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Use of acoustic methods for assessing the influence of the composition of cement composites on the course of degradation caused by high temperature
Dvořák, Richard ; Medveď,, Igor (referee) ; Bílek,, Vlastimil (referee) ; Bodnárová, Lenka (referee) ; Chobola, Zdeněk (advisor)
The aim of this work is to optimize the acoustic nondestructive method (NDT) Impact-Echo (IE) as a complementary diagnostic tool for the assessment of concrete structures exposed to high temperatures. Commonly used diagnostic procedures for concrete structures affected by fire are most often limited to in-situ core drilling and subsequent testing of the drilled holes by destructive testing. The Impact-Echo method allows non-destructive testing of variously degraded test specimens and concrete structures, but its use for the assessment of temperature-degraded cementitious composites is hardly ever used in practice. Many studies suggest that Impact-Echo is one of the most suitable non-destructive methods for assessing the rate of degradation by elevated temperature. The dissertation work consists of three main stages, where the first stage is devoted to the production of test specimens of different mixtures and their subsequent degradation by elevated temperature and testing by the IE method and by reference destructive and non-destructive methods. The second stage consists of manufacturing a reinforced concrete element with built-in thermocouples and its subsequent inhomogeneous degradation by a local source of elevated temperature. The controlled degraded element thus prepared contains all grades of thermally degraded concrete tested in the first stage. Subsequent testing consists of verification of standard procedures in the field of acoustic NDT with simultaneous use of experimental modal analysis. In the third stage, the objective is to interpret the measured data from both previous parts, to verify whether within the closed element temperature-degraded areas can be distinguished from one another, or the degree of thermal degradation of concrete. Based on these results, the optimal testing procedure was determined and the basic assumptions for the creation of degrees of damage of the concrete by increased temperature were determined.
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Use of acoustic methods for assessing the influence of the composition of cement composites on the course of degradation caused by high temperature
Dvořák, Richard ; Medveď,, Igor (referee) ; Bílek,, Vlastimil (referee) ; Bodnárová, Lenka (referee) ; Chobola, Zdeněk (advisor)
The aim of this work is to optimize the acoustic nondestructive method (NDT) Impact-Echo (IE) as a complementary diagnostic tool for the assessment of concrete structures exposed to high temperatures. Commonly used diagnostic procedures for concrete structures affected by fire are most often limited to in-situ core drilling and subsequent testing of the drilled holes by destructive testing. The Impact-Echo method allows non-destructive testing of variously degraded test specimens and concrete structures, but its use for the assessment of temperature-degraded cementitious composites is hardly ever used in practice. Many studies suggest that Impact-Echo is one of the most suitable non-destructive methods for assessing the rate of degradation by elevated temperature. The dissertation work consists of three main stages, where the first stage is devoted to the production of test specimens of different mixtures and their subsequent degradation by elevated temperature and testing by the IE method and by reference destructive and non-destructive methods. The second stage consists of manufacturing a reinforced concrete element with built-in thermocouples and its subsequent inhomogeneous degradation by a local source of elevated temperature. The controlled degraded element thus prepared contains all grades of thermally degraded concrete tested in the first stage. Subsequent testing consists of verification of standard procedures in the field of acoustic NDT with simultaneous use of experimental modal analysis. In the third stage, the objective is to interpret the measured data from both previous parts, to verify whether within the closed element temperature-degraded areas can be distinguished from one another, or the degree of thermal degradation of concrete. Based on these results, the optimal testing procedure was determined and the basic assumptions for the creation of degrees of damage of the concrete by increased temperature were determined.
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Study of the effect of the application of cellulose fibers in cementitious composites
Dvořák, Richard ; Herka, Petr (referee) ; Bodnárová, Lenka (advisor)
This diploma thesis is focused on composition and processing of cellulose fibers and their usage in cementitious composites. It describes key attributes of cellulose fibers, which has to be acquired for effective use in cement composites. There are stated effects of cellulose fibers on concrete properties, such as workability, physical and mechanic attributes and freeze-thaw resistance. In experimental part is designed a mixture with portion of cellulose fibers. There has been performed various tests to define the effect of cellulose fibers. There was designed experiment to determine its alkali resistance for fibers itself, and possible changes in microstructure of fibers were analyzed by optic and electron scanning microscope.
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Omezování emisí znečišťujících látek do ovzduší: Rozvoj postupů emisních inventur a emisních projekcí
EGÚ Praha Engineering, a.s., Praha ; KONEKO marketing s.r.o., Praha ; IDEA Envi, s.r.o., Valašské Meziříčí ; SVÚOM s.r.o., Praha ; Kvasar, s.r.o., Zlín ; Český hydrometeorologický ústav, Praha ; Fara, Milan ; Neužil, Vladimír ; Hesoun, Roman ; Jirovský, Ivan ; Kalousková, hana ; Dvořák, Richard ; Vicherek, Vítězslav ; Havlíková, Martina ; Machart, Jiří ; Křikavová, Katarína ; Hnilicová, Helena ; Stehlík, Jaromír ; Machálek, Pavel
Zpráva obsahuje popis prací na etapách 1 a 2 dílčího projektu. Etapa 1: Doplnění aktivitních údajů vybraných skupin zdrojů (dílčí zpráva o provedení analýzy významnosti jednotlivých skupin zdrojů, doplnění aktivitních dat pro významné skupiny zdrojů v letech 1990-2003 - ČSÚ, energetické bilance, resortní statistiky, odborné odhady). Etapa 2: Ověřování údajů provozní evidence zdrojů (realizace úprav SW pro sběr údajů souhrnné provozní evidence za rok 2004, návrh ověřovacích výpočtů pro hodnocení vykazovaných údajů souhrnné provozní evidence).
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