Andrei Burlacu

Industrial applications in the concrete industry face significant challenges in selecting appropriate metallic materials, as these choices can enhance equipment lifespan and reduce costs. This study examines the corrosion behavior of various metallic materials, offering valuable insights for their selection in corrosive environments. The findings indicate that material testing can provide cost-effective solutions for concrete industry equipment. Notably, replacing cast iron used in concrete mixing blades with specific steels is advantageous for corrective or accidental maintenance, lowering spare parts costs, and short-term use, steels P265GH and AISI 4140 exhibiting corrosion resistance similar to cast iron. Additionally, for mineral aggregate dryers, selecting adequate steel can significantly reduce operating and maintenance costs while increasing equipment durability. The results show that substituting steel S235 with steel P265GH can decrease the corrosion rate by nearly 65%.

Mixers used in the production of cement concrete operate under special conditions such as mechanical stresses, abrasive–erosive friction phenomena, and corrosive working environments. In this paper, the authors aimed to establish a correlation between the chemical composition of mixer blade materials and their wear behavior. Three types of alloyed (chromium) cast iron were used for an experimental program that included three sets of tests in accelerated wear conditions which replicated the actual working environment (mixture of mineral aggregate, sand, cement, and water). The tribological tests were carried out using a Baroid tribometer. The results indicated that regardless of the test environment, cast iron with the highest chromium content exhibited the best wear resistance. However, it cannot be concluded that the wear resistance of the studied cast iron materials increases as a direct result of an increase in chromium content. For a chromium content of less than 25%, a better tribological behavior was observed for cast iron with a lower chromium content (of about 4%) than for cast irons with a higher chromium content (of about 9%).

Thedistribution of aggregates in the cross-section of the drum, in the case of equipment used for the production of asphalt mixtures, essentially influences the performance of rotary dryers. In the research carried out in this article, the optimization of the distribution of particles in the active region of the drum was pursued by modifying the geometric shape of the flights, taking into account at the same time the influence of the technological parameters of operation such as drum rotation speed and drum filling degree. The studies were performed using the discrete element method (DEM), and the obtained results revealedthat flight geometry strongly influences drying efficiency. The efficiency of rectangular double-angled type flights is strongly influenced by the drum rotation speed, especially at high levels of filling degree (20%), with the mass of aggregates exposed to drying increasing by 41.11% when drum rotation speed increases from 10 rpm to 15 rpm. Similarly, hook-type flights show a minimum efficiency at 15% filling degree and 15 rpm. The comparative analysis of the flight shape is not only carried out in order to establish the variant that ensures maximum drying efficiency but also from the point of view of execution technology. (Original flights can be obtained by deep drawing, but they have a complex geometric configuration; cup flights can be obtained very easily from tubular material cut on the generators; hook flights by deep drawing or welding the cut tubular material on a straight plate, and the L type by deep drawing). Taking into account that semi-finished products can be very thick, it is possible that, in some cases, hot embossing is necessary, so making them out of tubular material eliminates these inconveniences. All the presented results highlight that the rectangular, double-angled and hook-type flights are the most appropriate shapes that can be used regardless of the drum filling degree and rotation speed.