Materials Science Citation Index

This article is devoted to the study of the clay material modification with a natural polymer (starch). Authors given the assessment of starch thermal modifications, as well as their effect on the clay composite. Described the technology of a retrograded starch hydrogel (RSH) preparation. Investigated the influence of various RSH concentrations (2,5%; 5%; 7,5%; 10%) and its thermal conditions (150 °C for 3 h. and 5 h.) on the mechanical properties and structure of the clay composite. The experimental results showed that the clay strength tends to increase up to 74% with the increase of starch retrograded hydrogel concentration and its heat treatment time. It was found that the addition of RSH made the structure of the clay composite denser (bulk density increased up to 2,5%; shrinkage reduced for more than 1%). This modification method is very promising, since it combines both environmental friendliness and high mechanical properties of the final clay material.

A numerical study of the interaction of the virus with the cell is presented. The cell was selected for human circulatory endothelium, while the virus was selected close to SARS-CoV-2. The environment in which the virus interacts is close to the blood. A numerical experiment of the interaction was carried out using the DEM. The result is an interaction process showing a change in force, displacement, velocity over time. Under various initial conditions, the analysis examines the influence of spikes and drag forces for the interaction of the virus with the cell.

The interaction of the virus with the alveoli cell is examined, where the virus enters the lungs through the human airways after human inhalation. The virus selected was close to SARS-CoV-2. The numerical experiment was performed using the discrete element method. The results show the change in force, velocity, and displacement over time. The model evaluates the interaction of the capsid and spikes with the alveoli cell surface. The initial parameters, such as initial velocity, size, and data required to describe the interaction, were selected based on known physical experiments. The mechanism of energy dissipation associated with adhesion is considered.

The paper deals with the process of binding of two nucleotides, which is considered part of a more complex process, such as the transfer of telomerase to the telomere region of chromosomes during cell division. The binding process is evaluated using the originally developed attraction-related energy dissipation mechanism. Energy dissipation has also been observed using a viscous damping model. Viscous damping is considered to obtain dissipative oscillations during the interaction of nucleotides, which can be part of the binding process. The work presents the dynamics of nucleotides, indicating the values of force, distance, velocity for a certain period of time.

Looking from the mechanical point of view the suspension containing the bacteria may be considered as a system of living active ultrafine particles. Here a model is developed for the interaction of the bacterium in an oblique direction during contact. The model considers an adhesive bacterium moving through a fluid, acting with appropriate specific forces, such as steric, electrostatic double layer and hydrodynamic forces. To understand the influence of the latter hydrodynamic forces on the bacterium, numerical experiments using DEM are carried out with this force and without it. A comparison of these two cases shows the difference in movement.

The main objective of this research is to develop high-strength concrete mixture (compressive strength ≥ 41 MPa) that is resistant to fatigue and suitable to produce slabs for modular pavements also known as precast concrete pavements. In addition to this, other characteristics (compressive strength, flexural strength and indirect tensile strength) were determined as well and the effect of fibers depending on type and amount in the presence and absence of silica fume has been revealed. Silica fume (0% and 7% by cement mass) and three types of fibers (one type of steel fibers and two types of polypropylene fibers) with three different amount of each fiber type were used to produce concrete mixtures. At all, 20 concrete mixtures were produced and tested in terms of static and cyclic bending, static compression and static tension. The research showed that the use of both fibers and silica fume in the concrete mixture leads to the best performance and steel fibers are superior to polypropylene fibers. Concrete mixture with 49.5 kg/m3 of steel fibers and 7% of silica fume by cement mass had compressive strength of 61 MPa and the highest resistance to fatigue and thus is the most potential to produce slabs for modular pavements.

The application of low noise pavement is one of the most effective solutions to reduce tire/pavement noise. Low noise pavements are achieved by using asphalt mixtures with a high air void content (e.g., porous asphalt). However, these material have relatively low durability. Therefore, to ensure sufficient durability and long-term acoustic properties, low noise asphalt mixtures must be designed considering both acoustic and climatic conditions. The main objective of this study was to design four semi-dense asphalt mixtures (2 stone and mastic asphalt (SMA) mixtures and 2 asphalt mixtures for very thin layers (BBTM)) with increased air void contents (>10%) that absorb tire/pavement noise and are resistant to traffic and climate conditions. Large-scale laboratory testing was performed to evaluate the acoustic properties as well as the effects of traffic and climate conditions on the performance of the designed asphalt mixtures. These tests revealed that modified BBTM asphalt mixtures have better sound absorption properties than modified SMA mixtures but are less resistant to rutting, have lower stiffnesses and indirect tensile strengths and exhibit higher mass loss after freeze-thaw cycles. The most promising asphalt mixture was identified by a developed analytic hierarchy (AHP). The BBTM 8 mixture is the most rational solution for low noise pavement.

Chloride ion penetration can cause corrosion of steel embedded in concrete in chloride-laden environment. Investigating the model of chloride diffusion is of vital importance to durability assessment and residual service life prediction of concrete structures. In this paper, firstly, a calculation method of instantaneous chloride diffusion coefficient (Dins) is established based on the apparent chloride diffusion coefficient (Da). Then, the existing experimental data in the literature are used for studying the influence of the coupled time and concrete stress effects on Dins, and the theoretical model of Dins is established. Finally, based on the established model of Dins, a prediction model of chloride concentration is proposed and the model is validated by two sets of experimental data. By comparative study with experimental data, the results show that the calculation method of Dins is reasonable and feasible, and Dins is smaller than Da at the same exposure time. Generally, the relative error between Dins and Da increases with the exposure time under the same tensile or compressive stress level, while at the same exposure time, it first increases and then decreases with increasing concrete tensile stress level, whereas it decreases with increasing concrete compressive stress level. It is found that Dins has strong time and stress dependence. The computed results of the proposed chloride ion concentration model agree well with the experimental data.

The paper analyses the effect of waste sludge from paper industry (paper sludge) on physical and mechanical properties of clay bricks, their microstructure and resistance to freezing and thawing. Paper sludge is not hazardous industrial waste mainly consisting of cellulose and calcite. Clay bodies were made from the mix containing from 5% to 20% of paper sludge and fired at 900 °C and 1000 °C temperatures. Open pore structure in the clay body is developed as a result of burnt cellulose fibres and calcite decarbonization. Physical and mechanical properties of clay bodies change depending on the content of added PS: shrinkage, density and compressive strength reduce, water absorption and effective porosity increase. It is recommended to add 5% of paper sludge to the clay body and fire it at 900 °C temperature, or alternatively add 5–15% of paper sludge and fire the clay body at 1000 °C temperature. In terms of resistance to freezing and thawing, such products are regarded as frost resistant in moderately aggressive environment, i.e. in structures protected from direct environmental effects.

Oxygen diffusion and oxidative reaction are two main factors in asphalt oxidative aging discovered by experiment, but the dynamic balance between them could not be easily studied by experimental methods due to its comprehensiveness. A pavement oxidation model was utilized to simulate this process in asphalt: oxygen molecules penetrate into the asphalt film and then react with the asphalt molecules. In some special cases, diffusion or reaction can become the determination step of asphalt oxidative aging. Another factor, asphalt hardening, which is a result of oxidative reaction, slows the oxygen diffusion seriously and consequently. With the help of the model simulation, the efforts of binder reaction kinetics, hardening properties and temperature on this balance have been studied and discussed in detail. A new standard for asphalt binder, solely from oxidation aspect, includes high activation energy, low hardening susceptibility and high hardening intercept. A new idea of anti-oxidant development was proposed. By decreasing oxygen diffusion, asphalt oxidation can be slowed down, but only works for oxygen diffusion determined cases.