Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 142-145).

Thesis (B.A.)--University of Wisconsin--Madison, 1946. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [185-226]).

Decreasing amounts of available ideal materials, as well as environmental and economic considerations, lead the cement industry to investigate new products to be used as supplementary cement materials. Dolomite, ideally CaMg(CO3)2, is a carbonate that is already used by the concrete industry as an aggregate but which can be thermally activated to form a mixture of MgO and CaCO3 that is often referred to as “half-burnt dolomite”. The production of this thermally activated dolomite and its use as an addition to Portland cement were investigated in this study. Half-burnt dolomite was successfully obtained under experimental conditions (i.e. temperature and atmosphere composition) which appear compatible with industrial production. The decomposition product consists of nanometric platelets of MgO within a porous calcite matrix. The reactivity of half-burnt dolomite, in aqueous solutions and cement paste, depends on the size of the MgO crystallites and on their accessibility to water (e.g. the surface area of the half-burnt dolomite), both parameters being influenced by the decomposition conditions and the properties of the dolomite. Sintering during partial decomposition seems to control, at least partially, the reactivity of half-burnt dolomite. The reactivity during early hydration stages (i.e. typically < 72 h), which needs to be high while cement is still plastic, is however incomplete. The addition of half-burnt dolomite to Portland cement is not found to influence significantly the properties of cement pastes and even induces an improvement of the compressive strength at 28 days at ~ 10 mass% replacement of cement by half-burnt dolomite. This study suggests that half-burnt dolomite is an interesting potential addition to Portland cement and so more work is recommended (e.g. tests and pilot scale production) with the objective of industrial application.

The Denault Formation (2.1-1.9 Ga) outcrops in the Labrador Trough, northeastern Quebec and western Labrador. The Denault crops out around the town of Schefferville and at Marion Lake, fifty kilometers east-northeast of Schefferville. In June 2007, four stratigraphic sections were measured and samples were collected from eight locations. Occurrences of the Denault near the town of Schefferville contain textural characteristics consistent with deposition on the middle and outer portions of a storm-influenced shallow ramp. Mid-ramp facies consist of intraclastic grainstones with hummocky cross-stratification (HCS), swaley cross-stratification (SCS), current ripples, and graded event beds. Further outboard, grainstones grade into deeper water laminites that are composed of even, mm-scale couplets of flat-lying organic and micritic laminae. Scours within the laminites suggest occasional storm activity. Laminites gradually grade into outer ramp deep-water shales. Separated from these ramp facies by 50km (present day) is an isolated eastern stromatolitic accumulation. This outcrop can be interpreted as the remnant of a near-continuous margin or may simply represent an isolated accumulation that developed on a pre-existing topographic high. Microscopic (2-10µm) lathes of dolomite are interpreted to be pseudomorphs after gypsum. The presence of such pseudomorphs and solution-collapse breccias provide evidence for evaporative conditions during the deposition and early diagenesis of the Denault. Seepage-reflux of brines generated through evaporation during the deposition of the Denault and the overlying Fleming Formation are interpreted to have caused early, mimetic dolomitization in a shallow burial setting. Subsequent burial diagenesis resulted in recrystallization of some rock to fabric-destructive, anhedral dolomite. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-01-07 15:09:43.994

Thesis (Ph. D.)--Ohio state University, 1924. / Published also as the Onio state university. Engineering experiment station. Bulletin no. 31. August 15, 1925. Engineering series. Reprinted from articles by Andrew I. Andrews, George A. Bole and James R. Withrow, published in the Journal of the American ceramic society, v. 8, nos. 2 and 3, February and March, 1925. Autobiography.

Areas underlain by dolomite pose a risk for sinkhole and doline development and subsequently have serious implications towards the safe planning of towns. Research also indicates that almost all sinkholes and dolines formed on dolomitic areas were man-induced and may be contributed to a lack of informed decision making by town planners. Consequently, town-planning decisions must have a guiding plan to avoid unsuitable development on such areas. Such a guiding plan was identified as a Dolomite Risk Management Plan (DRMP). A DRMP has in recent years become a legal responsibility, to be implemented where development is taking place on areas underlain by dolomite according to SANS 1936 and the Geoscience Amendment Act, (16 of 2010). There however currently exists a need to determine to what extent a DRMP contributes to the town planning decisions making process. The aim of this study is to determine to what extent currently existing Dolomite Risk Management Plans contribute to a town planning decision-making process by means of the analysis of four case studies. Four case studies were assessed against a framework compiled through a literature study of all applicable legislation to determine to which extent each complies with the compulsory legislation in South Africa needed to guide safe and sustainable development. The study indicated that a need existed for a DRMP to guide town-planning decisions because it is people‟s constitutional right to be protected and to live in a safe environment. It was also concluded, through the random sampling and assessment of available results from four case studies against criteria from applicable legislation, that currently only 50% are capable of informing and guiding town planning decisions adequately. / M (Environmental Management), North-West University, Potchefstroom Campus, 2015

Areas underlain by dolomite pose a risk for sinkhole and doline development and subsequently have serious implications towards the safe planning of towns. Research also indicates that almost all sinkholes and dolines formed on dolomitic areas were man-induced and may be contributed to a lack of informed decision making by town planners. Consequently, town-planning decisions must have a guiding plan to avoid unsuitable development on such areas. Such a guiding plan was identified as a Dolomite Risk Management Plan (DRMP). A DRMP has in recent years become a legal responsibility, to be implemented where development is taking place on areas underlain by dolomite according to SANS 1936 and the Geoscience Amendment Act, (16 of 2010). There however currently exists a need to determine to what extent a DRMP contributes to the town planning decisions making process. The aim of this study is to determine to what extent currently existing Dolomite Risk Management Plans contribute to a town planning decision-making process by means of the analysis of four case studies. Four case studies were assessed against a framework compiled through a literature study of all applicable legislation to determine to which extent each complies with the compulsory legislation in South Africa needed to guide safe and sustainable development. The study indicated that a need existed for a DRMP to guide town-planning decisions because it is people‟s constitutional right to be protected and to live in a safe environment. It was also concluded, through the random sampling and assessment of available results from four case studies against criteria from applicable legislation, that currently only 50% are capable of informing and guiding town planning decisions adequately. / M (Environmental Management), North-West University, Potchefstroom Campus, 2015

Dans ce travail est présentée une étude systématique de la réactivité des carbonates de magnésium. La constant d'équilibre d'hydromagnésite a été déterminée en réacteurs fermés en fonction de la température de 22,5-75°C et à des pH compris entre 8,6-10,7. L'effet de Ca aqueux sur la cinétique de croissance de la magnésite à 100°C et pH ~ 7,7 a été déterminé en utilisant la microscopie à force atomique hydrothermale et des réacteurs hydrothermaux à circulation. La vitesse d'avancement des marches obtuses et les vitesses de croissance de la magnésite ne varient pas significativement avec la concentration en Ca2+. La solubilité de dolomite a été déterminée de 50-175°C en utilisant une cellule de concentration à électrode d'hydrogène. La valeur du produit de solubilité de la réaction CaMg(CO3)2 = Ca2+ + Mg2+ + 2CO32- générée dans cette étude est à peu près égale à celle prédite par SUPCRT92 à 200ºC mais elle est environ d'un ordre de grandeur plus élevée à 50°C. / This thesis presents a systematic study on the reactivity of Mg-carbonates. The equilibrium constant of hydromagnesite was determined in closed-system reactors as a function of temperature (22.5-75°C) and pH (8.6-10.7). The effect of aqueous Ca on the growth kinetics of magnesite at 100°C and pH ~ 7.7 was determined using hydrothermal atomic force microscopy and hydrothermal mixed-flow reactors. Both, the advancement rates of obtuse steps and the growth kinetics of magnesite are not significantly influenced by the concentration of aqueous Ca. Furthermore, the solubility of dolomite was determined from 50-175°C using a hydrogen concentration cell. The value of the solubility product of the reaction CaMg(CO3)2 = Ca2+ + Mg2+ + 2CO32- derived from this study is nearly equal to that predicted by SUPCRT92 at 200ºC but about one order of magnitude higher at 50°C, suggesting that dolomite is somewhat less stable than previously assumed.

Three islands of study with differing types of dolomite were examined for karst features. Barbados showed that island dolomite could contain dissolutional karst features that form either during or after dolomitization. On Curacao, two types of dolomite were identified. The first documented occurrence of direct dolomite precipitation in situ was found using electron microscopy. Remnant voids from Curacao were classified and used to determine uplift and cliff retreat rates. On Isla de Mona, the influence of microbes in the mixing zone was added to the Dorag model of dolomite replacement. In addition, accounting for glacioeustasy, tectonic, and diagenetic fluctuations hypothesized large volume of dolomite. This study significantly contributes to the understanding of young dolomite formation and diagenesis as well as documenting dissolutional voids within island dolomite.

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