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Radioactive accessory minerals in granitoids and its changes during metamorphosis and alteration.
Tuhý, Marek ; Goliáš, Viktor (advisor) ; Matějka, Dobroslav (referee)
This paper is focused on gathering information about alterations of radioactive accessory minerals in granitic rocks. These minerals become unstable during the influence of fluids and increased temperature and pressure conditions. Allanite is usually metamict therefore it is more easily altered than others. Alteration of monazite is described as decomposing original grains which leads to the formation of secondary minerals such as allanite, apatite, minerals of thorium and epidote. Zircon is the most durable mineral mentioned in this paper. Zircon is altered mainly if it is metamict. Majority of authors agree that during alteration uranium is mobilized into fluids and thorium with REE is incorporate into the secondary minerals.
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Decay of granites used for ashlar masonry in arch bridges
Mach, Kryštof ; Přikryl, Richard (advisor) ; Matějka, Dobroslav (referee)
This thesis deals with the decay of the granite used for ashlar masonry in arch bridges. The aging process and the functionality decrease of the granite tend to be faster in building structures than in natural conditions. Therefore, this ongoing change need to be closely researched. At the beginning, the thesis is focused on general degradation effects on building stone, which can cause for example the reduction of material or finally its damage and destruction. Further, the character of the granite is analysed with the respect to its quality and resistance to negative influences. In this chapter, this thesis also deals with the classification of granitic rocks according to the composition and the structure, which determine the specific name of the rock. Finally, the granite stone is also used in the constructions of arched bridges as their supporting elements, namely vaults and pillars. This type of construction has been widely used in the past. One of the subchapters focuses on the case study of the Legií bridge in Prague, which is a stone arch bridge made of granite blocks. In particular, the author describes the analysis of the sample, which was processed in the petrographic laboratories at the Faculty of Science of Charles University.
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Methods of study of porosity of granitic rocks in relation to rock fabric
Votavová, Klára ; Přikryl, Richard (advisor) ; Krutilová, Kateřina (referee)
This bachelor thesis focuses on granitic rocks, which are often used as a building material. Granite are generally rocks with very low porosity, which can be modified (augmented) due to e.g. weathering processes. Increase of porosity is accompanied with deterioration of other physical parameters and decrease of durability. The thesis focuses, after introducing basic petrographical and petrogenetic characteristics of granitic rocks, on the definition of porosity as a physical property, and on various methods used for its determination. Next part of the thesis discusses some case studies which underpin the significance of porosity of granitic rocks by either using combination of several methods, or by using unconventional ones. According to available data, study of porosity and its relationship to rock fabric should be performed by combining several methods of study, encompassing simple petrophysical determination of open and bulk porosities, and microscopic methods allowing for visualisation of pore space - mineral grains relationships. These can be accompanied with less common method of multidirectional ultrasonic sounding allowing for determination of spatial distribution of microcracks present in granitic rocks.
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Methods of study of porosity of granitic rocks in relation to rock fabric
Votavová, Klára ; Přikryl, Richard (advisor) ; Krutilová, Kateřina (referee)
This bachelor thesis focuses on the problem of porosity of granites. The introductory part of the thesis describes granites, their origin, and classification. Specific concern is given to granites as building materials; therefore factors influencing the quality and durability of building stone are mentioned. Porosity of granites can be observed by several different methods. However, none of the methods provides accurate information on present pores from all points of view. From the methods used, mercury porosimentry performed under laboratory conditions seems to be one of the most effective methods. Other effective approaches are microscopic techniques, such as a scanning electron microscopy with energy dispersive spectrometry and/or optical microscopy. Generally, it is suggested to combine several methods to combine information on the volume and distribution of pores with their shape and size.
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Radioactive accessory minerals in granitoids and its changes during metamorphosis and alteration.
Tuhý, Marek ; Goliáš, Viktor (advisor) ; Matějka, Dobroslav (referee)
This paper is focused on gathering information about alterations of radioactive accessory minerals in granitic rocks. These minerals become unstable during the influence of fluids and increased temperature and pressure conditions. Allanite is usually metamict therefore it is more easily altered than others. Alteration of monazite is described as decomposing original grains which leads to the formation of secondary minerals such as allanite, apatite, minerals of thorium and epidote. Zircon is the most durable mineral mentioned in this paper. Zircon is altered mainly if it is metamict. Majority of authors agree that during alteration uranium is mobilized into fluids and thorium with REE is incorporate into the secondary minerals.
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