Sandstones have been widely used as a building material since the medieval time all around the Europe. Porosity is one of the main factors affecting the resistance to weathering processes and consequently to the changes of mechanical and physical properties of these stones. Rock material is generally negatively influenced especially during the winter period when frost action takes place. Effect of salt crystals and ice formation depends on the character of pore space, including the pore size distribution. Mercury porosimetry is well known method which provides information about porosity and pore size distribution of samples, but as any other method, it has its own limitations. X-ray microtomography can be used as a complementary method enabling another "view" into the pore space. Main aim of this paper has been to provide the information about the use of these two mentioned methods and comparison of obtained results, within the study of sandstone weathering. The research was focused on two commonly used Czech Cretaceous sandstones - Hořice and Božanov. The stones were exposed to the accelerated durability test which is based on the meteorological data measured in Prague winters from 1998 to 2008. There were described the changes in the area of pores diameters > 5 μm. Use of mercury porosimetry together with X-ray microtomgraphy enabled more detailed understanding of the processes inside the stone structure., Kateřina Kovářová, Robert Ševčík and Zuzana Weishauptová., and Obsahuje bibliografické odkazy
The paper presents the results of experimental examination of the weathering grade of granite rock mass in the medieval Jeroným Mine (Czech Republic). This mine is declared as a cultural heritage site of the Czech Republic therefore, non-destructive methods for determination of the Schmidt hammer rebound value and the ultrasonic pulse velocity were used to minimize negative impact on the historical workings during in situ exploration. Weathering grade of selected parts of the rockmass in underground spaces was classified visually according to the assumed classification (Hencher and Martin, 1982 in Vahed et al., 2009) and the above mentioned measurements were performed in these parts. Results show that the rebound value and the ultrasonic pulse velocity are decreasing with increasing weathering grade for all investigated parts. Therefore this result is possible to use as a supplementary method for evaluation of weathering grade of rock massif in this mine., Markéta Lednická and Zdeněk Kaláb., and Obsahuje bibliografické odkazy
a1_Phyllosilicates are classified into the following groups: 1 - Neutral 1:1 structures: the kaolinite and serpentine group. 2 - Neutral 2:1 structures: the pyrophyllite and talc group. 3 - High-charge 2:1 structures, non-expansible in polar liquids: illite and the dioctahedral and trioctahedral micas, also brittle micas. 4 - Low- to medium-charge 2:1 structures, expansible phyllosilicates in polar liquids: smectites and vermiculites. 5 - Neutral 2:1:1 structures: chlorites. 6 - Neutral to weak-char ge ribbon structures, so-called pseudophyllosilicates or hormites: palygorskite and sepiolite (fibrous crystalline clay minerals ). 7 - Amorphous clay minerals. Order-disorder states, polymorphism, polytypism, and inters tratifications of phyllosilicates are influenced by several factors: 1) a chemical micromilieu acting during the crystallization in any environment, including the space of clay pseudomorphs after original rock-forming silicates or volcanic glasses; 2) the accepted thermal energy; 3) the permeability. The composition and properties of parent rocks and minerals in the weathering crusts, the elevation, and topography of source areas and climatic conditions control the in tensity of weathering, erosion, and there sulting assemblage of phyllosilicates to be transported after erosion. The enormously high accumulation of phyllosilicates in the sedimentary lithosphere is primarily conditioned by their high up to extremely high chemical stability in water-rich environments (expressed by index of corrosion, IKO). Clastic material eroded fro m weathering crusts and transported in rivers contains overwhelming amounts of phyllosilicates inherited from original rocks. In geological literature, the newly formed phyllosilicates crystallizing in weathering crusts including soils as dominating global source of argillaceous lutite accumulations in the sedimentary lithosphere have been overestimate for a long time., a2_The dissolution of silicates in different dense rocks under conditions of weathering and the crystallization of newly formed phyllosilicates has been strongly and for long periods influenced by chemical microenvironments within each clay pseudomorph. Coarser fragments of eroded argillaceous rocks and crystals of phyllosilicates from different bedrocks and soils are very sensitive to impacts and pressure from fragments of co-transported harder and denser rocks and minerals in turbulent fluvial and similar currents. This is the most important mechanical phenomenon supporting the enormous accumulation of lutite rocks rich in phyllosilicates in the sedimentary lithosphere. The summarized new observations and interpre tations are stressed in eleven key poin ts. Erosion and water transportation of detrital material are explained in the terms of hydration, softening, swelling, physical disintegration, grinding, milling, abrasion, delamination, dispersi on, and sorting. The deposition of phyllosilicates in different fluid dynamics of streams is expressed by Re and Fr numbers and explained as unflocculated and floccu lated suspensions. Phyllosilicates an d accompanying detrital minerals in recent marine muds covering vast areas of seas and oceans as well as in lacustrine muds correspond with those transpor ted in fluvial suspensions., Jiří Konta., and Obsahuje bibliografické odkazy
Předmětem článku jsou nálezy raně středověkých skel z Čech, resp. některé typy korálků vyskytující se v širokém časovém období od 6. do 12. století. Na rozdíl od klasického způsobu bádání bylo v tomto případě využito k doplnění charakteristiky vybraných nálezů a ke stanovení chemismu raně středověkých skel jedné z možných spektrálních metod – nedestruktivní rentgenové mikroanalýzy. Cílem autorů bylo zjistit, do jaké míry je chemické složení korálků shodné či naopak proměnlivé, ať už v závislosti na jejich tvaru nebo době výskytu. V rámci sledovaného souboru se podařilo rozlišit pět rozdílných chemických skupin skel. Nakolik byla řada zkoumaných vzorků dostatečně reprezentativní, aby získané závěry měly obecnou platnost, prokáže až další výzkum. Prokazatelně se v raně středověkém sklářství uplatňovala řada různorodých technologických praxí. and This article is concerned with Early Medieval glass finds from Bohemia, and specifically with several types of bead which appear during the broad period of the 6th to 12th centuries. In this case, instead of the classic research methods, the characteristics of selected finds were compared with the chemistry of Early Medieval glass as determined by one of several spectral methods–on–destructive X–ray microanalysis. The aim was to determine to what extent the chemical composition of the beads corresponded, or differed, depending on their shape or the period in which they originated. Within the study assemblage it was possible to separate out five different glass chemical groups. To what extent the range of samples investigated was representative will only become clear in the light of further research. It has been demonstrated that a varied range of technologies were employed in Early Medieval glassmaking.