Cement manufacturing accounts for approximately 7% of anthropogenic CO₂ emissions. To mitigate environmental impact and achieve “net zero” by 2050, developing cementitious materials that minimize cement consumption is crucial. This research aims to reduce cement usage in Foamed Concrete (FC). The study investigates the mechanical, durability, and thermal properties of FC using two distinct Supplementary Cementitious Admixtures (SCA): Glass Powder (GP) and natural zeolite. Cement was replaced with SCA at varying percentages (0%, 5%, 10%, 15%, 20%, and 25% by weight) in FC. The FC density was adjusted by incorporating foam at 15% and 30% of the total volume of concrete. The study evaluated the flowability of each mix in its fresh state. The mechanical properties were assessed by measuring compressive strength and ultrasonic pulse velocity. The performance of FC was further analyzed in terms of thermal conductivity, sorptivity, and water absorption. The test results revealed that FC with GP combinations exhibited high flowability and an improved strength-to-density ratio. Additionally, water absorption, sorptivity, and thermal conductivity were significantly reduced compared to conventional FC. An extensive cost-benefit analysis highlighted the feasibility of utilizing common waste materials to produce high-grade FC and assessed the impacts of cementitious admixtures as viable alternatives to cement. Doi: 10.28991/CEJ-2024-010-12-06 Full Text: PDF

This study investigates the influence of Bacillus subtilis bacteria on the strength and durability properties of M30 concrete with and without silica fume. The experimental study was conducted on four concrete mix series: conventional concrete (B1), conventional concrete with silica fume (B2), bacterial concrete without any admixtures (B3), and bacterial concrete with silica fume (B4). Silica fume was incorporated at replacement levels of 5% and 10% by weight of cement for the B2 and B4 mix series to evaluate its effect on bacterial activity and concrete performance. The study measured compressive strength, split tensile strength, and water absorption to assess mechanical and durability properties. Results reveal that bacterial concrete (B3 and B4) exhibits improved strength and durability compared to conventional concrete (B1 and B2). Furthermore, silica fume enhances the performance of bacterial concrete due to its pozzolanic action, which refines the microstructure and provides additional nucleation sites for calcium carbonate precipitation by Bacillus subtilis. Among all mixes, B4 with 10% silica fume achieved the highest strength and durability, demonstrating the synergistic effect of bacteria and silica fume. This research highlights the potential of bacterial concrete with silica fume as an innovative material for sustainable construction, offering improved mechanical performance and reduced permeability. Doi: 10.28991/CEJ-2025-011-05-013 Full Text: PDF

To realize the design of mixed-traffic railway lines, the choice of radius must ensure a comfortable ride for passenger vehicles, safe freight transport, and acceptable maintenance costs of vehicle wheels and railway infrastructure. This is not a straightforward task, and what is worse, there is a worldwide lack of clear criteria to limit the design parameters involved in the geometric definition of high-speed railway lines. The proof of this is the great number of technical standards (or recommendations) that are applied depending on the period of time, the administrations involved, or the technicians in charge. If the line is going to be aimed at mixed-speed traffic, this indetermination is even more severe, as the different type of trains that are forecasted to use the tracks (with different loads, speeds, etc.) should affect the limits of the design parameters. To begin to solve this problem, this paper aimed (1) to analyze the design parameters and limitation defined in several technical standards that are used to design high-speed railway lines, (2) to propose a graphical method for designing the horizontal alignment (the cant, the radius, and the clothoid), and (3) to apply the method to a real example to compare our proposed design with the original project for a case study in Spain.