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Evaluation of Durability-Related Field Inspection Data from Concrete Bridges Under Service

Konečný P., Lehner P., Vořechovská D., Šomodíková M., Horňáková M., Rovnaníková P.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

81--89

EN

The level of de gradation of reinforced concrete bridges was evaluated based on the in-situ measurements performed on five reinforced concrete bridges under service located in the Czech Republic. The combined effect of carbonation and chlorides with respect to the corrosion of steel reinforcement, namely the pH and the amount of water-soluble chlorides, were evaluated on drilled core samples of concrete. Based on these parameters, the ratio between the concentrations of Cl- and OH, which indicates the ability of concrete to protect reinforcement, was calculated. All the data were statistically summarized and the relationships among them were provided. The main goal of this study is to evaluate the non-proportional effect of the amount of chlorides per mass of concrete on the risk of corrosion initiation and to localize the “critical” locations in the bridges that are the most affected by the degradation effects.

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Monazite Th-U-total Pb geochronology and P-T thermodynamic modelling in a revision of the HP-HT metamorphic record in granulites from Stary Gierałtów (NE Orlica-Śnieżnik Dome, SW Poland)

Budzyń B., Jastrzębski M., Kozub-Budzyń G. A., Konečný P.

Geological Quarterly

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2015

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Vol. 59, No. 4

700--717

EN

Thermodynamic modelling and monazite Th-U-total Pb dating via electron microprobe were used to improve the pressure, temperature and timing constraints of the HP-HT metamorphic record in granulites from Stary Gierałtów (NE Orlica-Śnieżnik Dome (OSD), SW Poland). The thermodynamic calculations constrained the P-T conditions to 20-22 kbar and ca. 920ºC in the felsic to intermediate granulites and 20-22 kbar and ca. 970ºC in the mafic granulite. These conditions are considered to closely represent the peak temperatures experienced by these rocks. In the intermediate granulite, the matrix monazite and monazite inclusions in garnet and allanite yielded an age of 349±2.5 Ma. An HP-HT metamorphic event with temperature conditions exceeding 900ºC, which are greater than the closure temperatures of most geochronometers, must have disturbed and completely reset the isotopic systems, including the Th-U-Pb system in the monazite. Consequently, this resetting prevented us from constraining the age of potential earlier metamorphic events or the igneous protolith. The 349±2.5 Ma age reflects the timing of the late-stage HP-HT event and cooling below 900ºC related to the initial exhumation of the granulites. A comparison of the new P-T-t constraints with previous data from the NE Orlica-Śnieżnik Dome indicates that the activation of the channels that exhumed the HP rocks to mid-crustal depths most likely initiated at ca. 350 Ma, and all the metamorphic rocks in the OSD likely shared a common Variscan evolution after ca. 340 Ma.

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Stability of monazite and disturbance of the Th-U-Pb system under experimental conditions of 250–350 °C and 200–400 MPa

Budzyń B., Konečný P., Kozub-Budzyń G. A.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 2

405--425

EN

This experimental study provides important data filling the gap in our knowledge on monazite stability under conditions of fluid-mediated low-temperature metamorphic alteration and post-magmatic hydrothermal alterations. The stability of monazite and maintenance of original Th-U-total Pb ages were tested experimentally under P-T conditions of 250–350 °C and 200–400 MPa over 20–40 days. The starting materials included the Burnet monazite + K-feldspar ± albite ± labradorite + muscovite + biotite + SiO2 + CaF2 and 2M Ca(OH)2 or Na2Si2O5 + H2O fluid. In the runs with 2M Ca(OH)2, monazite was unaltered. REE-enriched apatite formed at 350 °C and 400 MPa. The presence of the Na2Si2O5 + H2O fluid promoted the strong alteration of monazite, the formation of secondary REE-enriched apatite to fluorcalciobritholite, and the formation of REE-rich steacyite. Monazite alteration included the newly developed porosity, patchy zoning, and partial replacement by REE-rich steacyite. The unaltered domains of monazite maintained the composition of the Burnet monazite and its age of (or close to) ca. 1072 Ma, while the altered domains showed random dates in the intervals of 375–771 Ma (250 °C, 200 MPa run), 82–253 Ma (350 °C, 200 MPa), and 95–635 Ma (350 °C, 400 MPa). The compositional alteration and disturbance of the Th-U-Pb system resulted from fluid-mediated coupled dissolution-reprecipitation. In nature, such age disturbance in monazite can be attributed to post-magmatic alteration in granitic rocks or to metasomatic alteration during metamorphism. Recognition of potentially altered domains (dark patches in high-contrast BSE-imaging, developed porosity or inclusions of secondary minerals) is crucial to the application of Th-U-Pb geochronology.

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Uranium-rich monazite-(Ce) from the Krivá type granitic boulders in conglomerates of the Pieniny Klippen Belt, Western Carpathians, Slovakia : composition, age determination and possible source areas

Uher P., Plašienka D., Ondrejka M., Hraško L., Konečný P.

Geological Quarterly

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2013

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Vol. 57, No. 2

343–-352

EN

Monazite-(Ce) is a widespread accessory mineral in granitic cobbles of the Krivá type (Zástranie and Krivá localities) in polymict conglomerates of Cretaceous flysch sequences, the Pieniny Klippen Belt, Western Carpathians, NW Slovakia. The granites show leucocratic muscovite-biotite granodiorite composition and peraluminous calc-alkaline, S-type character. The monazite contains unusually high U, commonly 1 to 3, and in some places up to 6.6 wt.% UO2, together with 5 to 7.7 wt.% ThO2. A cheralite-type substitution [Ca(U,Th)REE–2 is the dominant mechanism of U4+ + Th4+ incorporation into the monazite structure in the Zástranie sample, whereas both cheralite- and huttonite-type substitution [(Th,U)SiREE–1P–1] are evident in the Krivá granitic cobble. Uranium alone prefers the CaU4+(REE)–2 mechanism, whereas Th favours the huttonite substitution. The chemical U-Th-Pb dating of monazite from both granitic cobbles show an Early Carboniferous age (346 ± 2 Ma), which is consistent with the main meso-Variscan, orogen-related plutonic activity in the Central Carpathian area (Tatric and Veporic superunits). Analogous U-rich monazites were detected in some Variscan S-type leucogranites of the Rimavica massif (South Veporic Unit) and the Bojná and Bratislava massifs (northern part of the Tatric Unit). On the basis of structural and palaeogeographic data, the North Tatric Zone is the most plausible source of the monazite-bearing granitic boulders in the Pieniny Klippen Belt. However, the source granitic body was most likely hidden by ensuing tectonic shortening along the northern Tatric edge after deposition of the Coniacian–Santonian Upohlav type conglomerates.

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Probabilistic performance assessment of a bridge deck with regards to chloride ion ingress

Konečný P., Tikalsky P. J., Tepke D. G.

Roczniki Inżynierii Budowlanej

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2006

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z. 6

47--50

CS

Příspěvek se zabývá vlivem trhlin na pronikání chloridových iontů do železobetonové mostovky ve které je betonářská výztuž chráněna povlakem na bázi epoxidové pryskyřice. Stochastické chování úlohy je podchyceno s využitím kombinace konečněprvkového modelu a pravděpodobnostní metody Simulation-Based Reliability Assessment (SBRA) [2]. Data užitá pro modelování difuzního koeficientu a krytí výztuže jsou založena na práci studii vykonané na mostech na severovýchodu USA (viz. [1])