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Early stage microstructure development of cement paste modified by crystalline admixture
Hrbek, V. ; Petráňová, Veronika ; Němeček, J.
This paper deals with the effect of crystalline admixture (CA) on the microstructure of the cementitious composite in first four weeks after the production. Previous investigation was performed on reference specimens consisting of pure cement. Samples of pure CA and cement modified by 1% of CA with the same w/c ratio were examined and compared in this paper. By investigation of these materials on the micro-scale, it is possible to identify the development of the microstructure of each and determine the impact of the modification. For this purpose, backscattered electrons microscopy (BSE) with energy-dispersive X-ray spectroscopy (EDX) was used for phase analysis as well as instrumental nano-indentation to obtain micro-mechanical properties. Presented results show the evolution of mechanical properties and microstructure in time and the impact of the crystalline admixture on modified cement.
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Experimental investigation of copper smelter fly ash dissolution in a tropical soil
Petráňová, Veronika ; Ettler, Vojtěch (advisor) ; Kříbek, Bohdan (referee)
In a laboratory pot experiment we investigated a time-dependent release of contaminants from smelter dusts into the soil water and soil. In the experiment we used smelter dusts from two different Cu smelters located in Copperbelt in Zambia (Mufulira and Chambishi). Experimental bags with 0.5 g of dust were placed into pots with 200 g of uncontaminated tropical soil (oxisol) and studied in a time frame of 504 h. Pots were irrigated by deionised water and maintained at the 80 % water holding capacity (WHC). Ten samplings of pore water were performed using the Rhizon pore water samplers. In soil waters, the major released contaminants were Cu, Co and Zn. Concentrations of Cu and Co in soil waters C (from soil with the dust from Chambishi) and M (from soil with the dust from Mufulira) increased during first 48 and 216 h, while concentration of Zn reached highest value in soil waters C and M in 24 and 144 h. This trend has not been observed for Pb, which was released in small amounts and obviously bound to soil constituents. Together with metals, sulfates were highly released into soil waters and affected the speciation of metals (formation of sulfate complexes). Compared to mass loss of the dust from Chambishi with low value (8%), the mass loss of dust from Mufulira after pot experiment were...
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Deformation characteristics of chopped fibre composites subjected to quasi-static tensile loading
Šleichrt, J. ; Adorna, M. ; Neühauserová, M. ; Fenclová, N. ; Petráňová, Veronika
This work presents deformation behaviour of cost effective chopped fiber composites. Use of chopped fibre is advantageous for manufacturing however complex shape parts production technology could be challenging. Batches of samples with different fibres composition were subjected to uni-axial tensile loading to obtain overall materials properties and inspection of proper manufacturing based on local deformation inhomogeneities. Both crossbeam displacement and optical strain measurement were used for elastic characteristics evaluation. Deformation response was derived from full-field optical strain measurements based on digital image correlation method. Relatively large variation of mechanical properties testing of samples was found.
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Comparison of optical methods for characterization of glass mosaic weathering
Kocour, Vladimír ; Petráňová, Veronika ; Valach, Jaroslav
The work presented in this paper is a part of research project supported by Ministry of Culture and devoted to conservation of precious mosaic of 'Last Judgement' on St. Vitus Cathedral in Prague. The aim of the project is to enhance external protective polymeric coating on glass tesserae of mosaic and also to develop optical method for assessment of coating’s surface conditions. The paper concentrates on comparison of various methods for surface evaluation assesses their advantages and disadvantages and also discusses their suitability for long term monitoring of coating state, namely reflectometry, scanning probe microscopy, nanoindentation, white-light interferometry, and scanning electron microscopy. It is found that white-light interferometry and reflectometry methods are the most suitable ones for monitoring purposes.
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