A peer-reviewed serial open access publication, published by the Czech Technical University in Prague, is focused on publishing proceedings from conferences organized or co-organized by the Czech Technical University in Prague. Acta Polytechnica CTU Proceedings is published in electronic version, a printed version is possible only on demand. Each individual issue can also have, besides the ISSN, their own ISBN. Acta Polytechnica CTU Proceedings is indexed by Scopus (since 2020) and DOAJ. Selected Volumes are indexed by Web of Science database. Articles are licenced under a Creative Commons Attribution 4.0 International licence
An evaluation of primary lining deformation using measurements with FBG sensors during a tunnel excavation
The paper presents an evaluation of data gathered with the FBG (Fiber Bragg Gratings) instrument for primary lining deformation measurement, which was installed into primary lining of adit during construction. The evaluation is related to the initial shape of primary lining, and its deflection curve is computed. Definition of appropriate boundary conditions can be verified with the use of geodetic convergence monitoring results. The developed evaluation procedure can be used also for determination of Bragg wavelengths during the design of primary lining monitoring.
Copyright (c) 2026 Jan Záleský, Petr Mayer, Michal Beneš, Jiří Barták, Jan Pruška, Marek Záleský, Zdeněk Sekyra, Monika Lidmilová, Ladislav Šašek https://creativecommons.org/licenses/by/4.0
Special foundation of new buildings in Nové Sady Street in Brno
The construction of the TITANIUM building was started in 2008 near the main railway station in Brno, along the left side of Nové Sady Street. This was followed by the southern extension and expansion of the IN SADY building, then the northward extension of the TITANIUM X and CENTROPOLIS buildings. Various special foundation methods were used in the construction of the building pits and the actual foundation of the buildings. Responses to the realistic form of neogenic clay were also important.
Copyright (c) 2026 Petr Svoboda https://creativecommons.org/licenses/by/4.0
Effect of tangent and secant elastic constants on CCBO stress evaluation in transversely isotropic rock
The Compact Conical Borehole Over-coring (CCBO) method is employed for the determination of the three-dimensional stress state in rock environments. The method utilises a strain gauge cell to quantify the deformation of over-cored rock, the deformation characteristics of which are evaluated in the laboratory. It is assumed that the in situ rock material is homogeneous, elastic and transversely isotropic and it is, therefore, imperative to ascertain the deformation parameters of the transversely isotropic material present in situ. The tangent and secant deformation parameters were taken from previous research and then employed throughout the stress determination process. This paper outlines the fundamental principles of the method and presents results from practical measurements carried out at the Grimsel Underground Research Laboratory in Switzerland. The stress results vary depending on whether alternative deformation characteristics (i.e. tangent or secant) are taken into account during the evaluation process.
Copyright (c) 2026 Alice Petrlíková, Lubomír Staš, Alexej Kolcun, Vlastimil Kajzar, Petr Koníček, Kamil Souček https://creativecommons.org/licenses/by/4.0
Landslide mapping using drone-based method
The article focuses on the possibilities of landslide mapping using photogrammetric and LiDAR measurements from a drone. The measurements are then evaluated and compared with conventional methods.
Copyright (c) 2026 Daniel Turanský, Tomáš Štor https://creativecommons.org/licenses/by/4.0
Modelling diaphragm walls using a time-dependent elasto-plastic material model
This paper utilizes an advanced time-dependent elastoplastic material model for the modelling of diaphragm walls via the Finite Element Method (FEM). After describing the timedependent behaviour of concrete, the Shotcrete material model is specified, and calibration of the material model in long-term conditions based on laboratory testing is carried out. Finally, a real boundary value problem of deep excavation supported by permanent diaphragm walls with the strut is solved. Various strategies of modelling are used and compared. The Shotcrete material model allows simulating creep deformations continuously (that is not stepwise), but when limiting tensile and compressive strength, it is necessary to include reinforcement.
Copyright (c) 2026 Daniela Marková, Juraj Chalmovský https://creativecommons.org/licenses/by/4.0
Derivation of soil shear modulus from push and pull tests of micropiles
The article presents a method for earning soil shear modules from the results of micropile loading tests. The micropile is first loaded with a push force and then with a pull force. The shear modules are derived from two graphs of the dependence of micropile displacements on the loading forces. One represents a push and the other a pull test. Three values of soil shear moduli are obtained, namely for elastic deformation, plastic hardening and the last one after soil failure at a slip plane on micropile shaft.
Copyright (c) 2026 Karel Vojtasík https://creativecommons.org/licenses/by/4.0
A geotechnical investigation for an office building in the foothills of the Bohemian Forest
An office building with a partial basement on an undeveloped plot within Polná na Šumave was proposed. The municipality is located on the border of Boletice Military Training Area which had some specific security measures that had to be respected during the investigation. The detailed geotechnical investigation describes the geological conditions of the area, points out several complications that can be expected and finally proposes solutions to mitigate them.
Copyright (c) 2026 Viktor Sotorník, Petr Černoch https://creativecommons.org/licenses/by/4.0
Calibration of the hardening soil model in excalibre
The hardening soil model is one of the most commonly used constitutive models in engineering practice. This model is based on multi-surface plasticity and combines the well-known Mohr-Coulomb failure criterion, a hardening shear surface and a cap yield surface into a single model. The stress-strain behaviour is improved by including nonlinear elasticity. In this paper a calibration tool for a modified version of the hardening soil model is presented which is currently implemented in the online calibration application called ExCalibre.
Copyright (c) 2026 Do Chinh Phuong, Tomáš Kadlíček, David Mašín, Jan Najser https://creativecommons.org/licenses/by/4.0
Innovative approaches to a solution for surface deformations on earth structures of linear traffic construction
The modification of the slopes of linear transport structures includes humus and grassing which is intended to improve their resistance to erosion. Nevertheless, these slopes are increasingly affected by landslides of the surface layers with the key factors being extreme precipitation fluctuations and the influence of new earthwork technologies. The solution requires an interdisciplinary approach and the introduction of innovative measures. An important role is also played by geodetic monitoring and outputs from modern methods (3D scanning) which provide detailed data on slope changes. A pilot project focused on embankment monitoring in the Hradec Králové region showed the importance of these technologies in dealing with landslides.
Copyright (c) 2026 Václav Mráz, Jiří Vacek, Pavel Dvořák https://creativecommons.org/licenses/by/4.0
51st and 52nd Conference Foundation Engineering Brno 2023 and 2024
51st and 52nd CONFERENCE FOUNDATION ENGINEERING BRNO 2023 and 2024 The traditional yearly conference of Foundation Engineering Brno is organized by the Czech Geotechnical Society. This is the largest annual event in the field, where researches, academicians, designers, investors and contractors present, share and discuss the results of their research and share their experiences with each other. Each year is focused on a certain topical subject. Selected experts from abroad are invited for Keynote lecture for each conference. This issue of Acta Polytechnica Proceedings includes selected scientific papers that were presented at the 51st and 52nd Conference of the Foundation Engineering held in Brno in 2023 and 2024. Key Topics: geotechnical investigation, earth structures, foundation structures, underground structures. Date: November 6 - 7, 2023 and November 11 - 12, 2024 Venue: Brno URL: www.cgts.cz Organized by: Czech Geotechnical Society of the Czech Institution of Civil Engineers Guest editor: Alena Zemanová Scientific comittee: 2023 Jiří Barták Jana Frankovská Taťana Holoušová Eva Hrubešová Jan Pruška Daniel Jirásko Jan Masopust Petr Nosek Michael Remeš Jindřich Řičica Ivan Slávik Peter Turček Ivan Vaníček Petr Svoboda Věra Glisníková Jiří Boštík Lumír Miča Lubomír Klímek 2024 Jana Frankovská Ivan Slávik Věra Glisníková Petr Svoboda Tereza Hamouzová Peter Turček Eva Hrubešová Jaroslav Beňo Lubomír Klímek Lumír Miča Daniel Jirásko Taťana Holoušová Ivan Vaníček Martin Vaníček Jan Pruška Alena Zemanová Michael Remeš Local organizing comittee: 2023 Petr Svoboda Věra Glisníková Jiří Boštík Lumír Miča Lubomír Klímek 2024 Daniel Jirásko Taťana Holoušová Ivan Vaníček Martin Vaníček Jan Pruška Alena Zemanová Michael Remeš Guarantor of the peer review proces: Daniel Jirásko Guarantor of language editing: Renáta Nivenová
Copyright (c) 2026 https://creativecommons.org/licenses/by/4.0
Thermal diffusivity of ATF cladding materials using laser flash technique
Accident tolerant fuel (ATF) cladding materials are designed to improve the fuel behavior in normal operation while further enhancing the material performance in accidental scenarios. The paper presents experimental data on thermal diffusivity for five advanced cladding candidates considered as ATFs, evaluated over a wide temperature range using the laser flash technique. The measured data were evaluated to identify trends in thermophysical behavior in the investigated temperature range. Based on the results, correlations were established to describe the temperature dependence of thermal diffusivity for each material. The analysis also revealed characteristic differences in the thermal diffusivity for various candidates. These findings provide a comparative perspective on the heat transfer capabilities of the tested materials and offer a fundamental experimental basis for their further optimization in accident tolerant fuel applications.
Copyright (c) 2025 Jakub Vrzal, Martin Ševeček, Luka Vlahovic https://creativecommons.org/licenses/by/4.0
Experimental study of the Leidenfrost effect in the context of high heat flux cooling
The behavior of water droplet on heated surfaces is experimentally observed to investigate the properties of the insulating vapor layer, a key element of the boiling crisis phenomenon. The lifetime of droplets on the heated surface is measured and compared with analytical models to examine the formation of the insulating vapor layer thickness between the coolant and the heated wall. The potential for reducing the Leidenfrost effect and increasing the critical heat flux by adjusting the surface roughness is examined to improve the thermohydraulic properties of the first-wall cooling channels. The behavior of water droplets on the heated surface with variable roughness is observed through the acoustic emission method. The behavior of water droplets on heated copper surfaces was experimentally studied using inductive and electrical heating with thermocouple temperature control, camera recording and acoustic emission analysis. The measured droplet lifetimes were compared with analytical models to evaluate the insulating vapor layer thickness. The practical relevance lies in reducing the Leidenfrost effect and increasing the critical heat flux, which can improve the cooling performance of high heat flux components such as tokamak first-wall channels.
Copyright (c) 2025 Vojtěch Smolík, Slavomír Entler, Pavel Zácha, Jan Podaný, Alžbeta Endrychová, Marek Nejman https://creativecommons.org/licenses/by/4.0
Adaptation of SUBCAL subchannel code for square-lattice rod bundles using PSBT benchmark
Subchannel analysis is a commonly used approach for simulating heat transfer and coolant flow in nuclear reactor cores. This paper presents the adaptation of the SUBCAL computational code, originally developed for reactors with a triangular lattice, to configurations with a square lattice. Geometry-dependent computational relations, models and correlations were identified and analyzed based on the research. The selected relations for the square lattice were implemented into the SUBCAL code, and the computational model was optimized for the recalculation of the PSBT benchmark. Verification of the proposed changes was carried out by evaluating the results of the benchmark recalculation against experimental data and through code-to-code comparisons with results from other participating organizations. These modifications and the recalculated PSBT benchmark represent the starting point for validating the SUBCAL code for this type of analysis.
Copyright (c) 2025 Lucie Titzová, Vojtěch Caha, Jiří Čížek https://creativecommons.org/licenses/by/4.0
Dispersion type metal-metal based high-density fuels for nuclear reactors – sample preparation, analysis and examination of LOCA behaviour
Metal-based nulear fuels have been proposed as an alternative to UO2 partly in response to increasing pressure to continually improve nuclear system safety. In this work, a set of High-Density Fuel samples manufactured from depleted uranium alloys and Zr-based matrix have been manufactured and evaluated in the as-manufactured and post-LOCA conditions. A qualitative analysis of the samples showed that the matrix and fuel behaviour is mostly consistent with theory and available research while quantitative analysis revealed a major impact of fuel element geometry on packing density and distribution. Fuel–matrix–cladding interactions of varying intensity have also been observed during fabrication and under LOCA conditions.
Copyright (c) 2025 Petr Šárek, Jakub Krejčí, Tomáš Chmela, Jitka Kabátová https://creativecommons.org/licenses/by/4.0
Numerical simulation of secondary heat exchanger in S-Allegro
This paper presents a computational analysis of the Secondary Heat Exchanger (SHX) in the S-Allegro experimental facility. The S-Allegro facility is a helium circuit which serves as an experimental platform for validating thermohydraulic calculations of helium flow in support of Gascooled Fast Reactor (GFR) development. A computational analysis performed on the SHX included calculations using criterial equations of heat transfer and, most importantly, numerical simulation. Both methods were compared to experimental data and adjusted to achieve a good agreement. The results of the numerical simulations are used to analyse flows in the heat exchanger and identify potential improvements in future design of heat exchangers for GFR. The study provides insights into the thermal performance of helium-water heat exchangers and contributes to the validation of computational methods for GFR technology development.
Copyright (c) 2025 Adam Palouda https://creativecommons.org/licenses/by/4.0
Subtractive gamma discrimination technique for neutron diamond detectors operating in mixed radiation fields
A detection system based on diamond detectors and subtractive discrimination was developed for the measurement of thermal neutrons flux distribution changes during rod drop transient at the VR-1 reactor. The detection system was modified to replace the pulse-shaped method used for discrimination. The electronics available at the department was not able to measure high count rates with the pulse shape discrimination method. Subtractive discrimination allows us to reduce the requirements in the signal processing area, as the shape does not need to be recorded, and therefore the digitizer performance can be significantly lower. For this reason, a pulse stretching amplifier was developed and tested.
Copyright (c) 2025 Ondřej Novák, Ondřej Huml, Martin Kropík, Ľubomir Sklenka https://creativecommons.org/licenses/by/4.0
Microstructural and mechanical property characterization of high-density uranium fuel for light-water reactors
One of the key concepts in the development of accident-tolerant fuels (ATFs) involves the use of high-density fuels, aimed at improving the safety and economics of light-water reactors. This work focuses on the microstructural and mechanical characterization of experimentally fabricated segments of dispersion-type high-density uranium fuels with a zirconium matrix and Zr-based cladding, intended for future testing in research reactors. Both U-Mo alloys and pure uranium metal were investigated, with particular attention given to the influence of thermal treatment on the phase composition and microstructure of the fuel segments. In addition, changes resulting from thermal exposure were evaluated. The research includes the identification of newly formed phases during transient conditions and the analysis of diffusion phenomena in the material. Mechanical properties were evaluated through microhardness measurements, and the results will serve as input parameters for computational simulations using the Serpent code to support the introduction of these fuels in the VR-2 research reactor.
Copyright (c) 2025 Filip Mach, Patricie Halodová, Martin Ševeček, Jakub Krejčí, Petr Šárek https://creativecommons.org/licenses/by/4.0
Project VALVERDE – validation and verification of computational tools to describe corium spill to improve deterministic analyses of severe accidents
The VALVERDE project focuses on the investigation of the melt flow characteristics of the core melt simulant material and the subsequent development of suitable procedures and methodologies for the description of the melt flow of the simulant in a defined geometry. The main aim is to develop an experimental setup in which the melt spreading of the corium will be performed using suitable simulants. The current version of the experimental setup and the CFD simulations of the spreading of the reactor core melt simulant will be presented.
Copyright (c) 2025 Jan Komrska, Pavel Pekárek, Tomáš Hoppe, Pavel Zácha https://creativecommons.org/licenses/by/4.0
Impact of fecral oxide composition on severe accident progression in MELCOR
Experimental studies have shown that the composition of the oxide layer forming on FeCrAl surface depends strongly on the temperature of the environment, with varying fractions of aluminum, chromium, and iron oxides forming under different conditions. In this work, multiple oxide compositions were incorporated into MELCOR simulations for evaluation of their impact on cladding degradation. The weight fractions of aluminum, chromium, and iron oxides were derived from published experimental data, serving as basis for modifications of the material model. Simulations of a representative Loss of Coolant Accident scenario show that these changes significantly affect cladding temperature evolution, oxidation progression, and hydrogen generation. These results highlight the need to account for environmentally dependent behavior when modeling advanced cladding materials in integral codes.
Copyright (c) 2025 Lukáš Hamřík, Peter Mičian, Štěpán Foral, Karel Katovský, Pavel Máca, Jitka Vojáčková https://creativecommons.org/licenses/by/4.0
High-temperature oxidation of non-zirconium materials for ATF
Non-zirconium materials, such as silicon carbide (SiC) and FeCrAl alloys, have attracted interest for developing Accident-Tolerant Fuel (ATF) cladding systems owing to their superior hightemperature oxidation resistance. SiC offers excellent thermal stability, high-temperature properties, irradiation tolerance, and low activation, while FeCrAl alloys provide outstanding oxidation resistance in steam and air through a stable alumina (Al2O3) layer. This study examines their oxidation behavior under simulated severe-accident conditions. Microstructural changes and mechanical integrity after exposure were analyzed using scanning electron microscopy (SEM) and ring compression tests (RCT). The analysis revealed material-specific strengths and limitations, emphasizing the role of temperature and oxidation environment.
Copyright (c) 2025 Alžběta Endrychová, Jakub Krejčí, Martin Ševeček, Martin Cesnek, Claudia Aparicio, David Rada https://creativecommons.org/licenses/by/4.0
Corrosion behaviour of AISI 348 stainless steel in simulated WWER environment and during LOCA conditions
This study investigates the corrosion and high-temperature oxidation behaviour of AISI 348 stainless steel under normal and extreme conditions for potential nuclear applications. Plate specimens were exposed to simulated WWER primary water conditions in an autoclave at 360 °C for extended duration, reaching up to 1659 days. In addition to long-term exposure testing, short-term high-temperature oxidation experiments were performed at temperatures up to 1 400 °C to evaluate oxide scale formation, spallation behaviour, and structural integrity. Characterization techniques included Mössbauer spectroscopy for oxide phase identification, microhardness measurements, and optical microscopy for grain size evaluation. Mechanical testing, including ductility assessment and microhardness measurements, was conducted after high-temperature exposure to evaluate the material’s ability to retain mechanical integrity under accidental conditions.
Copyright (c) 2025 Václav Bouček, Jakub Krejčí, Martin Cesnek, Jitka Kabátová, Martin Ševeček https://creativecommons.org/licenses/by/4.0
Post-CHF nuclear fuel operation with Time-at-Temperature criteria
The dryout and departure from nucleate boiling criteria are used to set safety limits on nuclear heat transfer and temperature values in nuclear reactors. This review argues for the use of a Time-at-Temperature criterion to improve efficiency and utilization of nuclear fuels and reduce costs. To illustrate the importance of such criteria, the review presents the different phenomena of cladding and fuel rods that could impact the continued operation of nuclear reactors, as well as the experiments and operating events that occurred in light-water reactors.
Copyright (c) 2025 Ambre Bertoux, Martin Ševeček https://creativecommons.org/licenses/by/4.0
Šimáně 2025 – International Student Conference on Nuclear Engineering
Nuclear-related sciences and technology have a long and rich history within the Czechoslovakia. Even though the Czech Republic and Slovakia have been separated since 1993, wide cooperation on different levels including education and research still exists. In order to support cooperation and good relations between Czech and Slovak students in nuclear engineering and related disciplines, the Department of Nuclear Reactors organizes annually a student conference on nuclear engineering - Šimáně. Students mainly from Czech and Slovakian nuclear institutes are invited to present their research and share their knowledge. Participants from other foreign institutes are welcomed as well. The conference is named after professor Šimáně, who graduated at the Dr. Edvard Beneš Technical University in Brno. During his early career, he had the opportunity to work with Fréderic Joliot-Curie at College de France. Later, he significantly contributed to the foundation of the nuclear science, industry and education in the Czechoslovakia. He became the first employee of the Institute of Nuclear Physics at the Czechoslovakian Academy of Science, later he became the first director of the Nuclear Research Institute in Řež. Professor Šimáně was well established even on the international level. He was a director at the Joint Institute of Nuclear Research in Dubna or a division director at the International Agency for Atomic Energy. His work was also significantly connected with Faculty of Nuclear Sciences, CTU in Prague where he acted as Dean from 1967 to 1972. The main objective of the conference is to provide an opportunity for BSc., MSc. and Ph.D. students of nuclear-oriented study programmes to publish and present their scientific results achieved during their university studies. Furthermore, it should give the participants experience in the field of presenting their own research, writing scientific papers and also broaden their knowledge throughout the related fields and to remind them rich Czechoslovakian history in nuclear fields by inviting experienced experts. The organizing committee would like to thank all participants for their contributions and also to the CTU in Prague for funding this student conference. The committee also hopes that the work achieved and presented will fulfill the heritage of professor Čestmír Šimáně in current as well as future conferences. Date: June 17 - 18, 2025 Venue: Prague, Czech Republic URL: https://lenochod.fjfi.cvut.cz/simane/ Organized by: Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering Guest editor: Milan Štefánik Martin Cesnek Pavel Suk Martin Ševeček Scientific committee: Milan Štefánik Martin Cesnek Pavel Suk Martin Ševeček Local organizing committee: Martin Ševeček Pavel Suk Štěpán Jedlan Jakub Mátl Ondřej Lachout Josef Sabol Guarantor of the peer review process: Milan Štefánik Guarantor of language editing: Martin Cesnek
Neutron-physical calculations, Material research and application of ionizing radiation, Thermal-physical calculations and accident simulations
Copyright (c) 2025 Editorial Foreword https://creativecommons.org/licenses/by/4.0
Experimental analysis of physical properties of lightweight gypsum plasterboard
This article presents an experimental analysis of a newly developed gypsum plasterboard for dry construction. The new board has a density that is 40 kgm−3 lower than existing boards and was created with an emphasis on conserving resources and reducing the energy consumption required for its production. Because gypsum is the most energy-intensive raw material, the research team focused on minimizing its content. As a result, the new board uses 12 % of mass less gypsum, which translates into an approximately 6 % reduction in CO2 emissions from the annual production process. Crucially, this was achieved while meeting the relevant standard requirements for mechanical, thermal-technical, and fire performance, and maintaining the board’s “sustainable” user properties. The article details the experimental analysis conducted on key mechanical and thermal-technical parameters of the board.
Copyright (c) 2025 Martin Hataj, Jan Jochman, Jan Pošta, Mária Domonkos, Ondřej Zobal, Miroslav Nyč https://creativecommons.org/licenses/by/4.0
A study of the behavior of samples of high-performance concrete shells with filled core exposed to compression
The production of concrete has a huge impact on the environment, especially due to its emission of CO2. Nowadays, it is required to reduce CO2 emissions and at the same time reduce the consumption of non-renewable resources. One way to achieve these goals is through the usage of recycled aggregate. However, when these materials are used, there are significant changes in the properties of concrete, particularly a reduction of mechanical strength, modulus of elasticity, and durability. This article presents the possibility of using a thin shell made of high-performance concrete as core protection of a concrete sample with recycled aggregate to improve the abovementioned properties. Moreover, using high-performance concrete as the outer layer enables the potential of high-performance concrete to be exploited. The article describes the influence of different shell reinforcements on the failure of the samples under compressive stress. A shell layer without additional reinforcement was used for the reference samples. Other sets of samples contained dispersed reinforcement in the form of polypropylene or polyvinyl alcohol fibers. The last reinforcement was a technical textile – a laboratory-prepared composite grid made of carbon rovings. All samples were subjected to a compressive test and the failure mode of the samples was observed in particular.
Copyright (c) 2025 Eliška Kafková, Jan Macháček, Věra Kabíčková, Tomáš Vlach https://creativecommons.org/licenses/by/4.0
Deep learning-based modeling and simulation of heat conduction
The present study focuses on applying deep neural networks (DNNs) to surrogate modeling of heat conduction problems. Deep learning algorithms, valued for their ability to learn hierarchical data representations through multi-layered networks, excel at identifying complex patterns. In this work, the U-Net architecture – widely recognized for its effectiveness in image segmentation – is adapted to model stationary heat transfer, providing a novel approach to a critical challenge in engineering and physics. Specifically, we propose a deep learning-based surrogate model to predict stationary temperature fields in 2D rectangular domains representing two-phase heterogeneous materials.
Copyright (c) 2025 Ondřej Šperl, Jan Sýkora https://creativecommons.org/licenses/by/4.0
Characterization of the microstructure of cement paste exposed to gamma radiation by scanning electron microscopy
Hardened cement paste with a water-cement ratio of 0.4 was examined under five different relative humidity (RH) conditions (11 %, 33 %, 76 %, 96 %, and 100 %). These samples were exposed to gamma radiation with a total dose of 13.82 MGy over 341 days. Scanning electron microscopy (SEM) was the primary tool used for characterizing the samples’ microstructure at a microscale, aided by image analysis (IA), which showed negligible changes in Calcium-Silicate-Hydrate phases but a decrease in Portlandite of 1.5–3.5 % under 33–100 % RH conditions. Point elemental analysis was conducted to determine the (Ca-S)/Si ratio of the inner product, finding a significant increase of up to 20 % at medium RH conditions (33–76 %).
Copyright (c) 2025 Andrea Špaková, Jiří Němeček, Lukáš Procházka, Patricie Halodová, Jiří Němeček https://creativecommons.org/licenses/by/4.0
Mechanical properties of cement composites with plasma-treated waste glass aggregate
This research focuses on evaluating the effect of low-temperature plasma surface treatment of finely ground recycled glass on the mechanical properties of cement composites. The use of waste glass in construction represents an environmentally friendly alternative, but its application may cause alkalisilica reaction (ASR), leading to material degradation. To prevent this phenomenon, plasma treatment was applied with the aim of improving the adhesion of glass particles to the cement matrix, enabling the partial replacement of traditional filler materials. In cement composites, glass primarily functions as an alternative fine aggregate. Its use offers several potential advantages, including improving the pozzolanic properties of the composite, meaning it reacts with calcium hydroxide, thereby contributing to the formation of additional binding phases. In this way, glass not only replaces traditional fillers but also enhances the long-term mechanical properties of the material. However, inappropriate particle size or high reactivity of the glass may lead to ASR, which causes cracking and degradation of the material. Plasma treatment was employed to mitigate these negative effects by enhancing the adhesion between glass particles and the cement matrix, thereby increasing the overall cohesion, strength, and resistance of the composite to environmental influences and degradation. The samples were tested for compressive strength and bulk density after 28, and 168 days of curing. The results indicated that plasma treatment, particularly with oxygen, led to a moderate improvement in mechanical properties compared to untreated samples, but the values did not reach the levels observed in the reference sample without glass powder.
Copyright (c) 2025 Aleš Palička, Zdeněk Prošek, Pavel Tesárek, Oleg Babčenko https://creativecommons.org/licenses/by/4.0
Prestress load distribution modeling for containment digital twin model
This paper examines the prestress load distribution in the ducts of the prestressing tendons of a VVER-type nuclear reactor containment. It introduces a method for distributing the simplified linear load from the prestressing cable onto the surface area of the duct. Furthermore, a procedure for applying this calculation to a detailed numerical 3D model of a containment segment is described. This method can be implemented into computational software, such as OOFEM, to incorporate this more accurately defined load into a comprehensive stress analysis of the segment. Realistic definition of load distribution from prestressing tendons on the surface of the ducts is critical for identifying potential deviations from a uniform prestress distribution within the containment wall. This, in turn, facilitates assessments such as evaluating the extension of the structure’s service life.
Copyright (c) 2025 Matyáš Ratislav, Bořek Patzák, Petr Štemberk, Jan Štěpán https://creativecommons.org/licenses/by/4.0
Prestressed textile reinforced concrete with carbon composite reinforcement
The article deals with the potential of prestressed textile concrete. The prestressing principle, which is nowadays commonly used part of construction, is combined with the developing technology of textile concrete which is concrete reinforced with non-metallic reinforcement. In this case the carbon reinforcement is used because it shows the best mechanical parameters in comparison with glass or basalt reinforcement. The paper presents the advantages of using prestressed textile carbon composite reinforcement of textile reinforced concrete and at the same time deals with problems related to it, such as the correct choice of impregnation using epoxy resin and the technological method of introducing prestress into the sample. The article focuses on comparison between 3 types of epoxy resin, specifically Sikafloor 156, LH 300 and EPOREZIT EPOVILL-A. The results are presented on experimental samples tested in four-point bending test.
Copyright (c) 2025 Jan Macháček, Eliška Kafková, Věra Kabíčková, Tomáš Blažek, Tomáš Vlach https://creativecommons.org/licenses/by/4.0