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Monitoring and Analysis of Corrosion of Reinforcing Steel in Reinforced Concrete Elements and Structures Using the Acoustic Methods
Timčaková, Kristýna ; Semerák,, Petr (referee) ; Medveď,, Igor (referee) ; Vaněrek, Jan (referee) ; Chobola, Zdeněk (advisor)
The dissertation thesis deals with the study of non-destructive acoustic methods as instruments for monitoring and analysing corrosion of reinforcing steel in reinforced concrete elements. Four acoustic methods were selected for this task - the impact-echo method, the nonlinear acoustic spectroscopy method, the acoustic emission method, and the ultrasonic pulse velocity method. To verify the functionality of these methods, testing was carried out on three sets of reinforced concrete samples that had been exposed to the effects of sodium chloride, which corroded the embedded steel reinforcement in these samples. Suitable parameters were proposed for individual acoustic methods to monitor corrosion of the reinforcements. In addition, experiments were designed to demonstrate the ability of the selected acoustic methods to reveal the corrosion of steel reinforcement and its influence on the concrete matrix and to assess the condition of the degraded elements and structures. The analysis of the measurement results based on their comparison shows the advantages and disadvantages of the individual methods and of their practical applications. To verify the results, correlation with common methods that are currently used for the study of corrosion was carried out and included for example the electrical resistivity measurement of the reinforcement and simultaneous monitoring of the sample surface using a confocal microscope to record the development of microcracks during the degradation.
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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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Komplexní metodika pro nedestruktivní a šetrnou semidestruktivní diagnostiku fyzikálně-mechanických vlastností historických pálených zdících prvků
Cikrle, Petr ; Sokolář, Radomír ; Topolář, Luboš ; Pazdera, Libor ; Anton, Ondřej
Uvedená metodika popisuje základní principy a způsob provádění a vyhodnocování zkoušek zdících prvků určených primárně jako náhrada či doplnění stávajícího historického zdiva. Metodika je určena především pro výběr lícových cihel, které musí mít určité specifické vlastnosti, závislé na prostředí jejich aplikace. Tato metodika je aplikovatelná jak na cihlách starých (použitých, získaných ze zbouraných konstrukcí), tak na nových vyrobených v cihelně, ať už se jedná o běžnou produkci nebo speciálně vyráběné repliky historických cihel. Metodika využívá rozsáhlý soubor zkušebních metod, které však nemusí být vždy v celé šíři využity v závislosti na konkrétních požadavcích na zdící prvky. Novost postupu metodiky spočívá v komplexním zapojení zcela nedestruktivních elektroakustických metod – metody impact-echo, metody rezonanční a metody ultrazvukové impulzové, které posouvají tradiční třídění na výrazně vyšší úroveň. Díky zapojení nedestruktivních zkoušek, jejichž provedení je relativně jednoduché a časově nenáročné, přičemž výsledky jsou u většiny z nich okamžitě viditelné v reálném čase, umožňuje tato metodika provést kvalifikovaný předvýběr souborů cihel vhodných pro náhradu historického zdiva a následně u vybraných souborů provést jejich efektivní třídění a vzorkování, včetně výběru zkušebních vzorků pro ověření fyzikálně-mechanických vlastností cihel tradičními laboratorními metodami. Díky řadě provedených srovnávacích zkoušek (nedestruktivní × destruktivní) na souborech různých cihel z různých období je dokonce možné částečně predikovat trvanlivost (mrazuvzdornost) cihel a provést jejich základní roztřídění do skupin: 1) vhodné pro použití, 2) diskutabilní, 3) zcela nevhodné. Uvedené nedestruktivní zkoušky však mají značný význam i pro posouzení nových cihel, např. pro odhalení textury, která je jednou z hlavních příčin snížené mrazuvzdornosti cihel. Rovněž lze pomocí těchto metod provést třídění cihel přímo ve výrobně (zejména v případě starších typů pecí, kde je poměrně velká variabilita vypálených cihel). V neposlední řadě lze odhalit případnou dodávku špatných (nekvalitních) cihel a zabránit jejich zabudování do stavby. Metodika byla ověřena nejen prostřednictvím velkého množství laboratorních zkoušek cihel různého stáří (cihly gotické, renesanční, barokní, novodobé z 19. století a současné), ale rovněž přímo in situ v rámci rekonstrukce unikátní technické památky – barokního mostu Portz Insel u Mikulova, kde byla přímo aplikována pro výběr náhradních cihel určených pro obnovu chybějících částí mostu (původních barokních, nově vyráběných i použitých ze zbouraných staveb).
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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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Monitoring and Analysis of Corrosion of Reinforcing Steel in Reinforced Concrete Elements and Structures Using the Acoustic Methods
Timčaková, Kristýna ; Semerák,, Petr (referee) ; Medveď,, Igor (referee) ; Vaněrek, Jan (referee) ; Chobola, Zdeněk (advisor)
The dissertation thesis deals with the study of non-destructive acoustic methods as instruments for monitoring and analysing corrosion of reinforcing steel in reinforced concrete elements. Four acoustic methods were selected for this task - the impact-echo method, the nonlinear acoustic spectroscopy method, the acoustic emission method, and the ultrasonic pulse velocity method. To verify the functionality of these methods, testing was carried out on three sets of reinforced concrete samples that had been exposed to the effects of sodium chloride, which corroded the embedded steel reinforcement in these samples. Suitable parameters were proposed for individual acoustic methods to monitor corrosion of the reinforcements. In addition, experiments were designed to demonstrate the ability of the selected acoustic methods to reveal the corrosion of steel reinforcement and its influence on the concrete matrix and to assess the condition of the degraded elements and structures. The analysis of the measurement results based on their comparison shows the advantages and disadvantages of the individual methods and of their practical applications. To verify the results, correlation with common methods that are currently used for the study of corrosion was carried out and included for example the electrical resistivity measurement of the reinforcement and simultaneous monitoring of the sample surface using a confocal microscope to record the development of microcracks during the degradation.
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