- Prague, Hlavni mesto Praha, Czech Republic
- Geologistedit
The International Year of Planet Earth was proclaimed for 2008 by the General Assembly of the United Nations in its Plenary Session on the 22nd of December 2005. In October 2005, UNESCO's General Conference adopted a similar... more
The International Year of Planet Earth was proclaimed for 2008 by the General Assembly of the United Nations in its Plenary Session on the 22nd of December 2005. In October 2005, UNESCO's General Conference adopted a similar Resolution. The aim of the International Year of Planet Earth is to demonstrate new and exciting ways in which Earth sciences can help future generations meet the challenges involved in ensuring a safer and more prosperous world. For further information on the project and activities in the Czech Republic see www.rokplanetyzeme.cz
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Semi-continuous ultrasonic sounding and acoustic emission were used to study the accelerated alkali silica reactivity (ASTM C1260) of experimental mortar bars with different aggregates. To confirm ultrasonic results, expansion test and... more
Semi-continuous ultrasonic sounding and acoustic emission were used to study the accelerated alkali silica reactivity (ASTM C1260) of experimental mortar bars with different aggregates. To confirm ultrasonic results, expansion test and SEM/EDS examination of ASR-related damage were carried out. It was found that high reactivity aggregates pronounced by high mortar bar dilatancy result in significant decrease of P-wave velocity and high ultrasonic signal attenuation. Acoustic emission can be used for ASR study mainly during first days of ASTM C1260 study to monitor origin of ASR. Later stage of study is limited by high signal attenuation caused by material deterioration. Ultrasonic sounding and acoustic emission monitoring can be used as an effective supplementary tools for the monitoring of internal structure of expanding mortar bars during laboratory tests for the evaluation of alkali silica potential of aggregates.
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Establishment of data base for mechanical characteristics of the common rock materials used for aggregate construction
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The influence of petrographic parameters (modal composition, rock microfarbic parameters like grain size and shape) on the technological properties of rocks used for the production of crushed stone makes one of the overlooked aspects in... more
The influence of petrographic parameters (modal composition, rock microfarbic parameters like grain size and shape) on the technological properties of rocks used for the production of crushed stone makes one of the overlooked aspects in current research and practice of aggregates. In our study, we focused on the detailed examination of volcanic rocks that contribute about 34 % to the total production of crushed stone in the Czech Republic. Principal sources of mostly basaltic rocks are bound to the young volcanic areas in north-west and north Bohemia, and north Moravia; some intermediate and acid varieties are exploited as well. The older volcanic rocks (mostly of Palaeozoic age) come from west and south-west Bohemia. Samples (both crushed fractions and larger non-fractured blocks) taken from about 40 active quarries were subjected to the standard petrographic analysis, geomechanical testing, and technological evaluation. Petrographic analysis included quantitative computer-assisted...
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Research Interests: Geology and Weathering
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... after Güven, 1991, mineral fields constructed according to data given by Grim and Kulbicki, 1961; Schultz, 1969; Weaver and Pollard, 1975. ... from trachytic volcanic ash on SardiniaAnnedda, 1956), and Greece (Ca-bentonite from... more
... after Güven, 1991, mineral fields constructed according to data given by Grim and Kulbicki, 1961; Schultz, 1969; Weaver and Pollard, 1975. ... from trachytic volcanic ash on SardiniaAnnedda, 1956), and Greece (Ca-bentonite from dacite and related tuffs on MilosChristidis and ...
Research Interests: Geology and Geochemistry
Bentonites are chief candidates for engineering barriers in nuclear waste repositories. These smectite-rich rocks are generally considered to be of excellent sorption properties due to the large specific surface area. Extremely low... more
Bentonites are chief candidates for engineering barriers in nuclear waste repositories. These smectite-rich rocks are generally considered to be of excellent sorption properties due to the large specific surface area. Extremely low permeability due to swelling after being hydrated is another favourable property. In our experiment, we focused on the effect of long term (1, 2, 3, 6, 9, 12 and 18 months) of hydration by using different types of "synthetic" ground water (enriched in potassium and/or magnesium) and real ground water. The experiments were conducted on two types of bentonites (Fe-montmorillonite rich bentonite from Rokle deposit and FEBEX bentonite from Spain) under normal laboratory and elevated (95°C) temperature. After the experiments, the detailed analyses of mineralogical changes and pore space were conducted. Although no mineralogical changes were recorded, the treated material exhibited substantial changes in pore space, respectively specific surface area....
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The alkali-silica reaction (ASR) is one of the most damaging factors for concrete structures. ASR originates due to the presence of reactive silica (SiO2) that reacts with alkaline ions under wet conditions. The reaction mechanism... more
The alkali-silica reaction (ASR) is one of the most damaging factors for concrete structures. ASR originates due to the presence of reactive silica (SiO2) that reacts with alkaline ions under wet conditions. The reaction mechanism consists of four different steps: initial attack of OH- compounds on SiO2 at aggregate-cement paste boundary; formation of silanol groups at SiO2 surface; formation of siloxane groups and their polymerization; adsorption of alkaline and Ca2+ ions and formation of alkali-silica gels. Alkali-silica gels tend to absorb water molecules and swell causing increasing internal pressures in concrete and microcracking. The most reactive aggregates are mainly composed of amorphous and/or fine-grained SiO2-rich phases. In the Czech Republic, ASR was observed in deteriorating concrete structures containing very fine-grained quartz (quartz in tuffaceous sandstones and greywackes), as well as quartz indicating variable degree of deformation (quartz in quartzite, granodio...
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ABSTRACT Export Date: 5 November 2012, Source: Scopus
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Five types of quartz sandstones showing variable physical properties (compressive strength 34-96 MPa, water uptake 2.7-8.7 wt. %, open porosity 6.1-16.9 vol. %) were subjected to (1) 6, 12, 24, 48, 72, 96, 120 and 144 cycles of... more
Five types of quartz sandstones showing variable physical properties (compressive strength 34-96 MPa, water uptake 2.7-8.7 wt. %, open porosity 6.1-16.9 vol. %) were subjected to (1) 6, 12, 24, 48, 72, 96, 120 and 144 cycles of freezing/thawing, (2) 5, 10, 15, 20 and 25 cycles of salt crystallization, and (3) combination of both. After certain number of cycles, part of specimens was taken away from the climatic chamber and tested for physical properties (bulk density, bulk porosity, compressive strength, water uptake). The pore space evolution was quantified by mercury intrusion porosimetry. The macroscopically visible modification of the specimens (e.g. alteration of surface by granular disintegration or flaking/scaling) was also documented and quantified by image analysis of digital photographs). Each of the tested parameters shows distinct evolution that can be described by different model. Our study thus confirms that evaluation of the dynamics of weathering highly depends on th...
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Laboratory tests of physical and mechanical properties were performed on amphibolites representing two units from the Kola Superdeep Borehole KSDB‐3 (Russia) − the Proterozoic Karelian Complex (depths of 3043 m, 3530 m and 4389 m) and the... more
Laboratory tests of physical and mechanical properties were performed on amphibolites representing two units from the Kola Superdeep Borehole KSDB‐3 (Russia) − the Proterozoic Karelian Complex (depths of 3043 m, 3530 m and 4389 m) and the Archean Kola–Belomorian Complex (depths of 7951 m, 8942 m and 9904 m). Obtained grain density and bulk density values are nearly identical for all tested samples, but porosities increased slowly with depth. Marked differences in strength properties were found between amphibolite samples from the Karelian Complex and amphibolite samples from the Kola–Belomorian Complex. The uniaxial compressive strength of the samples from the lower part of the borehole is significantly smaller than in samples from the upper part; a similar trend was found for triaxial tests. The values of the deformation modulus, Young's modulus and Poisson's ratio obtained from samples of the Karelian Complex are considerably higher than those from the Kola–Belomorian Complex. Observed mechanical properties are explained by the variable grain‐size distribution and by the spatial arrangement of main rock‐forming minerals. These properties are also influenced by recovery of rocks from great depths.
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The experimental study of rock strength revealed a remarkable mechanical variation in closely related rocks. This variation is explained through a quantitative analysis of microstructures. The oriented dry rock specimens were loaded at a... more
The experimental study of rock strength revealed a remarkable mechanical variation in closely related rocks. This variation is explained through a quantitative analysis of microstructures. The oriented dry rock specimens were loaded at a constant stress rate and the uniaxial compressive strength with deformation, was recorded together. Microstructures were analysed in thin sections using petrographic image analysis, making it possible
Research Interests: Civil Engineering, Geology, Materials Science, Microstructure, Rock Mechanics, and 14 moreImage Analysis, Anisotropy, Quantitative analysis, Porosity, Compressive Strength, Grain size, Experimental Study, Grain size distribution, Microstructures, Quantitative Analysis, Properties of materials, Igneous Rocks, Anisotropia, and Shape Preferred Orientation
To understand the role of the earth scientist in the pre-restoration research of stone monuments, it is necessary to summarize the tasks that he/she can fulfil. Pre-restoration research into building materials is generally conducted to... more
To understand the role of the earth scientist in the pre-restoration research of stone monuments, it is necessary to summarize the tasks that he/she can fulfil. Pre-restoration research into building materials is generally conducted to provide information on types of material, their damage and repair. Although the technologist and restorer must manage the practical aspects of repair, the earth scientist can make a significant contribution in terms of material research. First, he or she can answer questions on the nature of the stone(s) used, their provenance (location of the quarry), and their weathering characteristics in terms of the deterioration of physical and mechanical properties and destruction of rock fabric. Second, the earth scientist can research the physical and mechanical properties of new stone proposed for as a replacement for decayed stonework, including recommendations for alternative materials where stone from the original quarry is no longer available.
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This paper represents the first element of the introduction to this volume, and as such investigates its principal underlying rationale; namely the importance of accurate diagnosis of stone decay in the formulation of effective... more
This paper represents the first element of the introduction to this volume, and as such investigates its principal underlying rationale; namely the importance of accurate diagnosis of stone decay in the formulation of effective conservation strategies. It does this by exploring ways in which perceived similarities between stone decay and human disease have influenced attitudes towards conservation, and how refinements within medical diagnostic strategies can inform future condition assessments of building stones. In doing so, it identifies the importance of looking beyond obvious symptoms to the isolation of the fundamental causes of decay and the factors that control them. These controls are strongly conditioned by accumulated stresses within the stonework. In many buildings these are the product of a complex history involving exposure to a variety of environmental conditions and successive human intervention. Only by understanding these memory effects is it possible to explain cur...
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Experimental laboratory measurements of P-wave velocity confirm the superposition of linearity over non-linearity by a progressive increase in confining pressure. The increase in confining pressure diminishes the influence of microcracks... more
Experimental laboratory measurements of P-wave velocity confirm the superposition of linearity over non-linearity by a progressive increase in confining pressure. The increase in confining pressure diminishes the influence of microcracks that are partly or totally closed. At a certain stress level, the trend of P-wave velocity with applied confining pressure approaches that of a solid without cracks, and a linear increase in elastic wave velocity occurs under high confinement.Several studies have focused on the problem of mathematical approximation of this phenomenon (Carlson & Gangi 1985; Wepfer & Christensen 1991; Greenfield & Graham 1996; Meglis et al. 1996). Although successful within a certain degree of error, they provide neither a multidirectional solution nor the comparison of results with rock fabric. In this study, an analytical relation was applied to describe the P-wave velocity-confining pressure behaviour of quasi-isotropic rocks (granites) and their anisotropic equiva...
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ABSTRACT The Gothic fill masonry of the arches and pillars of the Charles Bridge in Prague (Czech Republic) can be characterised as structural mortared rubble masonry (MRM). The mortar, a mixture of hydraulic lime binder and fine-grained... more
ABSTRACT The Gothic fill masonry of the arches and pillars of the Charles Bridge in Prague (Czech Republic) can be characterised as structural mortared rubble masonry (MRM). The mortar, a mixture of hydraulic lime binder and fine-grained filler (river sand), fastens together larger pieces of natural stone, which are a porous fine-grained clayey–calcareous silicite. A set of specimens were subjected to the uniaxial compressive load. The specimen set was composed of some of the mortars alone, the natural stone alone, or variable mixtures of both (i.e. mortared rubble masonry materials). Along with the ultimate strength, the sample's stress–strain behaviour was recorded. The compressive strength, as well as the modulus of elasticity of the mortared rubble masonry, increased with the proportion of natural stone in the specimens (having a compressive strength of 12.55MPa for a specimen having almost 4vol.% of coarse aggregate, and 61.49MPa for a specimen having almost 82vol.% of coarse aggregate; with a modulus of elasticity of 6GPa for a specimen having almost 4vol.% of coarse aggregate, and over 14GPa for a specimen having 23vol.% of coarse aggregate). The compressive strength of the mortar (6–11MPa) is lower than that of MRM; however, the modulus of elasticity (7–16GPa) can reach the same values as that for MRM. The natural stone, used as the coarse aggregate, showed the highest compressive strength (80–140MPa) and the highest modulus of elasticity (25–28GPa) from among the materials studied. This observation suggests that it is not only the hydraulic lime-based mortar, but also the coarse aggregate (clayey–calcareous silicite), as well as favourable bonding on the natural stone–mortar interface contribute to the superlative mechanical properties of the studied MRM.
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Smectite-rich materials have found many industrial applications over the last century, such as the foundry industry, iron ore pelletisation, well drilling, and absorbents. All these uses are well established for Czech bentonites and... more
Smectite-rich materials have found many industrial applications over the last century, such as the foundry industry, iron ore pelletisation, well drilling, and absorbents. All these uses are well established for Czech bentonites and montmorillonite clays. However, use as engineered barriers in the disposal of high level radioactive waste and spent nuclear fuel opens the possibility of a new market for these industrial minerals. This feature reviews the sources of Czech smectite clays and explains how they can be used in underground nuclear waste repositories.
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Inorganic raw materials, here termed geomaterials, derived from the Earth's crust and used in construction after appropriate processing make a genetically and functionally varied group of mineral resources. Although their basic... more
Inorganic raw materials, here termed geomaterials, derived from the Earth's crust and used in construction after appropriate processing make a genetically and functionally varied group of mineral resources. Although their basic functions have remained almost unchanged for centuries, some new attributes, meanings and impacts on society are still emerging. Geomaterials for construction were among the first mineral raw materials exploited, processed and used by man. They helped in the development of technological and artistic skills of humankind. Accessibility, workability and serviceability are considered here as their main functional attributes, being connected with man's skills to find their occurrence, extract and process them, and then use them in the correct way. However, serviceability is a more complex functional attribute as it also encompasses durability of a material in construction. Durability, that is the ability to withstand the action of weathering/decay processe...
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One of the most important castles of the medieval Teutonic Order—Riga Castle in Latvia—is currently undergoing extensive reconstruction work. This study attempts to summarize recent information about the medieval fresco in the chapel and... more
One of the most important castles of the medieval Teutonic Order—Riga Castle in Latvia—is currently undergoing extensive reconstruction work. This study attempts to summarize recent information about the medieval fresco in the chapel and decorative paintings (17th century CE) on the vaults and vault consoles of the refectory that were found during this work. The restorers acquired a combined knowledge of the materials during the pre-restoration research as well as during the restoration process. This, together with the art historian’s viewpoint, and analytical study conducted by chemical technologist of art restoration and material scientists, allowed for an understanding of the materials present, as well as for a determination of the most probable techniques used for the creation of the frescoes. Based on the results presented in this study, the investigated fresco was mostly created using local materials for the plaster and imported ones for pigments, specifically azurite, malachi...
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Rock sections mainly composed of quartz (coming from orthoquartzite, quartz metagreywacke, pegmatite quartz, vein quartz, chert, and flint) were subjected to experimental etching in 1 M NaOH solution at 80 °C. After 4 h–14 days, the rock... more
Rock sections mainly composed of quartz (coming from orthoquartzite, quartz metagreywacke, pegmatite quartz, vein quartz, chert, and flint) were subjected to experimental etching in 1 M NaOH solution at 80 °C. After 4 h–14 days, the rock sections were analysed using a scanning electron microscopy (SEM) combined with energy-dispersive spectrometer. Representative areas were documented in backscattering mode and analysed using fully automatic petrographic image analysis (PIA). Specific features connected to alkaline etching were observed on the surface of the rock sections: dissolution gaps, accentuation of pre-existing microcracks, etched out parts of aggregates, and the formation of altered silica-rich layer, and alkali–silica gels, all influencing the greyscale spectrum of the BSE microphotographs. Using SEM-PIA, it was possible to quantify the area affected by alkaline etching (etched area) and to express it as a percentage of the total area analysed. A very good correlation was found between the etched area and alkali–silica reaction potential of investigated rocks measured according to an accelerated mortar bar test.
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An enhanced microscopic analysis of pore spaces, as an important part of the entire rock fabric, is proposed. It is based on a special preparatory technique of thin sections. The technique consists of a two-step fixation of porous... more
An enhanced microscopic analysis of pore spaces, as an important part of the entire rock fabric, is proposed. It is based on a special preparatory technique of thin sections. The technique consists of a two-step fixation of porous specimens: the staining of the pore space with a mixture of a low viscosity epoxy resin and a fluorescent dye. The technique is primarily designed to increase the contrast between the pores and rock-forming minerals, and to enhance their microscopic observability. This method can also be used for description of the crack/pore geometry, as well as for the interpretation of other porosimetric parameters.
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pressure shadows, kinking of the phyllosilicates, and mechanical reorientation of the mineral components along s 1 . Preferred orientation of the phyllosilicates and slaty cleavage (s 1) have developed, and represent one of the most... more
pressure shadows, kinking of the phyllosilicates, and mechanical reorientation of the mineral components along s 1 . Preferred orientation of the phyllosilicates and slaty cleavage (s 1) have developed, and represent one of the most pronounced structures along which the rock prefers to split. It was shown that in all cases a good correlation exists between the average point load strength index of the rock samples, the direction of loading, and the petrographic/fabric type in the samples without pre-failed surfaces. Failures in the slate and metasiltstone follow concentrations of preferred oriented phyllosilicates of the s 1 slaty cleavage in the first place. Other parameters (e.g. average grain size, granoblastic texture, quantity of quartz etc.) are of secondary importance and find principal expression in homogeneous rocks and in cases when they were loaded transversely to the main discontinuity. In the pre-failed rocks, the direction of loading played the major role. The relevance...
Volcanic rocks represent about 34 % of the crushed stone marketed in the Czech Republic. These rocks are used for all kinds of construction purposes including roads. In a recent study, we focused on their performance in asphalt concrete... more
Volcanic rocks represent about 34 % of the crushed stone marketed in the Czech Republic. These rocks are used for all kinds of construction purposes including roads. In a recent study, we focused on their performance in asphalt concrete designed for road surfacing. The samples were from 39 active quarries, representing all major volcanic rock types, and belonging to three different geological epochs—Neoproterozoic, Upper Palaeozoic, and Tertiary. The rocks under study encompassed numerous rock fabric subtypes including fine- to coarse-grained, porphyritic, hemicrystalline, etc. These rocks have been studied for their mineralogical composition and rock fabric quantitatively (including image analysis). The polished Stone Value (PSV) of each rock type has been determined following the respective standard. According to Czech standards for road surfacing, PSV above 53 is required, PSV over 56 is required for high traffic and dangerous road sections. From the 39 rock types studied, only 17 (3 basaltic rocks, 5 spilites, 5 melaphyres, 2 rhyolites, 1 porphyry, 1 diabase) fulfil the criteria for general road surfacing. When considering the stricter requirement (PSV above 56), only 5 rock types (3 melaphyres, 1 porphyry, 1 diabase) under study were suitable. Correlations between the selected petrographic features (mineralogical composition, grain size, type of phenocrysts) and the PSV failed. Only for basalts, did an increasing content of olivine phenocrysts lead to a drop of the PSVs, which is in contradiction to the heretofore accepted views on the PSV-petrographic feature relationships.