71. Corrosion behavior of steel in pore solutions extracted from different blended cementsMiha Hren, Tadeja Kosec, Andraž Legat, 2020, original scientific article Abstract: Mortar specimens made from four different types of cement, CEM I, CEM II, CEM III, and CEM IV, were prepared and pore solutions extracted. Three different types of exposure were studied: noncarbonated without chlorides, noncarbonated with chlorides, and carbonated with chlorides. Various electrochemical methods (linear polarization, potentiodynamic polarization measurements) were implemented to characterize the processes of corrosion on steel in these solutions. The type and extent of corrosion products were evaluated by means of various spectroscopic techniques. Specific differences in the type and extent of corrosion damage were determined and compared for each of the extracted pore solutions from the different blended cements. An attempt was made to classify these differences in comparison with the reference cement (CEM I) and in relation to the different types of exposure.
Keywords: corrosion, steel in pore water, blended cements, Raman Spectroscopy
Published in DiRROS: 22.08.2023; Views: 326; Downloads: 150
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72. Validation of combinatorial evaluation of strain-gauge amplifier linearityMiha Hiti, 2020, original scientific article Abstract: This paper describes a validation of a combinatorial calibration technique based calibration procedure for strain-gauge amplifier calibration. The deviation between two strain-gauge amplifiers at calibration using the combinatorial technique is compared to the deviation between the same two amplifiers at calibration on a force calibration machine as a transducer-amplifier chain under unchanged conditions, serving as an amplifier linearity comparator. This enables the validation to be confirmed with a suitable expanded measurement uncertainty of 3 nV/V.
Keywords: strain-gauge amplifier, calibration, combinatorial technique, validation
Published in DiRROS: 21.08.2023; Views: 320; Downloads: 112
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73. Upper Miocene ostracods from the Krško Basin, SE SloveniaMiha Marinšek, Valentina Hajek-Tadesse, Marijan Poljak, Tea Kolar-Jurkovšek, Luka Gale, 2023, original scientific article Abstract: The purpose of this study was to identify the ostracod assemblage from a 43 m thick section of
the Bizeljsko Formation, which constitutes the middle part of the Upper Miocene Posavje Group.
The succession comprises sandstone, siltstone, and marlstone, deposited in a delta front environment. The determined ostracods belong to the families Cyprididae, Cytheridae, Darwinulidae, and Loxoconchidae. In total, 30 species were identified. Additionally, 8 morphotypes were determined at the genus level. The most common genera are Candona, Hemicytheria, and Cyprideis. The assemblage belongs to the Caspiocypris labiata subzone from the upper Pannonian.
The ostracod assemblage from the Krško Basin is similar in species composition to Pannonian ostracod assemblages from Croatia and Serbia.
Keywords: Lake Pannon, Bizeljsko Formation, Pannonian, biostratigraphy, palaeoenvironment
Published in DiRROS: 27.07.2023; Views: 325; Downloads: 154
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74. Environmentally friendly protection of European beech against fire and fungal decay using a combination of thermal modification and mineralisationRožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Nataša Knez, Friderik Knez, Andrijana Sever Škapin, 2024, original scientific article Abstract: The demand for construction timber is continuously increasing, due to its favourable characteristics. However, the adequate protection of wood is key to its successful use, as it is flammable and susceptible to biodegradation. Given that thermal modification enhances the durability of wood, and mineralisation with CaCO3 considerably improves its fire properties, it is worth considering the combined effects of the two methods. European beech (Fagus sylvatica) was selected to determine the effects of a) thermal modification, b) mineralisation through the in-situ formation of CaCO3, and c) a combination of the two procedures, on resistance to decay fungi, reaction to fire and the mechanical properties of the wood. Microscopic analysis and comparisons of the samples before and after exposure to fungi were also conducted. Mineralised wood generally had a slightly alkaline pH value and higher equilibrium moisture content, while thermal modification lowered the equilibrium moisture content. The present study demonstrated the combined effect of thermal modification and mineralisation: the best response to fire as well as resistance to fungi was achieved when the two treatments were combined. Results from the Brinell hardness and three-point bending tests indicate that both modification procedures can slightly impair the mechanical properties of the wood.
Keywords: wood, protection, durability, mechanical properties
Published in DiRROS: 12.07.2023; Views: 376; Downloads: 269
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75. Sensor development for corrosion monitoring of stainless steels in H2SO4 solutionsMiha Hren, Tadeja Kosec, Mari Lindgren, Elina Huttunen-Saarivirta, Andraž Legat, 2021, original scientific article Abstract: Equipment made of different stainless steels is often used in the hydrometallurgical processing industry. In this study, an electrical resistance sensor was developed for monitoring corrosion in acidic solutions at high temperature. Two types of stainless steel were used as the electrode materials, namely grade 316L stainless steel (EN 1.4404) and grade 2507 duplex stainless steel (EN 1.4410). The materials and sensors were exposed to a 10% H2SO4 solution containing 5000 mg/L of NaCl at various temperatures. Results from the sensors were verified using electrochemical techniques and postexposure examination. Results showed that the microstructure played an important role in the interpretation of corrosion rates, highlighting the importance of using an appropriate stainless steel for the production of sensors. Electrochemical tests and postexposure examination both showed that the grade 2507 had a significantly lower corrosion rate compared to the grade 316L. Under industrial‑process conditions, the results for the grade 2507 sensor were promising with respect to sensor durability and performance, despite the extremely harsh operating environment.
Keywords: stainless steel, hydrometallurgical industry, sulphuric acid, electrical resistance sensor, corrosion
Published in DiRROS: 05.07.2023; Views: 375; Downloads: 197
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76. Characterizing steel corrosion in different alkali-activated mortarsNina Gartner, Miha Hren, Tadeja Kosec, Andraž Legat, 2021, original scientific article Abstract: Alkali-activated materials (AAMs) present a promising potential alternative to ordinary Portland cement (OPC). The service life of reinforced concrete structures depends greatly on the corrosion resistance of the steel used for reinforcement. Due to the wide range and diverse properties of AAMs, the corrosion processes of steel in these materials is still relatively unknown. Three different alkali-activated mortar mixes, based on fly ash, slag, or metakaolin, were prepared for this research. An ordinary carbon-steel reinforcing bar was installed in each of the mortar mixes. In order to study the corrosion properties of steel in the selected mortars, the specimens were exposed to a saline solution in wet/dry cycles for 17 weeks, and periodic electrochemical impedance spectroscopy (EIS) measurements were performed. The propagation of corrosion damage on the embedded steel bars was followed using X-ray computed microtomography (XCT). Periodic EIS measurements of the AAMs showed different impedance response in individual AAMs. Moreover, these impedance responses also changed over the time of exposure. Interpretation of the results was based on visual and numerical analysis of the corrosion damages obtained by XCT, which confirmed corrosion damage of varying type and extent on steel bars embedded in the tested AAMs.
Keywords: corrosion, alkali-activated mortars, steel reinforcement, electrochemical impedance spectroscopy, X-ray computed microtomography, visual analysis
Published in DiRROS: 05.07.2023; Views: 411; Downloads: 184
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78. Understanding stability, oligomerization and deactivation during catalytic lignin hydrodeoxygenation by mechanistic reaction micro-kinetics linked with 3D catalyst particle nanotomographyTina Ročnik, Matej Žula, Janvit Teržan, Blaž Likozar, Uroš Maver, Laura Činč Ćurić, Edita Jasiukaityte, Miha Grilc, 2023, original scientific article Published in DiRROS: 23.06.2023; Views: 347; Downloads: 179
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79. Combining mineralisation and thermal modification to improve the fungal durability of selected wood speciesRožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Andrijana Sever Škapin, 2022, original scientific article Abstract: The development of non-biocidal and environmentally friendly systems to protect wood against biological decay has become a high priority in recent years. In the present study the impact of an innovative modification procedure, combining two environmentally friendly modification methods: thermal modification and mineralisation, using an aqueous solution of calcium acetoacetate as a precursor, on the fungal durability of wood was evaluated. European beechwood (Fagus sylvatica) and Norway sprucewood (Picea abies) were selected as model wood species. Wood samples were treated using either a single or combination of both methods and exposed to four different fungi: Gloeophyllum trabeum, Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus. The effect of the different modifications on moisture content, dynamic vapour sorption, contact angle and pH value was also evaluated. Overall, the highest durability against Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus was achieved through thermal modification in both wood species, while the combination of mineralisation and thermal modification has a synergistic effect against degradation by Gloeophyllum trabeum. In the case of beechwood the mass loss decreased from 41% for native to 6% for combined modified samples. We proved that the effectiveness of different treatment against fungal decay of wood were in strong dependence of their moisture content, dynamic vapour sorption, contact angle and pH values. The role of fungi on the morphology of the wood and on crystal structure of formed carbonate was investigated using SEM-EDS analysis.
Keywords: thermal modification, wood mineralization, fungal durability, environmentally friendly modification methods
Published in DiRROS: 20.06.2023; Views: 373; Downloads: 399
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80. Investigation of the British pendulum calibration uncertainty by Monte Carlo simulationVid Primožič, Miha Hiti, 2022, original scientific article Abstract: The paper presents the evaluation of the calibration uncertainty of the British pendulum slip resistance tester using Monte Carlo simulation method. A mathematical model was produced which describes pendulum behavior based on its calibration parameters. The Monte Carlo simulation, programmed in Python, was used for simulating the effect of each of the calibration parameters adjustment within their tolerance intervals, with uniform and triangular probability distribution. Four different tolerance limits were compared: limits from a current international standard, a proposition with reduced limits from recent literature, and two novel propositions, one with reduced but easily achievable limits, and a second one for best practically achievable limits. The results of the simulation show a fundamental standard uncertainty contribution of about 2.8% for pendulum calibration according to current standard limits. Furthermore, they suggest a possible improvement to 0.5%–0.7% as its best practical direct calibration standard uncertainty for reduced limits.
Keywords: British pendulum, simulacija, Monte Carlo, merilna negotovost, odprti dostop
Published in DiRROS: 20.06.2023; Views: 368; Downloads: 198
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