Materials Science Forum Vol. 968

Abstract: Arbolit concrete, as one of the types of light modern concretes, is a complex composite of a combination of different materials: a binder component, additives and cellulose aggregate. Wall blocks, panels, slabs, etc. are manufactured from arbolit concrete for the construction of low-rise residential, public, industrial and agricultural buildings. According to the properties, arbolit concrete is closest to the tree (organic aggregate is more than 85% of the volume). Arbolit concrete combines the best qualities of wood and concrete: environmental friendliness and durability of concrete, strength of wood and its vapor resistance. However, cellulosic aggregate has its own specific features that negatively affect the structure formation processes, in particular, the strength and durability of the composition “ organic aggregate - astringent "to moisture-variable effects. Selection of a binder for arbolit concrete is also a difficult task that requires a separate research. Basically, for the manufacture of products made of arbolit concrete portland cement is used, abroad - lime binder. The disadvantage of cement concrete on cement, lime and lime containing a binder is a relatively long period of gain of brand strength. A promising direction for solving this problem is the use of composite gypsum binder for the production of concrete. Based on the above, we can conclude that the design of low-density arbolitbeton formulations on a composite gypsum binder is an urgent task [1].

Abstract: In modern construction, a large variety of small architectural forms are used, for the production of which cement concrete is traditionally used, which should have improved physical and mechanical properties and decorative properties, while having a low cost. Improvement of these properties is achieved through the use of carbonate additives - highly dispersed chalk. Experimental results show that the addition of highly dispersed chalk affects the structure of cement stone, which is represented by low-base hydrosilicates, calcium hydrocarbonate and complex compounds that create a dense structure, which reduces the permeability of the material for corrosive media. It is assumed that the addition of highly dispersed chalk improves the elastic-plastic properties, increases the crack resistance, which provides high performance properties of concrete.

Abstract: The effect of mineral filler compounds on vapor permeability and hygroscopic properties of water-based polymer dispersions and the possibility of their use as decorative and protective material for stucco facades finishing was studied. According to Facade Protection Theory (H.M. Künzel), the assessment criterion was vapor permeability and water vapor diffusivity. The pairwise correlation of building physical properties of water-based polymer dispersions in the coordinates of Künzel's diagram clearly demonstrates that, in terms of hygroscopic, all the samples studied correspond to the low hygroscopic class, and in terms of vapor, they are close to high water vapour diffusion rate class.

Abstract: Study of rheological properties of concrete mixtures based on modified cement systems in order to determine process parameters. Methodology. To study structural-mechanical properties of modified concrete mixtures of different consistency at their horizontal vibrating displacement an oscillatory viscometer was designed. Results. The optimization of the process of vibration displacement of concrete mixtures with the specification of parameters of vibration impacts taking into account structural-mechanical properties of the mixture is performed. It has been established that the viscosity of the modified cement system of the concrete mixture is a variable quantity, which depends on the parameters of the vibration impacts. Scientific novelty. The mechanism of interaction of the modified concrete mixture with the form and the table vibrator during its vibration compaction is determined. On the basis of this, a model of concrete laying process control is proposed, that allows to predict the ability to form a dense concrete structure. Practical significance. Disclosed physical nature of the process of vibrating displacement of modified concrete mixtures using the principles of physical-chemical mechanics of concrete allows reasonably choose the best options for vibration impacts.

Abstract: Concrete of used sewers is exposed to various aggressive environments. While making concrete pipes for special purposes, special attention is paid to reducing the permeability of the surface layer of concrete. It is possible to increase the operational characteristics of concrete by introducing into the cement system the active components chemically interacting with the cement minerals. When the complex modifier interacts with cement particles, the structure and properties of the modifier undergo qualitative changes. The article presents the results of researching the porosity of the modified cement matrix. It has been established that in the neoplasms of the modified cement matrix of concrete, the quantity of free calcium hydroxide does not exceed 5% that is a necessary condition for getting a corrosion-resistant material. As a result of the analysis of modern technologies, it has been established that physical modification is possible by removing excess mixing water that increases the use of the potential qualities of cement in order to increase the density, impermeability and strength of concrete in the process of compaction of the mixture.

Abstract: Alkali hydroxide and alkali salt possessing high solubility are considered to be one of main reasons for efflorescence occurrence in exterior walls of buildings made from solid masonry units. Analysis of alkaline attack on efflorescence processes in the surface of exterior walls of buildings is presented herein. Volumetric changes in solid phase materials in the course of alkali hydration and carbonation reactions under efflorescence are calculated by the proposed procedure. The indicated processes are confirmed by laboratory simulation and by field studies of ceramic block and lime brick masonries, and vibropressed concrete blocks within the Republic of Bashkortostan.

Abstract: This paper presents the research method of hardening process of gypsum binders and composites, based on them, using the ultrasonic method. Modern construction composites, based on higher water resistance gupsym, contain the coarse aggregate particles, giving them heat and sound insulating properties. One of the frequent purposes, designing such composites, is the slowdown of the processes of setting, so it allows the builders to work with the material for a sufficiently long period. The use of standard control penetration methods of the setting processes for the considered composites becomes difficult because of the presence of course particles in the binder paste. The ultrasonic method is proposed to use alternatively to study the process of setting. For its implementation, the technique has been developed, based on the use of ultrasound systems for quality control of concrete products. The transit time of ultrasonic signals through the layer of hardening binder paste with the fixed thickness was measured in a regular intervals until completely setting. On the basis of the obtained data, the ultrasound velocity was calculated and the setting time was determined. For this purpose, a differential curve of the time of ultrasound transmission was plotted, and the period was considered, at which the transition to the steady-state condition was carried out, it is equivalent to the end of the setting. The initial setting was determined by the first trip of the measuring equipment, corresponding moment of the formation of the primary crystal structure of the composite, which has sound-transmission properties. To verify the values of the setting time, the simultaneous measurement of the plastic strength of the model system was used. The moments of the beginning and the end of the setting, as well as the ultrasound velocities which were typical for these moments, were determined with the plastic strength. The obtained velocity values allowed to find the setting times of other composites. The actual setting time is estimated based on the values, obtained by all the available methods. The model, based on percolation theory, has been proposed for analyzing the physicochemical phenomena during the setting.

Abstract: The paper represents a formalized methodology for solving the problem of creating fundamentally new materials, such as "base - coating" ones, which have increased surface wear resistance and relatively high strength and viscosity. Electrospark alloying (ESA) method is proposed as a process for depositing protective coatings on metal surfaces. There are considered the issues of improving the quality of the coatings formed by the ESA method. There is specified a feature of processing the surfaces having been treated with the use of the ESA method, which feature being associated with a relatively small thickness of the layers formed (tens of micrometers). Since to reduce the roughness of the surface, the process of grinding is difficult or even unacceptable to perform, it has been suggested to use the method of surface plastic deformation (SPD). One of the effective SPD methods for finishing the parts is a diamond smoothing process, which, in contrast to running-in with a ball or roller, allows processing the parts of very high hardness values. As a reserve to improve the quality of coatings formed by the ESA method, there is considered a process for producing combined electrospark deposition coatings (CEC) with hard wear-resistant and soft anti-friction metals integrated therein. There are represented the results of mass transfer process investigation performed at forming the CEC on the specimens of steel 45 with indium, tin and copper being used as soft antifriction metals, and tungsten and hard alloy of VK8 grade applied as wear-resistant materials. There is represented a mathematical model for calculating the main ESA technological parameters being necessary for forming the CEC and allowing to predict the weight gain (increase in weight) and size gain (increase in size) at the cathode (the part). It allows predicting the CEC main technological parameters for any electrode pair materials (substrate material and electrode materials making up the CEC).

Abstract: There are shown studies on influence of film-forming components on the corrosion resistance of powder coating. Protective and decorative powder coatings - one of the most promising types of paints and varnishes for industrial use. Their main advantages are: absence of solvents, practically waste-free coating technology (the degree of powder utilization during application is close to 100 relative simplicity and cost-effectiveness of the production process of coating. The study of protective properties of powder coatings is associated with the detection of high performance properties and high corrosion resistance of the material. Although corrosion resistance of powder coating performance continues to improve via the design of more effective film-forming components the nomenclature of which is wide enough.

Abstract: Among physical and mechanic properties of coatings the internal stresses are of special interest. Internal stresses include stresses which exist and are counterbalanced within a rigid body in cases when there is no external action which caused them. In coatings obtained on the basis of nickel, chrome they can decrease the adhesive strength, cause cracking, peeling, anticorrosion properties deterioration. But the definite level of internal stresses leads to increase of hardness and coatings wear resistance and also facilitates porous coatings obtaining. The results of theoretical and experimental investigations of the internal stresses that appear in oxide ceramic coatings formed by plasma-electrolytic oxidation (PEO) on aluminum surfaces are presented.