores influentes sobre o desempenho dos materiais em função do local em que são empregados, principalmente no caso de materiais cimentícios, uma vez que, além de serem altamente utilizados no país, são severamente danificados por condições de umidade, radiações solares e variações de temperatura. Sendo assim, frente à exposição e função da argamassa de rejuntamento em sistemas de revestimento aderido, o material de preenchimento requer maior atenção principalmente porque o seu desempenho de forma isolada afeta no desempenho do sistema como um todo, seja do ponto de vista estético, de estanqueidade à água ou de segurança ao uso. Dessa forma, objetivando avaliar a influência do intemperismo sobre o desempenho de argamassas de rejuntamento à base de cimento Portland, essa pesquisa desenvolveu um plano experimental com 4 variáveis de influência, quais sejam: fabricante da argamassa (três níveis), cor da argamassa (branco, cinza e preto), tratamento superficial (sem tratamento, dois produtos hidrofugantes de bases diferentes) e tipo de exposição (referência, natural e artificial). A exposição ao intemperismo natural ocorreu na cidade de Porto Alegre durante 252 dias e a exposição artificial foi realizada em simulador ambiental do tipo radiação UVA e umidade por condensação durante 140 dias. Os resultados apontam para degradação física das argamassas do ponto de vista de alteração de cor e aumento da absorção de água das argamassas após intemperismo. A aplicação de produtos de proteção altera a cor das argamassas, sendo que o tratamento à base de metil siliconato de potássio causa manchas desuniformes em argamassas escuras e não apresentou melhorias quanto à absorção de água das argamassas de rejuntamento. O ensaio em câmara de intemperismo não foi capaz de reproduzir as degradações alcançadas no ambiente de Porto Alegre para as argamassas pretas. Por fim, todos fatores controláveis de forma isolada têm efeito significativo sobre as características cor, absorção de água e abrasão. Dessa forma, não é possível eleger uma argamassa que atenda de forma satisfatória a todas as propriedades avaliadas, demonstrando a ausência de requisitos em norma. / Since the Brazilian performance standard NBR 15575:2013 was published and entered into effect, the need for research that assesses the factors that influence the performance of materials as a function of the location where they are employed, has grown, especially in the case of cimenticious materials, given that these are not only frequently employed in the country, but also severely damaged by moisture, solar radiation and temperature variations. Because of the exposure and function of tile grout in coating systems, the filling material requires greater attention, mainly because its isolated performance affects the performance of the system as a whole from an aesthetic, water proofing or safety perspective. This research was therefore developed to evaluate the influence of weathering on the performance of grouts based on Portland cement using an experimental plan with 4 variables of influence, namely: the manufacturer of the grout (three levels), the color of the grout (white, gray and black), the surface treatment (without treatment, two water-repellent products with different bases) and type of exposure (reference, artificial and natural). The natural exposure to weather occurred in the city of Porto Alegre for 252 days and the artificial exposure was performed in an UVA radiation and moisture condensation environmental simulator for 140 days. The results point to the physical degradation of the grout regarding the change of color and an increase in water absorption of the grout after weathering. The application of protection products changes the color of the grouts, with the treatment based on Potassium Methyl Siliconate causing uneven staining in dark grouts without presenting improvements regarding the water absorption of the tile grout. The test in the weathering chamber wasn't able to reproduce the degradation reached in the environment of Porto Alegre for the black grouts. Finally, all controllable factors in isolation had a significant effect on the Color, Water Absorption and Abrasion characteristics. It's therefore not possible to point to a mortar that meets all assessed properties in a satisfactory manner, demonstrating the non-compliance with the requirements in the standard.

O trabalho buscou identificar se o intemperismo acelerado Xênon, utilizando a norma ASTM D4452-12, em corantes naturais encapsulados em matriz de sílica pelo processo sol gel com o uso de alcóxidos, conforme descrito pela patente INPI BR 10 2013 0219835, e injetadas em matriz de policloreto de polivinila (PVC) preservam as características de cor original dos corantes. Utilizou-se comparação dos mesmos corantes naturais – carmim, curcuma, índigo e urucum – sem encapsulamento e com encapsulamento, e injetados na mesma matriz de PVC. Executou-se a determinação da variação da cor antes do ensaio de intemperismo e após 126 h, 252 h, 378 h e 504 h em câmara de intemperismo Xênon utilizando-se a norma ASTM D4459-12. Utilizou-se o corante Tartrazina (INS 102) um azo corante sem encapsulamento como comparação do comportamento dos corantes naturais com um corante sintético. Os resultados indicam que não houve proteção da perda da coloração para os corantes naturais encapsulados, sendo a perda de coloração mais acentuada que os não encapsulados. Concluiu-se que é necessário executar alguns cuidados nas fases de encapsulamento dos corantes naturais como: uma dispersão cuidadosa dos corantes naturais e inclusão de um processo de repetição do encapsulamento do xerogel. / The study aimed to identify the Xenon accelerated weathering, using ASTM D4452-12 standards, of natural dyes encapsulated in the silica matrix by the sol-gel process with the use of alkoxides as described by the patent INPI BR 10 2013 0219835, and injected into matrix of polyvinyl chloride (PVC) preserve characteristics of original color of the dye. We used to compare the same natural colors - carmine, turmeric, indigo and annatto - without encapsulation and with encapsulation, and injected into the same matrix of PVC. Performed to determine the change in color before the weathering test after 126 h, 252 h, 378 h and 504 h in Xenon weathering chamber using ASTM D4459- 12 standards. We used the dye Tartrazine (INS 102) an azo dye without encapsulation as a comparison of the behavior of natural dyes with a synthetic dye. The results indicate that there was no protection of natural dyes encapsulated, with the loss of saturation more severe than the non-encapsulated natural dyes. It follows that some care needs to perform the encapsulation stages of natural dyes as a careful dispersion of natural colorants includes a process of repeat the encapsulation of the xerogel.