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Driving the circular economy in road construction requires the effective use of secondary materials like recycled concrete aggregate (RCA) and fly ash (FA). A key obstacle is the performance trade-off in concretes incorporating both materials. This research investigates feasible mix designs for road concrete, using RCA as a full gravel replacement and FA as a cement substitute. Polypropylene fiber (36 mm) and a superplasticizer were utilized to mitigate fresh and hardened state drawbacks. The experimental program included 15 modified mixtures with recycled aggregate and 3 control mixtures with natural aggregate. The workability of all concrete mixtures was kept constant at slump class S1. Road concretes with RCA, containing a 10–12% FA by cement replacement, at least 2 kg/m3 of polypropylene fiber (PF), and 4 kg/m3 of superplasticizer (SP), achieve compressive strength of at least 50 MPa and flexural strength of no less than 5 MPa at the design age. This performance is comparable to that of control mixtures. Furthermore, the abrasion resistance ranges between 0.48–0.50 g/cm2, and the brittleness index falls within 0.095–0.100, significantly enhancing the durability of concrete for rigid pavement applications. The conducted cradle-to-gate life-cycle assessment (stages A1–A3) of the constituent materials for 1 m3 of concrete indicates the following environmental impacts: Global Warming Potential (GWP) of 195 kg CO2 equation, Non-renewable Primary Energy Demand (PENRE) of 1140 MJ, Abiotic Depletion Potential for Fossil resources (ADPF) of 1120 MJ, Acidification Potential (AP) of 0.45 mol H+ equation, and Eutrophication Potential (EP) of 0.07 kg PO43− equation It is established that the modified compositions not only meet the required performance criteria but also contribute to the goals of resource conservation in road construction.
This study investigates the properties of concrete incorporating recycled aggregates (RAs) for rigid pavement applications. A 15-point three-level experimental design was used to vary three composition factors: Portland cement substitution with fly ash (FA), and dosages of a superplasticizer (SP) and polypropylene fibers (PFs). A set of experimental-statistical models (ES models) was developed to predict the concrete strength, abrasion and frost resistance (FR), water absorption (WA), and global warming potential (GWP). This study aimed to develop a material that achieves both adequate mechanical performance for pavement applications and enhanced environmental sustainability by incorporating RAs and FA. The results demonstrate that replacing up to 13% of cement with FA does not compromise the splitting tensile strength or FR. For non-fibrous concrete, this substitution increases FR by approximately 50 freeze-thaw cycles. Application of PFs (2.4-3 kg/m3) enhances splitting tensile strength by 14-16% and improves FR by about 50 cycles. Using response surface methodology (RSM), optimal concrete compositions were identified that meet all target criteria: compressive strength >= 40 MPa, flexural strength >= 5 MPa, FR >= F200 (cycles), and abrasion resistance (AR) <= 0.5 g/cm2, while simultaneously minimizing GWP. An additional optimum composition was determined by imposing a constraint on splitting tensile strength of >= 4.5 MPa. This graphical optimization approach, utilizing two-factor interaction diagrams, provides an effective and visual methodology for practical concrete mixture design. The novelty of the method lies in the discretization of the factor space, which enables efficient identification of optimal concrete mixture compositions.
The article examines the process of formation, development and transformation of the resort system of Odesa and the adjacent estuaries in the 19th–20th centuries in a broad historical, cultural, medical and urban planning context. The decisive role of natural factors – the Black Sea and the system of estuaries (Kuyalnytsky, Khadzhibeysky, Sukhoi) – as unique medical and health-improving resources that led to the formation of Odesa as a multifunctional balneological and climatic resort is substantiated. Based on archival materials, scientific works of doctors, spa specialists and naturalists, the evolution of the resort infrastructure from the first estuary mud baths and warm sea bath establishments of the 19th century to an extensive network of sanatoriums, rest homes, research and clinical institutions in the Soviet period is traced. Particular attention is paid to the spatial organization of resorts, the formation of transport links, the development of summer cottages, parks and recreational areas, as well as the impact of city improvement (water supply, sewage, tramway connection, electrification) on the growth of the popularity of local resorts. The social composition of visitors and the change in the resort audience are considered – from representatives of the middle classes to mass health improvement in the 20th century. The impact of military events, industrialization and state policy on the functioning of resorts, their specialization and restoration in the post-war years is analyzed. It is proven that the combination of natural healing potential, scientific basis, medical innovations and urban development provided Odesa with the status of a medical place of national importance and contributed to the formation of a holistic resort region of the Northern Black Sea Region. The historical experience of the development of Odesa resorts is considered as an important resource for the modern understanding and preservation of resort heritage and sustainable use of natural healing factors.
In the context of contemporary urbanization processes, climate change, and the growing demand for high-quality and affordable housing, European cities are facing the need to transition toward sustainable and integrated models of spatial development. One of the key forms of such transformation is multifunctional residential complexes that combine housing, public spaces, service facilities, and elements of green infrastructure. The aim of this study is to conduct a comprehensive analysis of the architectural and urban planning foundations underlying the formation of contemporary residential complexes and multifunctional residential ensembles in the city of Karlsruhe as key elements of a sustainable urban environment, as well as to determine their role in the transformation of the spatial structure, functional organization, and quality of the residential environment within the framework of compact and integrated urban development. The study applies a comprehensive architectural and urban-planning approach, including an analysis of the urban structure of Karlsruhe, a typological study of residential and multifunctional complexes, and an examination of key projects—BadenCarré, Rintheimer Feld, and Ettlinger Tor. Particular attention is paid to issues of multifunctionality, the organization of public spaces, the integration of social infrastructure, and the application of sustainable development principles. As a result of the study, it has been established that contemporary residential complexes in Karlsruhe form a qualitatively new type of organization of urban residential development based on high density, multifunctionality, and orientation toward public transport. Such complexes contribute to reducing transport dependency, improving the quality of the residential environment, and enhancing the resilience of the urban structure. The findings confirm that the experience of Karlsruhe can be regarded as a promising model for the transformation of residential development in European and post-socialist cities.
The intensification of territorial and economic integration increases the role of cross-border cooperation in regional development. However, border regions lack a standardised methodology for assessing its effectiveness, while existing approaches mainly focus on funding and the number of projects without adequately reflecting their socio-economic impact. The study aims to improve the methodological framework for assessing cross-border cooperation by developing a system of criteria and indicators and a methodology for calculating a composite indicator that provides a comprehensive assessment and supports regional development monitoring. The research is based on the regulatory framework for cross-border cooperation and regional development and scientific publications in regional economics, spatial development and Euroregional integration. The methods applied include theoretical generalisation and grouping to systematise existing assessment approaches; formalisation, analysis and synthesis to develop the methodology; the analytic hierarchy process to determine the weights of criteria and indicators; comparative and statistical analysis to validate the proposed approach; graphical methods to visualise the results; and logical generalisation to formulate conclusions. A system comprising five main evaluation criteria and corresponding quantitative indicators was developed. A methodology for calculating a composite indicator of cross-border interaction effectiveness and the cross-border cooperation effectiveness coefficient was proposed. The approach integrates individual indicators into a unified assessment and enables comparison of cross-border cooperation performance. The results confirm the feasibility of applying the proposed methodology as a comprehensive tool for assessing cross-border cooperation and providing information and analytical support for regional development management. Further research should focus on refining the weights of criteria and indicators using expert assessment methods and validating the methodology across different border regions.
