Slovak Journal of Civil Engineering Feed

Building A Greener Future: Transforming Industrial Waste Into Sustainable Materials

Fri, 27 Mar 2026 00:00:00 GMT

The construction sector significantly contributes to global carbon emissions, largely due to the widespread use of Ordinary Portland Cement (OPC). This study investigates fly ash, ground granulated blast furnace slag (GGBFS), and calcium carbide residue (CCR) as sustainable precursors for one-part alkali-activated binders. Paste and mortar specimens were prepared using a single activator comprising 4% sodium hydroxide by precursor weight, with CCR incorporated as both an additive and partial replacement at dosages of 0-10%. The results show that a CCR content of 2.5% yields an optimal mechanical performance in GGBFS-based and fly ash–GGBFS blended systems. The effects of ambient and heat curing at 60 °C on geopolymerization and strength development were evaluated. Microstructural analyses using SEM and XRD confirmed the formation of C-S-H and C-A-S-H gels, which supports the strength trends observed. Overall, the study demonstrates that CCR can serve as an effective, low-cost auxiliary activator, which enables the development of sustainable and low-carbon construction materials while offering environmental, social, and economic benefits.

Possible Approaches of Numerical Modelling of Seepage Anomalies and Cut-Off Wall Solutions for Earthfill Dams

Fri, 27 Mar 2026 00:00:00 GMT

Seepage is a frequent cause of dam safety problems and often leads to internal erosion or suffusion. A case study of a small earthfill dam in Slovakia, i.e., the Lozorno Dam, has exhibited anomalies in the development of seepage since its commissioning. This has been manifested by increased water levels in its observation boreholes and the occurrence of fine sand deposits in its relief wells. The objective of this study was to analyze the causes of these anomalies and propose effective remedial measures. The field monitoring data, including the groundwater levels and seepage flows, were evaluated and complemented by numerical modeling. The models were calibrated against long-term measurements in key observation profiles and subsequently applied to assess different remediation scenarios. The results demonstrated that local permeable sandy soils on the left valley slope are the primary source of the anomalous seepage. Parametric studies showed that the construction of a cut-off wall (COW) significantly reduces groundwater levels, seepage, and hydraulic gradients below critical limits. The findings provide practical recommendations for the remediation of earthfill dams in similar geological settings and highlight the importance of integrating monitoring and modeling in dam safety management.

Coupled Effect of Hydrated Lime and Glass Waste Fine Stabilizers on the Mechanical Properties of Lateritic Soil

Fri, 27 Mar 2026 00:00:00 GMT

This study has investigated the coupled effect of hydrated lime (L) and glass-waste fine (GF) stabilizers on the mechanical properties of two different lateritic soil samples (specimens A and B). The stabilizing materials L and GF were mixed together (‘‘LGF’’) at equal percentages of 2%, 4%, and 6% of the mass of the soil samples and thereafter used as the soil stabilizer. Compaction tests, the California Bearing Ratio (CBR) test, and the Unconfined Compressive Strength (UCS) test were conducted to determine the coupled effect of the stabilizing materials. The results obtained show that the maximum dry density (MDD) for the stabilized soils is 1.63kg/m3 at 2% LGF and 1.70 kg/m3 at 4% LGF versus 1.54kg/m3 and 1.61kg/m3 for the untreated soil for both samples, respectively. For the CBR, it increases to 62% at 4% LGF and 72% at 6% LGF, while the UCS value after curing for 24 hours increases by 30.60% and 40.63% for samples A and B, respectively.

Nonlinear Analysis of a Prestressed Beam Subjected to Shear Stress

Fri, 27 Mar 2026 00:00:00 GMT

Nonlinear finite element modelling is a standard tool for the extension of experimental research programs in the field of the design of concrete load-bearing structures. It allows for the expansion of the database of results obtained by a demanding experimental test in order to monitor quantities that could not be recorded during experiments and thus to formulate further conclusions from the research. The paper deals with an analysis of the shear stress of prestressed concrete beams with shear reinforcement. It is focused on investigating the effect of the magnitude of the axial force on the shear resistance. A beam with a height of 0.6 m and an I-shaped cross-section was analysed. A prestressed beam is used as a typical load-bearing element for the construction of road bridges. Two types of models were used: one considered the reinforcement as a discrete element and the second as a model with a smeared reinforcement. The modelling results confirmed only a small effect of the axial force on the increase in shear resistance.

Innovative Slab-Column Connector for a Point-Supported Cross-Laminated Timber Slabs in Tall Buildings – A Numerical Analysis

Fri, 27 Mar 2026 00:00:00 GMT

This study investigates an innovative slab–column connector designed to enhance the structural performance of point-supported cross-laminated timber (CLT) slabs. The proposed connection increases the supported area and pushes the critical circumference further from the column, thereby improving the punching shear capacity. A numerical analysis was conducted to compare the performance of unreinforced and reinforced slabs. The results indicate that the reinforced slab exhibits a punching capacity increase by a factor of 1.63, which shifts the failure mode from rolling shear failure in the unreinforced slab to bending tensile failure in the outer lamellae. The bonded-in steel connector functions as a wider point support and significantly increases the bending stiffness and the critical circumference for the validation of the punching shear. While adhesive failure was mitigated through design modifications, the numerical models were constrained by the assumption of linear elasticity, which limited the representation of the stress redistribution and cracking effects in the CLT.

Flexural Response of RC Slabs with Dosages of Recycled Aggregates and GFRP Reinforcement

Fri, 27 Mar 2026 00:00:00 GMT

The purpose of this study is to assess the mechanical performance of structurally appropriate concrete made from natural aggregates and partially recycled aggregates. Prism, cubic, and cylinder specimens were tested for the static modulus of elasticity, density, and compressive strength as part of the experimental program. Reinforced concrete slabs containing both aggregate types and either steel or GFRP bars were subjected to full-scale bending testing. The results showed that the basic mechanical parameters of concrete were unaffected by the addition of recycled particles. Mixed with recycled materials, the compressive strength, a stiffness, and density of the resulting material were all on a par with those of conventional aggregate concrete. When combined with steel reinforcement, the recycled concrete showed deformation behavior comparable to that of natural aggregate concrete in slab tests, effectively controlled cracks, and demonstrated sufficient load-bearing capacity. In conclusion, the results show that, with proper design, recycled aggregate concrete (RAC) can be a sustainable and structurally sound alternative to conventional concrete mixes. This lends credibility to its use in contemporary building projects and shows that it can help save the environment.

Investigating the Changes in the Groundwater Flow Regime During the Most Recent High Floods in Budapest

Fri, 26 Dec 2025 00:00:00 GMT

Groundwater and surface water have a strong relationship in riverside municipal areas, although obstructed by buildings with underground structures that reach the aquifer. In the study area of Lágymányos (Budapest, Hungary), the groundwater level is highly influenced by the Danube. This research investigates these exchange processes in the case of a flood, and their changes resulting from the construction of two riverside buildings. These buildings were built between the earlier floods in 2010 and 2013 and the recent floods in 2023 and 2024. The specific groundwater discharge was computed by frequently monitoring the groundwater levels. The results are compared to the water level of the Danube and result in loop rating curves. These are approached with ellipses to examine their estimation. If obstructed, the parameters of the ellipses change for the earlier and newer floods. The calculations were also investigated at wells with no underground structures nearby. Further investigations could lead to an easier quantifying of the specific groundwater discharge.

A Modified Oedometer with Control Suction and Temperature

Fri, 26 Dec 2025 00:00:00 GMT

Pressure plate devices have been developed to investigate the hydromechanical behaviour of unsaturated soils using the axis translation technique (ATT). Despite the progress in experimental methods, there are still some problems concerning the ATT application, e.g., the evaporation and condensation of water on cell walls. This investigation discusses a fabricated device-dissolving condensation problem linked to the ATT. A modified suction temperature-controlled oedometer was developed and successfully employed to perform various experiments on unsaturated soils by controlling the vertical net stress, suction, and temperature simultaneously as well as minimizing any problems related to water condensation. The heating system employed for the modified device significantly reduced the water volume errors involving condensation, which varied from 0 to 1.12% in the soil-water characteristic curve (SWCC) test. In addition, the established SWCC of residual granite soil using the modified oedometer was verified by the pressure plate technique.

Projecting the Future Bioclimatic Environment of Bratislava: A UTCI-Based Analysis Under Representative Concentration Pathway Scenarios

Fri, 26 Dec 2025 00:00:00 GMT

This article deals with a future projection of the bioclimatic environment in Bratislava, Slovakia, under ongoing climate change. Using Meteonorm-generated climate data of up to 2100, this research paper presents calculations of the Universal Thermal Climate Index (UTCI) for three Representative Concentration Pathway scenarios, i.e., RCP2.6, RCP4.5, and RCP8.5. The analysis of hourly UTCI values quantifies projected shifts in human thermal stress, with the linear regression revealing strong temporal trends (R² > 0.97, p < 0.05). The main conclusions point to a significant transformation of the city’s climate. Under the high-emissions RCP8.5 scenario, the annual duration of strong heat stress (UTCI ≥ +32°C) is projected to surge from a contemporary baseline of 66 hours to 936 by 2100. Concurrently, annual cold stress (UTCI ≤ 0°C) hours are expected to decrease from 851 to 312. The high degree of variability in the RCP8.5 scenario (CV = 61%) indicates increasing uncertainty in extreme conditions. This dual shift confirms the city’s thermal character will be fundamentally altered, thereby leading to prolonged, stressful summers and milder winters. These findings provide a quantitative evidence base for local policymakers to develop urgent public health and urban adaptation strategies and can further support architects and civil engineers in the future design of resilient buildings through simulation-based solutions.

What Do Machine Learning Models Reveal About Housing Unaffordability in Europe? Implications for Housing Policy

Fri, 26 Dec 2025 00:00:00 GMT

The paper aims to investigate the main factors affecting stress from the housing costs of household in Europe by applying machine learning methods to a set of structural, demographic, market and policy indicators. The research design combines variable selection using the VSURF algorithm with modelling via Random Forest and a subsequent interpretation of the results using SHAP analysis, including the identification of non-linear relationships and interactions between the variables. The data are drawn from the publicly available databases Eurostat, Housing Europe, Numbeo, Horwath HTL, and AllTheRooms. The analysis encompasses all 27 EU member states. It identifies threshold values for individual factors at which their effect on the household cost burden becomes disruptive. In addition, it quantifies the interactions among these variables. The findings thereby underscore the necessity of a comprehensively integrated housing policy. The contribution to knowledge lies in the methodological integration of machine learning with a public policy framework, which allows for a more precise identification of the determinants of housing unaffordability and better targeting of policy interventions.

Assessment of Stable Slopes Through BPSO-Driven Ensemble Models

Fri, 26 Dec 2025 00:00:00 GMT

This study explores a hybrid approach that combines BPSO with ensemble machine learning techniques to improve predictive accuracy in assessments of slope stability. The methodology employs BPSO to optimize the selection of features that are critical to the prediction process. In addition, a grid search technique is utilized to fine-tune the hyperparameters of the ensemble models. The research evaluates the performance of three ensemble models: RF, XGBoost, and LightGBM. For the predictive analysis, six features identified as potentially influential were selected, including: slope height (H), pore water ratio (ru), unit weight (Υ), cohesion (c), slope angle (β), and angle of internal friction (Φ). The effectiveness of the models was assessed using various performance metrics, including the AUC, kappa and accuracy of the predictions. The findings indicate that the hybrid approach, particularly the LightGBM model, significantly outperformed the other models, achieving an AUC of 0.871, a kappa of 0.658 and an accuracy rate of 0.832. This underscores the potential of the proposed hybrid method as a valuable tool for accurately predicting slope stability and mitigating risks associated with slope failures in engineering applications.

Numerical Study of the Load Transfer in Piled Raft Foundations

Fri, 26 Dec 2025 00:00:00 GMT

Piled raft foundations are a reliable solution for improving load distribution and minimizing settlement, particularly in soils where shallow foundations are inadequate. This study focuses on the performance of floating piled raft systems in sandy soils, where controlling settlement is critical. A calibrated three-dimensional finite element (FE) model was developed and validated using experimental load–settlement data to investigate the effect of key parameters, including the number of the pile and the stiffness of the piled-raft foundations. The results show that an optimal configuration of 10 piles achieves a balanced load-sharing ratio of approximately 50% between the raft and piles, which effectively minimizes the settlement without any unnecessary structural redundancy. Beyond this point, additional piles reduce settlement by only 3–5%. The stress distribution analysis highlights the importance of raft–soil interactions, while parametric studies demonstrate how pile numbering and piled-raft stiffness affect the performance of the foundations. This research reinforces the value of numerical modeling as a predictive tool and offers practical design recommendations for cost-effective and sustainable foundation systems in sandy ground conditions.

Combined Effect of Natural Pozzolana and Steel Fibre on the Mechanical Properties of Normal Concrete Subjected to a High Temperature

Fri, 26 Sep 2025 00:00:00 GMT

The objective of this work is to study the effects of high temperatures on the compressive strength, flexural tensile strength, and toughness indices of ordinary concrete reinforced with 0.5% steel fibre. Natural pozzolana was used as a partial cement replacement with two levels of 15% and 30% to improve the characteristics of concrete at 28 and 90 days. The samples produced were subjected to heat exposure of 800°C in a furnace. The results indicate a good correlation between the evolution of the concrete’s mechanical characteristics and the duration of the curing. The experimental results indicate that using natural pozzolana with steel fibers significantly improves the mechanical properties of concrete. Also, natural pozzolana has shown a positive role in the concrete matrix before and after heating. In conclusion, this research highlights the significant potential of utilizing natural pozzolana for the production of sustainable and environmentally friendly concrete.

Digital Twin of Bridge Calibrated by the PSO Method

Fri, 26 Sep 2025 00:00:00 GMT

This paper investigates the use of the Particle Swarm Optimization (PSO) method to calibrate a finite element model (FEM) using experimental tests. The PSO method, a numerical technique that uses a particle swarm, is used to find the optimal solution by evaluating the position of each particle based on its objective function. The objective function in this study focuses on comparing the calculated and measured natural frequencies. The study uses a sophisticated FEM of a cable-stayed bridge with a main span of about 300 m in Bratislava; the bridge was reconstructed in 2017and included a change in the weight of some parts and replacement of the road surface. The weight of any water pipes and the surface treatment of the pavements are taken into account as additional MATLAB parameters in the calibration process. Through an optimization process using the PSO method, these parameters are fine-tuned to achieve a closer match between the natural frequencies obtained from the measurements and the calculations from the FE model. The results of this study demonstrate the effectiveness of the PSO method in improving the fit by tuning these parameters.

Static Analysis of Selected Types of Roof Trusses Considering the Weakening of the Structural Elements

Fri, 26 Sep 2025 00:00:00 GMT

Failures of structural elements in historical roof trusses pose a significant challenge in the preservation and restoration of a cultural heritage. These trusses, traditionally constructed from wood, are exposed to various factors that contribute to their degradation and damage. The most common factors include moisture, insect activity, fungal decay, and mechanical damage caused by geometric deformations or unprofessional alterations. These defects can compromise the structural integrity of an entire roof truss construction and jeopardize the stability of the building. The restoration and conservation of historical roof trusses require a specialized approach involving detailed diagnostics, modern technologies, and the preservation of original construction elements. This paper focuses on identifying the most common structural defects in historical roof trusses, analysing their causes, and presenting possible repair methods aligned with the protection and care principles of a heritage.

Assessment of the Efficiency of the Grout Curtain and Control of the Seepage at Nosice Dam Using Numerical Modeling

Fri, 26 Sep 2025 00:00:00 GMT

The study investigates the interaction between the grout curtain and bedrock foundation of the Nosice Dam, which is located in a geologically heterogeneous environment on the Váh river in Slovakia. By applying numerical modeling (the Finite Element Method) and analyzing water pressure test data, the research aims to assess the effectiveness of a grout curtain in controlling seepage. An extensive parametric study examines the impact of different rock permeability values on the reduction of seepage, which aids in the optimization of the depth of a grout curtain. This approach underscores the importance of advanced numerical modeling for dam safety and seepage control. The results could contribute to the knowledge of dam seepage control measures and could provide valuable insights about similar hydraulic structures. They could potentially mitigate risks, such as internal erosion and foundation instability associated with uncontrolled seepage.

A Study of No-Fines Alkali-Activated Concrete Using Binary Blends of Industrial Wastes

Fri, 26 Sep 2025 00:00:00 GMT

The present investigation focuses on alkali-activated concrete (AAC) without fines as a sustainable substitute for pervious (permeable) concrete made of ordinary Portland cement (OPC). Fly ash and slag, which are industrial waste materials, were utilised as precursors and activated using sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). To maximise strength and permeability, activator-to-source material ratios (ASR: 0.3, 0.4, 0.5), aggregate content (70–80%), and NaOH concentrations (12M and 14M) were undertaken. Under ambient curing conditions, a maximum compressive strength of 17.4 MPa was attained at 14M NaOH and ASR 0.4. Lower NaOH concentrations (12M), however, preserved permeability but decreased strength (16.1 MPa). The porosity improved with increasing the aggregate content, while the strength dropped. By substituting the OPC while preserving durability and drainage efficiency, the study shows that optimised no-fines AAC can be a practical low-carbon, high-permeability material for stormwater management and environmentally friendly construction. Removing sand and substituting alkali activators for OPC promotes sustainability by producing long-lasting concrete, while reducing urban waterlogging.

Evaluation of Thermal Comfort Using Dynamic Simulation: A Case Study of a Kindergarten Classroom in the Czech Republic

Fri, 26 Sep 2025 00:00:00 GMT

This article assesses the indoor environment and thermal comfort in a kindergarten. It is a case study involving experimental measurements and a simulation analysis. During the winter period, experimental measurements were conducted in one of the kindergarten classrooms, collecting data such as indoor air temperature, relative humidity, and carbon dioxide concentration. Based on these data and operational records of the classroom during the measurement period, a model was developed in the DesignBuilder software. This model was utilized to perform an energy simulation followed by a Computational Fluid Dynamics (CFD) simulation. The model was calibrated to closely match the measured data. The output is a qualitative spatial distribution of thermal comfort parameters. The simulations and experiments conducted reveal an unfavourable indoor environment in terms of the thermal comfort and may serve as a basis for designing a more suitable method of room ventilation.

Properties of Concrete with Dosages of Recycled and Industrial Steel Fibers

Fri, 26 Sep 2025 00:00:00 GMT

Currently, there is a significant increase in the number of waste tires in the world. An increase of 1 billion waste tires occurs yearly and consequently results in environmental and health issues. The recovery of material from waste tires includes recycled steel fibers (RSF). RSFs incorporated in concrete significantly improve the tensile strength and energy absorption (RSFRC) of reinforced concrete. The goal of the experimental research presented in this paper is to investigate the workability of fresh concrete with steel fibers as well as the mechanical properties (compressive strength, flexural strength, and fracture energy) of concrete hardened with steel fibers. Experimental research has shown that with a dose of steel fibers, only a slight increase in compressive strength can be observed. Nevertheless, a significant increase in slump value, tensile strength, and fracture energy was observed. The most significant improvement in the relevant concrete parameters was observed with industrial fibers. Still, recycled steel fibers could potentially be a sustainable option for selected fiber-reinforced concrete applications.

Nonlinear Site Response Analysis in District XIII, Budapest

Fri, 26 Sep 2025 00:00:00 GMT

Urban seismic hazard assessments must account for local soil conditions that can significantly alter ground motion characteristics. This study presents a nonlinear one-dimensional (1D) site response analysis for four locations within Budapest’s District XIII—an area characterized by Quaternary Danube sediments underlain by Tertiary clays. The characterization of the seismic subsurface was performed using a multichannel analysis of surface waves (MASW) and seismic cone penetration tests (SCPT) that provided detailed shear wave velocity (Vs) profiles. These profiles were used in nonlinear simulations, including seven spectrum-matched ground motion records. The results demonstrate a pronounced site amplification effect, particularly in the short-period range (0.2–0.4 seconds), which aligns with the natural periods of low-to-midrise buildings typical of the district. Notable inter-site variability was observed, which was influenced by differences in soil stiffness and stratigraphy, with peak amplification factors reaching up to 2.6. The results provide a valuable guideline to formulate the new Hungarian National Annex of Eurocode 8.