Key Engineering Materials Vol. 986

Abstract: The Stable Isotope Unit of the National Centre of Scientific Research and the Ephorate of Kavala and Thasos collaborated on a project to investigate construction materials from the Ancient Theatre on Thasos Island, which was funded by NSRF European funds (2007-2013 and 2014-2020). Bulk samples of marble were collected to determine their provenance, technology, degradation features, and mechanical and physicochemical properties, with the ultimate goal of developing a conservation plan. By utilizing novel scientific techniques, the research team was able to date constructions discovered within excavations and establish remedial and preventive conservation plans using marble technology. The samples were characterized in terms of their isotopic, chemical, and mineralogical composition. Additionally, extended physicochemical and mechanical testing was applied to estimate the current condition of the Ancient Thasos Theatre. The ¹³C and ¹⁸O isotopic composition of the calcitic marbles was analysed to determine the environmental conditions during calcite formation, making it possible to define the marble provenance. Compositional and morphological analyses were achieved using energy-dispersive X-ray analysis by scanning electron microscopy, while the mineralogical phases were detected using X-ray diffraction and petrographic (polarized optical microscopy) analysis. Mechanical testing according to European Standards was achieved through the examination of compressive tensile strength and grain size distribution.

Abstract: Adobe homes are prone to natural phenomena such as floods, landslides, and earthquakes, due to the intense rains that occur from the month of November to March. This study aimed to investigate the mechanical properties of adobes reinforced with rice husk, lime and neem fibers and evaluate their compressive strength and water absorption capacity. The tests were carried out on adobes with dimensions of 10×10×10 cm3 made with earth, 0.75% rice husk, 0.75% lime and 1 to 3% neem fibers of the total weight of the adobe to determine the evaluations of the specimen. Therefore, a visit was made to the study area located in the province of Yauyos - Peru to classify the type of soil that would be used in the samples, then sift the soil to prepare the mud and let it rest for 24 hours. Then, incorporate the reinforcements and mold the adobes to let them dry for 28 days and proceed with the tests. The research recorded an improvement of 39 and 68% respectively on the strength of adobes reinforced only with rice husk and lime; and neem fibers after 28 days of drying with a proportion of 0.75% rice husk, 0.75% lime and 3% neem fibers. The absorption coefficient of adobes reinforced with rice husk, lime and neem fibers are between 16 and 27% better than adobes reinforced separately. Finally, this research will reduce the damage to homes caused by rains through the use of materials found in the localities and reduce pollution, thus creating a sustainable home with low costs for the inhabitants.

Abstract: Mineral sequestration technology is one of the most effective carbon capture and storage techniques. Basic oxygen furnace slag (BOFS), one of the by-products generated during the steelmaking process, has a particularly high potential for mineral sequestration compared to other similar wastes such as blast furnace slag and ladle slag. In the case of BOFS, mineral sequestration not only contributes to carbon uptake but also stabilizes its internal structure. So far, most of the investigations on BOFS mineral sequestration rely on accelerated carbonation involving high pressures and supplying concentrated CO₂ in a short period. Although these studies are useful for investigating the overall potential for carbon capture of BOFS, they are less useful for practical applications on a large scale. Moreover, it is hard to draw any conclusions regarding the carbonation reactions lasting for years in stockpiles of BOFS. This research identified the consequences of long-term carbonation on BOFS samples and determined the best conditions for natural mineral sequestration.

Abstract: Geopolymer, with its notable benefit of low carbon dioxide emissions, holds the potential to substantially curtail environmental pollution. According to the existing related research on geopolymer materials, it is obvious that it has great development potential in many engineering application fields, and it is a new generation of green and environmentally friendly recycled materials. Nowadays, there is a growing concern regarding explosion protection. Explosions near buildings can cause catastrophic damages on the building external and internal structure, and the most important thing is that can cause injuries and loss of life to the occupants of these buildings. This study investigates the mechanical performance of the fiber-reinforced geopolymer concrete under explosive testing. Furthermore, the finite element analysis models have been established through LS-DYNA software to simulate the explosive testing using Structure-Arbitrary Lagrangian Eulerian Method (S-ALE). The model is used to assess the dynamic mechanical behavior of geopolymer materials.

Abstract: The article provides an analytical review of the main problems and prospects for the use and introduction of polymer concrete in modern construction industries. It was found that due to high plasticity, low porosity and the ability to quickly gain strength, polymer concretes are used for the manufacture of decorative products of small architecture, structural load-bearing and decorative overhead parts, decorative paving tiles and paving stones, products for hydrotechnical purposes, etc. by methods of vibration molding and casting. The classification of polymer concretes used in modern construction industries is provided, as well as an idea of the properties of the most popular polymer concretes based on thermosetting polymers – furan, epoxy and polyester. The advantages and disadvantages of known polymer concretes and the main promising directions of implementation for the manufacture of building products and structures are given. Attention is focused on the influence of the qualitative and quantitative composition of polymer concrete, the nature of the thermosetting polymer binder, the type of fillers and aggregates, the terms of hardening, the degree of polymerization on the most important physical, mechanical and technological properties of the finished materials.

Abstract: An experimental study of the physical and mechanical properties of untreated and acetylated wood was conducted. The effect of acetylation on wood density was investigated. It was established that the density of the samples generally decreases after acetylation. As the level of acetylation increases, the fiber saturation point decreases in both conifers and hardwoods. Acetylation of wood helps to reduce the sorption properties of wood. The amount of swelling was analyzed. For untreated wood (aspen and alder), the volume swelling index is at the level of 7.5 %. Acetylation contributes to the stability of the geometric dimensions of structures, as the volume swelling index for aspen decreased by 4 times, for alder – by 2 times. An increase in the amount of swelling along the fibers is observed in all samples. Regarding the nature of the destruction of the samples during compression, the aspen (both untreated and acetylated) only crumples without visible signs of destruction. In some samples of alder, partial exfoliation is visible. It was found that acetylation has an ambiguous effect on the mechanical properties of wood of both species.

Abstract: The work is devoted to the study of magnesite influence on the strength properties of glued wood products with aluminosilicate adhesive. It they shown that the introduction of magnesite in the composition of aluminosilicate glue in the amount from 0.5 to 1.5 % contributes to an increase in the shear strength along the fibres by 1.57 times compared to the normative requirement (not less than 4 MPa). It we found that the bending strength of glued wood on a toothed spike is 1.4 times higher than the normative (not less than 26 MPa). After fire tests, no destruction of the glue joint on the spike we observed, and the bending strength of the samples increases proportionally to the introduction of magnesite in the glue composition. Water resistance of glue joints on the toothed spike when the samples we kept for 48 hours at the temperature 20 °С is higher than the standard value and increases with the increase of magnesite content in the glue composition. After boiling at the temperature 100 °С for 3 hours the samples containing 1.5 % magnesite meet the normative requirements (3 MPa).

Abstract: In this study, asphalt concrete (AC) mixtures were modified with polymerized sulfur, using PG58-22 bitumen, and crushed siliceous aggregate. Modifications involved replacing the base binder with 20%, 30%, and 50% polymerized sulfur, compared to a control mix with no replacement. The mixtures were subjected to Single Edge Notched-Beam (SE(B)) fracture tests under mixed mode (I/II) conditions with notch offset value of 48 mm, with temperatures ranging from 0 °C to -20 °C. These tests, focusing on the mixtures' response to mixed mode loading, provided load-displacement curves, enabling the determination of fracture energy. Results indicated an increase in fracture energy for 20% and 30% sulfur-modified mixtures. However, a trend towards increased embrittlement was also observed, as fractures occurred at lower displacements. Significantly, higher sulfur content correlated with similar or decreased mixed-mode (I/II) fracture energy, suggesting an improved resistance to low-temperature cracking for lower replacement percentages.

Abstract: Interlayer bonding within a multilayered pavement system plays an essential role in the overall performance of the pavement structure. Therefore, studying the interlayer shear strength (ISS) as a major index of the bonding strength and its accurate evaluation is of great importance. The main objective of this research is to assess the ISS of pavement using an experimental and statistically rigorous approach. The results showed that the ISS is highly temperature-dependent, experienced a rapid decline with increasing temperature. As tack coat rate increased, the ISS initially increased to reach a pick at 0.8kg/m² rate and then started to decline. The ISS demonstrated an almost linear correlation with vertical pressure at all temperature levels. Two-way factorial analysis of variance (FAV) underscored the significant impact of any two, namely temperature (T), tack coat rate (TC), and vertical pressure (VP), on ISS results. However, three-way FAV results indicated that the combined effect of T, TC and VP did not hold statistically significant influence on ISS. Moreover, all ISS models developed in this study were statistically significant at a 0.05 significance level, with a good coefficient of determination (R² =0.73) for multiple linear regression (MLR) and an excellent R² of 0.976 for polynomial regression (PR).