The factors which affect the engineering properties of calcium carbonate cemented soil are examined. The influence of calcium carbonate content, molding moisture content, and confining pressure on the strength characteristics of two types of soil is investigated in two distinct phases of the research. Type A soil, obtained from the University of Arizona Campbell Avenue Farm in Tucson, was used for the artificially cemented specimen stage. It is composed of sand and silt-size particles with some clay and is virtually free of calcium carbonate in its natural state. Sierrita soil, obtained from the Twin Buttes Open Pit Mine south of Tucson, was used for the reconstituted sample stage. It is naturally cemented with calcium carbonate and is composed mainly of sand, gravel, a small amount of silt, and occasional large-sized (boulder and cobble) particles. Specimens for triaxial compression testing were compacted for each phase of the study under carefully controlled conditions. Three test series were carried out on Type A soil artificially cemented with calcium carbonate. Three percentages (0%, 15%, and 30%) on a dry weight basis of the soil were used. Two molding water contents, one dry and one wet of optimum moisture content, were established for each test series. Unconsolidated undrained triaxial compression tests were carried out on oven-dried specimens at three different confining pressures to obtain shear strength parameters. The fabric characteristics of selected specimens were then defined by viewing them under a scanning electron microscope. The results indicate that the strength of the calcium carbonate cemented soil depends on the distribution and not necessarily the content of the cementing agent within the soil mass. Visual examination of the various microstructures of the artificially cemented soil confirmed the hypothesis that strength gain occurs when the calcium carbonate particles are concentrated at the points of contact between soil grains. Visual examination of the fabric of the naturally cemented Sierrita soil showed the microstructure to be highly compressed with weathered calcium carbonate particles dominating the soil structure. The calcium carbonate content was found to range from 14 to 23%. Because of sampling difficulties, an in situ cohesion value for the Sierrita soil could not be obtained from conventional laboratory tests. Therefore, the value was obtained by back analysis of the stability of actual slopes existing at Twin Buttes Mine. Slope stability analyses using Bishop's Modified Method with a search routine based on the Simplex Method of Nelder and Mead were performed. Stability analyses were also performed using strength properties of artificially cemented Type A soil. These analyses showed the relationships among cohesion, friction angle, safety factor, and calcium carbonate content for a specified slope geometry.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Des nouvelles voies de synthèse sont proposées pour la préparation des hydroxyuréthanes et polyhydroxyuréthanes glycériliques, sans isocyanate, à partir de composés biosourcés fournisseurs de groupements cyclocarbonates hautement réactifs vis-à-vis des amines, diamines, polyamines. Les fournisseurs de groupement cyclocarbonate sont le carbonate de glycérol et le nouveau synthoon bifonctionnel l’acrylate de carbonate de glycérol. Des hydroxyuréthanes ou polyhydroxyuréthanes glycéryliques polyoxygénés et polyazotés ont été ainsi élaborés via ces nouveaux intermédiaires cyclocarbonates glycériliques en substitution des carbonates cycliques d’origine fossile comme les carbonates d’alkylènes. La stratégie d’élaboration des polyhydroxyuréthanes glycériliques à haut poids moléculaire s’appuie sur la réactivité séquencée de l’acrylate de carbonate de glycérol : réaction d’Aza-Michaël sur le groupement éthylénique de l’acrylate et réaction d’aminolyse par ouverture de cycles carbonates à 5- chaînons. Selon la nature des polyamines, on prépare des polymères de poids moléculaire supérieur à 40000 g/mol, d’aspects gel, mousse ou résine selon que les pontages linéaires ou interchaînes prédominent. Des réseaux chimiques intramoléculaires sont constitués par l’établissement des liaisons hydrogène entre les sites O-H ou N-H et l’oxygène du groupement carbamoyle du squelette glycérilique avec comme conséquence la réduction de la susceptibilité du groupe carbamoyle à l’hydrolyse et l’amélioration des propriétés de résistance chimique et mécanique des polyhydroxyuréthanes glycériliques. / New synthesis routes have been developed for the preparation of glycerilic hydroxyurethanes and polyhydroxyurethanes without the use of isocyanates. They were prepared from biosourced cyclocarbonates, highly reactive towards amines, diamines and polyamines. The providers of cyclocarbonate function are glycerol carbonate and glycerol acrylate carbonate which is a bifunctional reactive. Glycerilic hydroxyurethanes and polyhydroxyurethanes with high oxygenated and nitrogenated potential were then designed via these new glycerilic cyclocarbonates’ intermediates, substitutes of fossil cyclic carbonates such as ethylene or propylene carbonates. The strategy development of high molecular weights glycerilic polyhydroxyurethanes is based on the sequenced reactivity of the glycerol acrylate carbonate: Aza-Michaël reaction on the ethylenic function of the acrylate and aminolysis reaction of the 5-membered cyclic carbonate function. According to the nature of the amine, polyhydroxyurethanes up to 40,000 g/mol were obtained. They can be obtained as foams, gels, resins, depending on the predominance of linear or cross-linked bridges. Intramolecular chemical networks were elaborated by hydrogen bonding between O-H or N-H sites with the oxygen atom of the carbamoyl function of the glycerilic skeleton. That is the reason why carbamoyle functions are less susceptible to hydrolysis and why the chemical and mechanical resistance properties of the glycerilic polyhydroxyurethanes are increased.

This study utilizes recent advances in the analysis of neodymium (Nd) and samarium (Sm) by thermal ionization mass spectrometry (TIMS) to constrain timescales of heating and fluid flow within the lithosphere. Garnet grows during metamorphism and can be linked to its pressure and temperature of growth, while carbonate mineralization ages can be linked to hydrothermal fluid flow. The ability to date these common minerals makes it possible to unravel the timing and duration of tectonometamorphic processes. Garnet from the Eoarchean Nuvvuagittuq Supracrustal Belt (NSB) in Québec, Canada yields an age of 2574.66 ± 0.72 Ma. This is the most precise Neoarchean age reported for this terrane and was achieved through a modified partial dissolution procedure designed to remove the effects of much older (up to 3.8 Ga) inherited mineral growth. An accurate age for the most recent metamorphic garnet in the NSB is critical, as the (controversial) Hadean Nd model age calculations for this terrane depend on the time at which the 147Sm/144Nd systematics were last altered. Carbonate mineralization ages are explored for a diverse group of thirty samples using a novel sequential acid extraction procedure. Through this procedure it is possible to constrain carbonate mineralization in a variety of geologic settings (metamorphic fluid flow, hydrothermal and ore-forming systems) to ± 20 Myr. Zoned and bulk garnet geochronology at ten sites within a unusually localized area (~5 km2) of high temperature granulite-facies metamorphism in Bristol, New Hampshire reveals multiple brief (<1 Myr) periods of garnet growth focused between 393 and 386 Ma, at peak temperatures of 730-850°C. Comparison with garnet growth ages and temperatures , in central Massachusetts (364 Ma at 950°C) and Connecticut (341 Ma at 1000°C) reveal a regional trend of pulsed high temperature garnet growth spanning ~60 Myr from north to south, the same time span bracketed by associated igneous rocks dated via zircon geochronology. Ultrahigh metamorphic temperatures were achieved during the Acadian Orogeny in New England in localized, short pulses, likely related to igneous heating and/or associated fluid flow above and beyond the regional heating due to tectonic overthickening.

No description available.

Since the early 1970's there have been a number of investigations into the preparation of dense sintered hydroxyapatite for medical applications. However, there have been few studies reporting the production of sintered carbonate apatite, which resembles more closely the composition of human bone mineral. This work has studied the precipitation, processing and sintering of carbonate apatites. Crystallisation variables such as temperature and bicarbonate ion concentration have been investigated in order to determine some effects on the size, morphology and composition of carbonate apatite precipitates. By employing the correct conditions, nanoscale precipitates have been produced that have enabled the use of a colloidal filtration route in processing. The effect of sintering atmosphere, green density, and carbonate content were investigated isochronally over a range of temperatures. Isothermal experiments demonstrated the evolution of microstructure and changes in density with time. Results from this study indicated that translucent 99.9% relative density carbonated hydroxyapatite could be produced by sintering in an atmosphere of carbon dioxide and water. Water was found to enhance densification in carbon dioxide furnace atmospheres. The temperature at which maximum densification occurred decreased with carbonate content. Bloating was found to be related to carbonate content as larger expansions were observed in higher carbonate content materials. The partial pressure of water did not effect the composition of the carbonate apatite, whereas the green composition did, contrary to the findings of other workers.

Carbon dioxide capture and storage will be necessary to mitigate the effects of global climate change. Mineral carbonation - converting carbon dioxide gas to carbonate minerals - is a permanent and environmentally benign mechanism for storing carbon dioxide. The peridotite section of the Samail Ophiolite is host to exceptionally well-developed, naturally occurring mineral carbonation and serves as a natural analog for an engineered carbon dioxide storage project. This work characterizes the geochemistry and hydrogeology of peridotite aquifers in the Samail Ophiolite. Water samples were collected from hyperalkaline springs, surface waters, and boreholes in peridotite, and recent mineral precipitates were collected near hyperalkaline springs. Samples were analyzed for chemical composition. Geochemical data were used to delineate water-rock-CO₂ reactions in the subsurface and constrain a reaction path model for the system. This model indicates that mineral carbonation in the natural system is limited by the amount of dissolved carbon dioxide in water that infiltrates deep into the aquifer. The amount of carbon dioxide stored in the system could potentially be enhanced by carbon dioxide injection into the aquifer. Reaction path modeling suggests that injection of water at saturation with carbon dioxide at 100 bars pCO₂ and 90⁰C could increase the carbonation rate by a factor of up to 16,000 and bring carbonation efficiency to almost 100%. Dissolved gas samples from boreholes were collected at in situ conditions and analyzed for chemical composition. Boreholes with pH > 10 contain millimolar levels of dissolved hydrogen and/or methane, indicating these boreholes are located near areas of active low temperature serpentinization. Serpentinization rates were calculated using groundwater flow estimates and dissolved gas concentrations, and range from 3x10⁻⁸ to 2x10⁻⁶ volume fraction peridotite serpentinized per year. Additionally, laboratory incubation experiments show dissolved hydrogen can be stored in sealed copper tubes for at least three months with neither diffusive loss nor production of hydrogen from oxidation of the copper. These experiments demonstrate that copper tubes can be practical containers for collecting and storing dissolved hydrogen in freshwater. Groundwater ages in the peridotite section of the Samail Ophiolite are investigated through analysis of tritium, dissolved noble gases, and stable isotopes. Tritium-³Helium dating was used to estimate the age of modern groundwaters (< 60 years old), and helium accumulation was used as relative age indicator for pre-bomb groundwaters (> 60 years old). Waters with pH < 9.3 have ages from 0-40 years, while waters with pH > 9.3 are all more than 60 years in age. Helium accumulation indicates pH < 10 waters contain only atmospheric and tritiogenic helium, while pH > 10 waters have accumulated 30-65% of their helium from radiogenic production or mantle helium. pH > 10 waters are thus significantly older than pH < 10 waters. Noble gas temperatures are generally around 32⁰C, close to the current mean annual ground temperature. One hyperalkaline borehole has noble gas temperatures 7⁰C cooler than the modern ground temperature, indicating the water at that site may have recharged during a glacial period. Stable isotope data (Δ¹⁸O and Δ²H) for waters with pH < 11 plot between the northern and southern local meteoric water lines, in the typical range for modern groundwater. Hyperalkaline boreholes and springs are enriched in Δ¹⁸O, which suggests they recharged when the southern vapor source dominated, perhaps during glacial periods. Lastly, the potential for in situ mineral carbonation in peridotite is investigated through reactive transport modeling of dissolved CO₂ injection into a peridotite aquifer. Injection was simulated at two depths, 1.25 km and 2.5 km, with reservoir conditions loosely based on the peridotite section of the Samail Ophiolite. The dependence of carbonation extent (mass of carbon dioxide sequestered as carbonate minerals per unit volume) on different factors - such as permeability, reactive surface area, and temperature - was explored. Carbonation extent is strongly controlled by reactive surface area (RSA), with geometric RSA models producing 10 to 770 times more carbonation than conservative RSA models with the same initial permeabilities and temperatures. The ratio of carbon dioxide supply to RSA is also a key factor. The ideal relationship between CO₂ supply and RSA appears to be from 5x10⁻⁴ to 0.2 kg CO₂ /day per m²/m³ RSA. Temperature has also has an impact on carbonation rate: for the same initial permeability, carbonation is 7-35% faster at 90⁰C than at 60⁰C. Simulations of a 50-year carbon dioxide injection show that fracture porosity and permeability do not become overly clogged and carbonation continues at a more or less constant rate. We estimate that one dissolved CO₂ injection well in peridotite could store 1.4 Mtons CO₂ in 30 years with a storage cost of $6/ton. This suggests that an engineered carbon dioxide storage project in peridotite could be both feasible and economical. In situ mineral carbonation in peridotite should continue to be investigated as a safe and permanent mechanism for carbon dioxide storage.

Les besoins actuels en produits de fertilisation et notamment pour le traitement des carences chez le végétal sont en constante augmentation. Cependant, de plus en plus soucieuse de l’environnement, les industries productrices de ces compléments alimentaires souhaitent proposées des solutions de traitements plus durables tant au niveau de leur production que de leur devenir une fois épandue dans la parcelle. Par ailleurs, il a été établi que les cellules végétales peuvent être considérées comme de vraies usines à molécules. Les hydroxyacides en C3 fabriqués par la machinerie cellulaire présentent par exemple de nombreuses propriétés de chélation et de transport. La présence de fonction hydroxyles et carboxyliques leur confèrent en effet la capacité de pouvoir enserrer des métaux et de permettre leur déplacement entre tous les compartiments des cellules, mais aussi entre les différents organes de la plante. Par ailleurs, la présence de ces mêmes molécules au sein des réactions biologiques (respiration, photosynthèse) font d’elles des métabolites assimilables et donc potentiellement dégradables. Les travaux de cette thèse ont donc eu pour objectif de mettre en place une catalyse chimio-enzymatique afin de produire les molécules les plus semblables aux hydroxyacides en C3 végétaux. Dans cette démarche de biomimétisme, nous avons mis au point un protocole de fabrication d’hydroxyacides à partir de glycérol et de carbonate de glycérol dans des conditions similaires au milieu vivant : dans l’eau, à des températures faibles et à pression atmosphérique. Nous avons ainsi réussi à synthétiser des hydroxyacides tel que l’acide glycérique, le 2-oxo1,3-dioxolan-4-carboxylique et l’hémiacétal du carbonate de glycérol. Les travaux de thèse ont également permis de mettre au point une méthode analytique complète pour la visualisation et la quantification de la majorité des hydroxyacides en C3 élaborés selon ce protocole opératoire. Cette méthode regroupe des techniques de caractérisations globales telles que l’Infra-rouge, l’HPLC, l’HPIC, et des analyses plus fines comme la LCMS de haute résolution et la RMN 1D et 2D. Nous avons par ailleurs optimisé la synthèse des hydroxyacides en C3 à partir du glycérol et du carbonate de glycérol grâce à la mise en place d’un plan d’expérience. Les molécules fabriquées présenteraient des propriétés de complexants susceptibles d’être utilisés en agronomie dans le but de remplacer les chélatants actuels issues de réactions plus polluantes de la pétrochimie et générant des substances nocives pour la santé des sols agricoles une fois appliqués.

Micropores can constitute up to 100% of the total porosity within carbonate hosted hydrocarbon reservoirs, usually existing within micritic fabrics. There is, however, only a rudimentary understanding of the contribution that these pores make to reservoir performance and hydrocarbon recovery. To further our understanding, a flexible, object-based algorithm has been developed to produce 3D computational representations of end-point micritic fabrics. By methodically altering model parameters, the state-space of microporous carbonates is explored. Flow properties are quantified using lattice-Boltzmann and network modelling methods. In purely micritic fabrics, it has been observed that average pore radius has a positive correlation with single-phase permeability and results in decreasing residual oil saturations under both water-wet and 50% fractionally oil-wet states. Similarly, permeability increases by an order of magnitude (from 0.6md to 7.5md) within fabrics of varying total matrix porosity (from 18% to 35%) due to increasing pore size, but this has minimal effect on multi-phase flow. Increased pore size due to micrite rounding notably increases permeability in comparison to original rhombic fabrics with the same porosity, but again, multi-phase flow properties are unaffected. The wetting state of these fabrics, however, can strongly influence multi-phase flow; residual oil saturations vary from 30% for a water-wet state and up to 50% for an 80% oil wet fraction. flow when directly connected. Otherwise, micropores control single-phase permeability magnitude. Importantly in these fabrics, recovery is dependent on both wetting scenario and pore-network homogeneity; under water-wet imbibition, increasing proportions of microporosity yield lower residual oil saturations. Finally, in grain-based fabrics where mesopores form an independently connected pore network, micropores do not affect permeability, even when they constitute up to 50% of the total porosity. Through examination of these three styles of microporous carbonates, it is apparent that micropores can have a significant impact on flow and sweep characteristics in such fabrics.

Model peptides were designed, synthesized and conducted a detailed structure-property study to unravel the molecular mechanism of goose eggshell calcification. The peptides were designed based on the primary structural features of the eggshell matrix proteins ansocalcin and OC-17. In vitro CaCO₃ crystal growth experiments in presence of these peptides showed calcite crystal aggregation as observed in the case of the parent protein ansocalcin. The structure of these peptides in solution was established using intrinsic tryptophan fluorescence studies and quasi-elastic light scattering experiments. The structural features are correlated with observed results of the in vitro crystallization studies. / Singapore-MIT Alliance (SMA)