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RAR RUS 12101-12101 Qais Qais Abdurrahman Ali Kotlyarevskaya Alena Valerevna Okolnikova Galina Erikovna Al-muradi Yunes Ali Ali Thermo-mechanical evaluation of hybrid basalt fiber aerodrome concrete pavement under dynamic impact The object of research is the thermo-mechanical behaviour of hybrid basalt fibre-reinforced concrete used in aerodrome pavements. The subject of the research is the effect of hybrid fibre composition on impact resistance and thermal durability under dynamic loading. The purpose of the research was to develop and assess a hybrid basalt fibre mix capable of enhancing the mechanical and thermal stability of airfield pavements. Method. Three concrete mixes were selected: a control mix (K, 0% fibre), a micro-fibre mix (2A, 2% micro-fibre), and a macro-fibre mix (2B, 2% macro-fibre). The mechanical properties, specifically the Modulus of Elasticity, were modelled as a function of temperature and using reduction factors based on existing building standards (Eurocode 2: EN 1992-1-2). A linear static analysis was performed for 12 cases (3 mixes, 4 temperatures) using Autodesk Robot Structural Analysis software. The pavement was modelled as a slab with elastic soil supports (Winkler foundation). Two cumulative load cases were applied: a static uniform pressure of over an area and a uniform temperature increase. The primary output parameters were Total Displacement and Maximum Bending Moment. Results. The results indicate that high temperature is the most governing factor in the slab's structural behaviour, causing a varied reduction in material stiffness. This thermal degradation led to a gradual and dramatic increase in maximum vertical displacement, which rose from a baseline of at (Mix K) to at across all three mixes. Crucially, at high temperatures, the reinforcing action of both micro- and macro-basalt fibres was rendered insignificant because the failure mode was completely governed by the thermal degradation of the cement matrix itself. The maximum bending moment exhibited a non-linear relationship with temperature, initially decreasing due to stiffness loss, but then increasing sharply at (to for Mix K) due to significant thermal stresses and warping effects, indicating a state of critical distress. 10.4123/CUBS.121.1 69 Hybrid fibre-reinforced concrete Thermo-mechanical analysis Aerodrome pavements Finite element analysis Elevated temperatures https://unistroy.spbstu.ru/article/2026.121.1/ 12101.pdf

RAR RUS 12102-12102 Chernykh Tamara Nikolaevna Komelkova Maria Vladimirovna Wu Chuangzhou Gorbachevskikh Kirill Alekseevich Gilevich Anton Anatolevich Orlov Aleksandr Anatolevich Shape memory polymer rods for improving crack resistance in reinforced concrete beams The object of research is reinforced concrete beams with combined reinforcement. The improvement of their crack resistance is essential because crack propagation reduces the durability of structures, and conventional methods of crack closure are not always effective. Method. The study employs an experimental method involving four-point bending tests on specimens with additional heat-activated polycaprolactone rods. Results. The study found that after heat activation, the crack width in the modified beams was more than halved compared to control specimens, and the deflection value decreased by 16%. These results demonstrate the potential of using shape memory polymer elements to control the deformation state of reinforced concrete structures and improve their performance. ***ARTICLE IN PRESS*** 10.4123/CUBS.121.2 69 Reinforced Concrete; Self-healing; Deformation; Bending Tests; Concrete Beams And Girders; Shape Memory Polymers; Reinforcement https://unistroy.spbstu.ru/article/2026.121.2/ 12102.pdf

RAR RUS 12103-12103 Qais Qais Abdurrahman Ali Kotlyarevskaya Alena Valerevna Okolnikova Galina Erikovna Hybrid basalt fiber aerodrome concrete performance evaluation Concrete airport pavements are subjected to severe mechanical and environmental demands, necessitating improved crack resistance, fatigue performance, and durability. The object of research is macro–micro hybrid basalt fiber reinforced concrete (BFRC) as a potential high-performance pavement material. The work aims to evaluate the influence of basalt fiber dosage and hybridization on crack width and depth, fracture toughness, fatigue life, chloride ingress resistance, and structural reliability. Method. Mechanical properties from laboratory tests were integrated with semi-empirical fracture mechanics models, S–N fatigue relationships, Fick’s second-law chloride diffusion analysis, and reliability-based statistical assessment. Results. Results indicate that increasing fiber content reduced predicted crack width and depth, while hybrid systems significantly enhanced fracture parameters. The 1.5A0.5B mix exhibited the highest fracture toughness and durability performance, whereas the 2A1B mix demonstrated superior fatigue life and reliability index. Overall, balanced hybrid basalt fiber systems provided synergistic improvements in cracking resistance, fracture behavior, fatigue performance, and long-term durability for airport pavement applications. 69 Basalt fiber Crack Durability Fatigue Fracture toughness Fiber hybridization https://unistroy.spbstu.ru/article/2026.121.3/ 12103.pdf

RAR RUS 12104-12104 0000-0002-4590-8552 Ehsani Armin 0000-0001-5939-3257 Nasimi Shahin Shambina Svetlana Lvovna 0000-0002-7168-5786 Gebre Tesfaldet Hadgembes Bond strength between concrete and steel rebar in circular sections The object of research. This research seeks to gain a deeper understanding of the mechanisms of force transmission between concrete and steel rebars in circular sections and to provide practical solutions to improve the performance of the structures. The bond strength between concrete and rebar in circular sections has been extensively studied due to its significance in the design and evaluation of reinforced concrete buildings. Compared to other building types, concrete structures are used notably more often, to the extent that most countries in the world are using more concrete than steel. Due to the significance of steel-concrete adhesion and how it affects the behavior of reinforced concrete elements, a thorough investigation into all the factors influencing this adhesion and how they relate to one another is required. In reinforced concrete constructions, steel-concrete adhesion is very crucial and is influenced by the concrete mixing strategy as well as the shape and positioning of the steel. Method. The out-pull test is one of several tests used to determine the adherence between concrete and steel. This study used the pull-out test with three tests to examine the effects of the length of the rebar buried in concrete, the amount of concrete coating on the rebar, and the 28-day compressive strength of concrete on the adhesion between concrete and steel. Results. With the increase in the length of the reinforcement inside the concrete sample, no noticeable changes are observed in the average maximum adhesion stress. According to several experimental studies on the bond strength of concrete and rebar in circular sections, the average maximum adhesion stress rises with the concrete sample's diameter. Additionally, the average maximum adhesive stress rises with an increase in the 28-day compressive strength. ***ARTICLE IN PRESS*** 10.4123/CUBS.121.4 69 Compressive strength Adhesion strength Pull-out test Adhesion between steel and concrete Reinforced concrete https://unistroy.spbstu.ru/article/2026.121.4/ 12104.pdf