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Povzetek: Carbon steel, such as concrete-reinforcing steel, tends to undergo corrosion processes when exposed to certain environmental actions. These are the carbonation of concrete and the ingress of chlorides into the concrete from the environment. Many times, the carbonation and chloride contamination are simultaneous processes leading to a harsh corrosion environment and subsequent corrosion problems. Monitoring the state of corrosion is thereby a very useful and powerful tool for following and evaluating the lifetime of reinforced concrete structures. Electrochemical measurements were performed to investigate different forms of carbon steel in simulated concrete pore water at different pH values with and without the presence of chlorides. Morphological characteristics of three different types of carbon steel were studied and SEM/EDX and Raman analyses of the corrosion products were performed. It was found that steel in the form of a sheet has a higher corrosion resistivity than a steel wire and a steel rod, and that the steel rod has a higher corrosion resistivity than the steel wire. The corrosion layer on carbon steel is very diverse; several morphologies were found and analyzed.
Ključne besede: carbon steel, metallography, corrosion, concrete, water
Objavljeno v DiRROS: 26.09.2025; Ogledov: 210; Prenosov: 111
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Povzetek: Alkali-activated materials have emerged as a promising substitute for ordinary Portland cement (OPC) in various applications. This study explores the use of different monitoring techniques for assessing the long-term corrosion behavior of steel in alkali-activated mortars, which remains relatively understudied. Three types of alkali-activated mortars (AAMs) were prepared, based on fly ash, slag, or metakaolin as the precursor material. The corrosion of embedded steel was investigated under wetting and drying cycles with chloride-containing solution for up to one year. Two unconventional techniques were used to monitor corrosion: coupled multi-electrode array sensors (CMEA) to measure partial currents, and electrical resistance (ER) sensors to track thickness reduction. The ER sensors enabled evaluation of general corrosion rates over time, while CMEA provided insight into corrosion initiation and its spatiotemporal distribution. In addition, the corrosion damage on the embedded steel and sensors was evaluated using X-ray computed microtomography (microCT). Distinct corrosion patterns were observed depending on the precursor material: severe corrosion in metakaolin-based AAMs, localized pitting in slag-based AAMs, and moderate damage in fly ash-based AAMs. The study demonstrates the complementary value of CMEA and ER sensors and highlights the challenges of characterizing the long-term corrosion processes in these alternative binder systems.
Ključne besede: corrosion, alkali‐activated materials, coupled multi-electrode array (CMEA), electrical resistance (ER) sensor, X-ray computed microtomography (microCT), visual analysis
Objavljeno v DiRROS: 27.08.2025; Ogledov: 400; Prenosov: 279
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Povzetek: In terms of upcoming energy directive for Nearly Zero Energy Houses (nZEB), we are very much focused on building skin and its properties. Not only thermal characteristics and design, but also durability and environmental aspects should play a role, when deciding on which system will be implemented. External Thermal Insulation Composite Systems or ETICS are generally made of adhesive, insulation, render with mesh reinforcement, primer and finish coat. In the following case study we have presented a life cycle assessment (LCA) study of three ETICS with different types of insulation: expanded polystyrene (EPS), mineral wool and wood fiber board insulation. The study complies to the standard EN 15804:2012. It was conducted in the program Gabi using the Gabi Professional 2012 Database. The scope of the study is covering the production phase (raw material supply, transport to the factory, manufacturing). We have compared the functional unit of 1 sqm of the ETICS system with U-value 0.27 W/m2K taking into account different environmental impact categories. In the calculation the characterization factors proposed by Centre of Environmental Science (CML) at Leiden University were used. The comparison of ETICS shows the important impact of the insulation type used. Also there are some differences in the amount of other ETICS components applied, since changing the type of insulation affects the environmental footprint of the ETICS.
Ključne besede: ETICS, life cycle assessment, nearly zero energy house, insulition types
Objavljeno v DiRROS: 04.03.2025; Ogledov: 694; Prenosov: 327
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Povzetek: This work focuses in monitoring the corrosion processes on copper in a slightly saline environment under oxic conditions, which simulated the first part of high-radioactive waste disposal in bentonite. Besides coupled multi-electrode arrays (CMEA), also electrochemical impedance spectroscopy measurements were implemented. It was expected that this combination of methods would define the general corrosion rate, as well as the spatio-temporal evolution of anodic and cathodic processes. Anodic currents measured by CMEA showed that the corrosion rates decreased with time. Since maximum anodic activity switched between the electrodes, this situation was not individually valid for all the electrodes. At the end of exposure, different spectroscopic techniques were applied in order to identify the modes of corrosion and types of corrosion products. Uneven general corrosion without evident pits was indicated.
Ključne besede: copper, bentonite, saline groundwater, coupled multi electrode array, corrosion
Objavljeno v DiRROS: 14.08.2024; Ogledov: 1216; Prenosov: 667
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Povzetek: A low carbon/ high chromium martensitic stainless steel, X17CrNi16-2, was heat treated using two different hardening and tempering regimes (1050 ◦ C/480 ◦ C or 980 ◦C/600 ◦C) — promoting either a high strength or high toughness state, respectively and further combined with deep cryogenic treatment (DCT) at 196 ◦C for 24 h. Over recent years DCT has been recognized as a promising technique to improve the properties of steel, predominantly with respect to its tensile strength, toughness and wear resistance. The influence of DCT on the hydrogen embrittlement resistance of martensitic stainless steel has not yet, however, been reported. A slow strain rate tensile test (SSRT) with simultaneous cathodic hydrogen charging was selected as the method to assess potential susceptibility to hydrogen embrittlement (HE). Relatively low-intensity hydrogen charging, utilizing a constant current density of 0.1 mA/cm2, in a non-corrosive, slightly alkaline buffer solution, led to a clear reduction in the ultimate tensile stress. This reduction, and therefore the HE susceptibility, was more pronounced in the steel with a higher strength (i.e. that subject to the 1050 ◦C/ 480 ◦C heat treatment condition). Furthermore, DCT did not appear to have any impact on the steel’s mechanical properties in the presence of hydrogen. Fractographic analysis showed clear evidence of HE in the hydrogen-charged specimens. This paper presents results of the SSRT tests and further fractography results, and discusses the impact of conventional and deep cryogenic treatment on HE susceptibility.
Ključne besede: martensitic stainless steel, deep cryogenic treatment, hydrogen embrittlement, slow strain rate tensile test
Objavljeno v DiRROS: 23.05.2024; Ogledov: 1141; Prenosov: 817
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