The use of backfill in underground mining is increasing due to need for systematic backfilling of mine openings and workings to avoid surface damage, increase safety and contribution to sustainable mining. This study is to investigate backfill materials and new methods suited for systematic selection and application of backfill in underground mines. Laboratory tests were carried out on physical, chemical and mechanical properties of different backfill materials and mixtures thereof. Special attention was paid to materials generated as by-products and other cheaply available materials e.g. fly ash and FGD-gypsum from power plants, natural and synthetic anhydrite. The different material mixtures investigated can be used as a technically and economically viable backfill for underground mines. In summary, the systematic selection of backfill materials from by-products, mine waste and tailings from the mineral processing of mining industry and other industries were suited as a backfill material for test field in China coal fires and recommended for underground potash mines in Thailand.

In dieser Arbeit wurde der Einfluss verschiedener Additive (Carbonsäuren, Phosphonsäuren und Retardan P) auf die einzelnen Teilprozesse des Abbindens von Gips an technischen und synthetischen Halbhydraten unter vergleichbaren Bedingungen untersucht. Vorrangig bei der Keimbildung und beim Kristallwachstum wurde ein Einfluss der Additive beobachtet. Das pH-abhängige Wirkungsoptimum kann mit der Speziation der Additive erklärt werden. Ihre Wirkung wird durch Adsorption auf CaSO4-Oberflächen verursacht. Die Untersuchungen ergaben eine bevorzugte Ca-Affinität mit den Flächen (120) und (001) zunehmend von Citronensäure über Weinsäure, HEDP zu HDTMP. Die in verdünnten homogenen Lösungen erhaltenen Ergebnisse sind nicht direkt auf den Abbindeprozess in Pasten übertragbar. In-situ Ramanspektroskopie und Auswaschexperimente weisen in Pasten auf irreversible Adsorption und ein Überwachsen der Additive hin, was zur Abnahme ihrer Wirkung führt. Auf die Festigkeit der abgebundenen Gipskörper zeigen die Additive kaum Einfluss.

<p>Concrete is in everyday life such as parking lots, buildings, bridges, and more. To keep concrete and its constituents together, binders such as cement are used. Cement’s production process is responsible for 8% of global carbon dioxide emissions as of 2018. With global warming being a severe global issue, the challenge of reducing cement carbon dioxide emissions can be greatly beneficial with even slight improvements. Various solutions to this challenge have developed over the years in the form of processing efficiency, material substitution, or material additives. Of the additives for cement and concrete that have been ventured, nanomaterials have had a strong development in recent years. Specifically, cellulose nanomaterials in the form of nanocrystals, nanofibrils, and more have demonstrated great improvement in cement’s performance resulting in a reduction in cement produced and reduction in emissions. This study expands on the knowledge of cellulose nanocrystals as an additive for cement using the formation factor methodology. Formation factor is a resistivity ratio of the specimen and pore solution that can be used in correlation to the diffusion of chloride ions through the use of the Nernst-Einstein equation. This study also investigates the effect that cellulose nanomaterials have on the mechanical properties and thermogravimetric analysis of gypsum, a material commonly used in cement production that delays the hardening of cement. </p>

Anhydrit II (AII) wird industriell hauptsächlich als Bindemittel bei der Fußbodenestrich-Herstellung eingesetzt. Zur Beschleunigung der Abbindereaktion und der daraus resultierenden schnelleren Verfestigung des Fußbodens wird Kaliumsulfat als Additiv verwendet. Im Rahmen dieser Arbeit wurden anorganische Salze (Sulfate und Chloride) im Vergleich zu Kaliumsulfat hinsichtlich ihrer beschleunigenden Wirkung auf die Abbindereaktion von AII untersucht, um eine mögliche Alternative und einen Mechanismus für die Wirkungsweise der Additive angeben zu können. Unter den verwendeten Salz-Additiven wurde keine Alternative zu K2SO4 für die industrielle Anwendung gefunden. Als Ursache für die beschleunigende Wirkung von K2SO4 wird die Bildung des Doppelsalzes Syngenit auf der Anhydrit-Oberfläche angenommen. Durch epitaktische Beziehungen von Kristallflächen oder den Zerfall des Syngenits wird die heterogene Gips-Keimbildung begünstigt und die Abbindereaktion beschleunigt.

The thesis deals with the integration of phase change materials (PCMs) into building structures. The basic requirement is improved thermal stability during the summer season without using an air conditioner. This can be achieved by increasing the thermal storage capacity of the building structures. If the thermal capacity cannot be increased on the level of weight, phase change materials can be used. These materials are capable of storing latent heat and thus increasing the thermal storage capacity of the building. In the thesis the phase change materials were investigated in a thermal incubator by thermal analysis and, above all, in full-scale experiments using comparative measurements. The comparative measurements were carried out in two attic rooms at the Faculty of Civil Engineering, Brno University of Technology, where in one was used as a reference and the other for the experiment. Manufactured heat storage panels were installed in the experimental room. These panels are composed of a base plate; the capillary tubes placed on it are coated with modified plaster. The gypsum plaster is modified with micro-capsules paraffin for improving the thermal storage capacity. This system is connected to a thermal air-water pump, by which the storage panels can be additionally cooled or heated. In the experimental measurements, different operating modes were investigated and their effect on the indoor environment was evaluated. Thermal storage in PCMs dampens the temperature amplitude in the building during the summer season and, at the same time, allows the stored heat to be discharged during the night. Moreover, the time interval of withdrawing electric energy from the supply mains is much shorter than in the case of air conditioning. A conventional air conditioner must operate simultaneously with the thermal load, i.e. at the time of peak consumption of electric energy. Thanks to the set regimes, the installed system is capable of responding to external thermal condit

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This dissertation includes theoretical and applied components that address the effect of coatings on rates of mineral reactions that occur in acid mine drainage (AMD) environments. The two major projects investigated how diffusion-limited transport of reactants through pore spaces in coatings on mineral grains affects the reaction rate of the underlying mineral. The first project considered the growth of gypsum coatings on the surface of dissolving limestone in anoxic limestone drains (ALD), which reduces the neutralization rate of the dissolving limestone and the subsequent effectiveness of this treatment. The second project investigated the conditions where iron oxyhydroxide coatings form on oxidizing pyrite and the potential strategies to prevent "runaway" AMD by reducing the rate of acid production to the point that the acid can be neutralized by the surrounding rocks. In both studies, experiments were conducted to measure reaction rates for the underlying minerals, as coatings grew thicker. These experimental data were fit to a diffusion model to estimate diffusion coefficients of reactants through pore spaces in coatings. These models are extrapolated to longer times to predict the behavior of the coated grains under field conditions. The experimental results indicate that management practices can be improved for ALDs and mine waste piles. For example, supersaturation with respect to gypsum, leading to coating formation, can be avoided by diluting the ALD feed solution or by replacing limestone with dolomite. AMD can be prevented if the rate of alkalinity addition to mine waste piles is faster than acid is produced by pyrite oxidation. The diffusion model developed in this study predicts when iron oxyhydroxide coatings will become thick enough that alkalinity from the surroundings is sufficient to neutralize acid produced by coated pyrite oxidation and additional alkalinity is no longer required. / Ph. D.