Key Engineering Materials Vol. 1035

Abstract: Composite elastomer-cable tractive elements can be used in mine hoisting, conveyor transportation, or as stay ropes in permanent structures. The working conditions of a rope depend on the application of a machine where it is used. Composite rope design provides particular advantages in industrial utilization of ropes, however raises the issues of predicting their stress state and reliability during operation in various loading conditions. Article purpose is in determining a dependency of stress-strain state of a composite elastomer-cable tractive element on a breakage (breakages) location scheme of reinforcing elements. Article methodology is in analytical solution of a model using methods of mechanics of layered composite materials with layers of increased rigidity connected by elastic layers. Mathematical models of a stress-strain state of composite elastomer-cable tractive element on breakage (breakages) location scheme of reinforcing elements are formulated and dependencies are established. The scientific novelty of the article is in establishing that extreme values of stress-strain states indicators of butt joints for a step-like scheme do not depend on the amount of cables in a rope, provided that there are at least six cables. In case of breakages in continuity of several cables, in several cross-sections, edge disturbances are localized both along the length and in adjacent cables. Tangential stresses in a rubber layer of a butt joint for a step-like scheme take place, practically, only in the rubber located between the discontinuities of the adjacent cables. Qualitative character of dependencies of tangential stresses coincides with a character of distribution of tensile forces in cables. At the same time, the largest internal forces and stresses in a butt-joint connection for a step-like scheme occur in the corresponding elements closest to belt edge. Practical significance of the article is in that a force concentration coefficient in butt joints for a step-like scheme is established. The established feature of a dependency of tensile forces of side cables and stresses in an elastic material that connects it to the adjacent one in the butt joint for a step-like scheme indicates a possibility to ensure a condition of equality of safety margins of an elastic interlayer and the most loaded cables, by selecting the lengths of the side cables in the connection. The actual loads acting on the lifting mechanism and the parameters of the lifting system can be taken into account when setting the boundary conditions for solving the models suggested in the article.

Abstract: The current experimental study aims to confirm some critical conclusions of the preliminary research regarding the possibilities of valorizing the residue material generated the Abrasive Water Jet (AWJ) procedures for industrial material processing, namely the Spent Garnets (SG), by innovatively integrating them in cement-based materials (mortar and concrete) and further on, in construction-eco products (paving pre-cast units, road construction, concrete for structural or non-structural elements, etc.). The use of SG wastes is considered as partial substitution of fine aggregates (sand) in cementitious materials, simultaneously offering the possibility of reducing the use and exploitation of aggregate, as limited natural resource. The methodology consists in developing a regular mortar mix, the Reference (R), on which several substitution percentages were applied with respect to the natural sand quantity, by Spent Garnets (SGs) provided by local producers. The substitution percentages initially ranged from 10 to 50% with respect to the Reference mix, as specified by recent, international studies, and they were also used in the preliminary evaluation, as well. Further on, the relevant substitution percentages were established as 30% and 50% values, and the corresponding mortar mixes were realized. The specific comparative analysis was performed in terms of mechanical performance at early age (7-day mechanical strengths) and also at 28 days. The obtained results are validating the initial results, proving the consistency of the previous conclusions and encouraging the use of SG wastes in cement-based construction materials. Complementary studies are further on considered and prepared, focused on using SGs as aggregate partial replacement in pavement eco-blocks, due to their high demand on the construction market.

Abstract: This study examines the influence of the structural type of bitumen and its consistency on deformation behavior under low-temperature conditions, focusing on the glass transition temperature range, which is critical for the design of frost-resistant asphalt pavements. Motivated by the challenge of low-temperature cracking – a primary cause of asphalt pavement deterioration in cold climates – the research addresses the need to enhance bitumen’s stress relaxation capabilities to mitigate thermal cracking and extend pavement lifespan. Bitumen samples of gel, sol, and sol-gel structural types with different penetration grades (35/50, 100/150, and 160/220) were tested for creep compliance under axial tension at temperatures from -40 °C to 0 °C. The results showed that gel-type bitumen exhibit significantly higher creep compliance compared to sol-type bitumen with the same penetration, indicating better deformability. Specifically, gel-type bitumen demonstrated a plasticity index (m-value) 1.5–1.7 times higher than sol-type bitumen in the range from -40 °C to -30 °C, reflecting enhanced stress relaxation. The glass transition temperature of gel-type bitumen was found to be 4–6 °C lower than that of sol-type bitumen, further supporting its suitability for cold climates. These findings provide quantitative insights into optimizing bitumen selection for frost-resistant pavements, offering a creep compliance testing method that is simpler than traditional BBR and DSR approaches. The results are significant for improving pavement durability in regions with extreme temperature fluctuations, reducing maintenance costs, and guiding the development of performance-graded bitumen specifications.

Abstract: Ambient vibration instrumentation is a non-destructive in-situ testing method that can be used to assess the dynamic properties of a building. By analyzing the time histories of accelerations, velocities and displacements (both instantaneous maximum values, or averaged RMS values) and applying specific evaluation criteria, we can estimate the extent of any potential damage. In 2016 and 2021, the ISIM Timisoara building underwent in-situ testing through ambient vibration measurement, using different sensor placement schemes (horizontal, vertical with an external sensor, and sensor at the last level), to accurately characterize the complex structural system. Furthermore, an analysis of the interaction between the structure and the soil is also provided. The approach outlined in the article assists in evaluating the national-level vulnerability of the built environment.