Materials Science Forum Vol. 1011

Abstract: Concretes with frame structure produced by using the technology of separate concreting by immersing a coarse aggregate in a low-viscosity mortar matrix due to an increased concentration of coarse aggregate have an increased E-modulus, reduced creep coefficient and cement volume in concrete compared to traditional vibrational compaction concretes. Production concrete using separate concreting technology by immersing a coarse aggregate in a mortar matrix with low-viscosity allows to obtain a frame structure of concrete with a concentration of coarse aggregate up to 0.7 when a voidness of coarse aggregate is equal 0.28. The real concentration of coarse aggregate in a concrete structure depends on the particle size of the coarse aggregate, the cross-section dimensions of the structure, and the reinforcement coefficient. The influence of geometric dimensions and the coefficient of reinforcement on the concentration of coarse aggregate in the concrete with frame structure is studied. The concentration of coarse aggregate decreases with the growth of the S/V modulus (S – area, m², V – volume, m³) and the reinforcement coefficient, but the decrease in the E-modulus does not exceed 5%. Conclusion: regardless of the type of construction and reinforcement, the concrete of the frame structure must have a sufficiently high uniformity of deformation properties.

Abstract: In order to determine the inhibitory additives concentration influence degree on the corrosion degradation rate, we studied the anode behavior of steel reinforcement made of steel grade St3 in a 10% solution NaCl with and without the inhibitors additives of various concentrations. As inhibitory additives, nitrates of potassium, sodium, magnesium, calcium and zinc were introduced into the aggressive environment, since they are often introduced into concrete compositions to accelerate their hardening. Polarization curves have been obtained for steel reinforcement in an aggressive environment, allowing the corrosion rate calculation. It was established that the introduction of potassium and zinc nitrates in an amount of 0.5% into an aggressive environment has the greatest effect on the corrosion processes’ inhibition. When nitrates of alkali and alkali-earth metals are introduced into an aggressive environment, the change in the reinforcing bars mass made of St3 steel occurs 7-8 times slower. Increasing the concentration to 1 and 1.5% is shown to be impractical, due to the small difference in the effect on the reinforcing steel anodic dissolution. A study on the effect of combining inhibitory additives on the corrosion resistance of steel reinforcement in a 10% solution NaCl was made. It was found that the combined action of inhibitors is less effective than the single effect of additives on the corrosion rate.

Abstract: The results of the scientific research and pilot tests on the production technology of soft molded ceramic bricks based on siliceous opoka-like rocks are presented. A description of soft-molded brick, which is distinguished by a huge variety of appearance and unusual design, which has earned recognition from architects and designers, is given. It is emphasized that the main limiting factor for the wide distribution of this type of brick is its high cost, due to the very small volumes of its production in Russia. It is indicated that the current situation poses a very difficult and urgent task for the wall ceramics industry - to establish the widespread production of soft-molded bricks, which in addition to the aesthetic properties will have the good operational properties. The opoka-like rocks’ characteristics and the results of studying their ceramic properties in relation to the technology of soft molding are given. The classification of the soft molded brick front surface types is presented for discussion. The main technological parameters of production, the relationship and the influence of various technological factors on the properties of the products obtained, as well as the mechanism for forming the structure of the calcined products are determined. A variable technological scheme for the production of soft molded ashlar brick has been developed. It is emphasized that the presented research results will be of interest to a wide circle of the molded ceramic bricks’ manufacturers and will help to establish the wide production of soft-molded bricks in Russia.

Abstract: The influence of the glass powder dispersion and its amount on the operational properties of glass-reinforced concrete is investigated. Box and plate glasses, which were crushed and ground in a ball mill, were used as the starting material. Portland cement manufactured by Serebryakovcement, a brand of CEM IIA 42.5N, was used as a binder. The developed technology for the glass-reinforced concrete manufacturing provided at the final stage for a joint grinding of Portland cement and glass powder. At the same time, the specific surface area of ​​Portland cement increased from 3200 to 6500 cm²/g. The optimum amount of fine glass powder in glass-reinforced concrete is established. It is shown that at the content of 30 wt.% glass powder with a dispersion of 5872 cm²/g the glass-reinforced concrete density is 1915 kg/m³ and the compressive strength is 45.09 MPa. When superplasticizer is introduced into glass concrete, a synergistic effect is observed, as a result of which the compressive strength increases to 50.88 MPa. Using the synchronous thermal analysis, the effect of finely dispersed glass powder on phase transformations in glass-reinforced concrete under non-isothermal heating conditions was studied. It was shown that the processes of ettringite dehydration in glass-reinforced concrete are shifted to the region of high temperatures, and the processes of calcium hydro silicates dehydration and calcite destruction are shifted to lower temperatures.

Abstract: A detailed theoretical analysis of the processes occurring in foam concrete mixtures in the period between their laying in the mold and the phase transition “from viscous to solid” completion moment. The stages of the formation of inter-pore septa in foam concrete mixtures, depending on the material nature and shape of the solid dispersed particles of raw materials, are sequentially considered. It is shown that their shape affects the mass transfer rate and the density of inter-pore septa during the structure formation. The reasons for the fluctuations in the elasticity of foam films during the predominance period of viscous bonds between the components of the raw material are described. The gas inclusions factors of influence on the dispersion parameters and, as a consequence, the aggregative stability of foam mixtures, are ranked. The positive dispersed reinforcement effect on the mass transfer processes in mixtures and the hardened concrete strength is substantiated.

Abstract: The results of selection and principles of calculating the ceramic masses composition for the clinker tiles’ production from argillites taking into account the raw materials’ characteristics are presented. The positive properties of argillites, as well as the properties that do not allow the tiles’ production of by stamping, which is traditional for these products’ manufacturing, are noted. Having low sensitivity to drying, low air shrinkage, high strength of the calcined shard, while being fusible sintering raw materials, argillites are low plastic and have insufficient bonding during molding, which indicates the need for corrective additives. In this work, the task to select the composition of ceramic masses to increase the plasticity of argillites while maintaining the positive properties of the main raw material was set. The authors proposed the use of siliceous clays as a corrective additive. An integrated approach was applied in calculating ceramic masses by grain composition and chemical and mineralogical indicators. Based on the research of A.I. Avgustinik, the oxide content Ca, Mg, Fe, Na, K and attitude Al₂O₃/SiO₂ was taken into account. In order to obtain the densest packing, when calculating the grain composition, the natural dispersion of siliceous clays and the grain composition of previously prepared argillites were taken into account. The obtained theoretical calculations were tested in practice. Practical results showed that the 15% introduction of siliceous clay with the ceramic mass composition made it possible to obtain clinker tiles with improved physical and mechanical properties.

Abstract: Cement compositions based on slag Portland cement and fine dispersed slag component are considered. It has been established that the introduction of 1-3% fine slag obtained as a result of ultrafine grinding in a jet mill into the slag Portland cement composition provides an increase in the strength and structural characteristics of cement stone from the first day of hardening, which is important for slag cements. To ensure the fine dispersed slag particles’ stabilization in the cement matrix, the cement compositions were sealed with water with the addition of a plasticizer on either sulfa-naphthalene formaldehyde or polycarboxylate substrates in an amount of 0.5% of the cement composite content. In the research course it was found that in the initial stages of hardening and grade age, the strength of the samples containing a fine dispersed slag component and a sulfa-naphthalene formaldehyde-based plasticizer increased by 20%. When the cement composition is mixed with water with a polycarboxylate-based plasticizer, an increase in strength in the initial period of hardening by 60% is noted, at the vintage age - by 30%. At the same time, the porosity of the samples based on slag Portland cement with the addition of fine dispersed slag and one of the plasticizers in the initial period was reduced by 16-21%, at the vintage age - by 33-35%.

Abstract: One of the effective ways to solve the environmental problems of the region at present is the waste disposal from Novocherkasskaya TPP, one of the largest sources of environmental pollution. The solution to this problem is associated with the integrated use of ash and slag mixtures components in the effective building materials’ production. On the TPP waste basis, the authors obtained structural and heat-insulating concrete with enhanced physical, mechanical and operational characteristics.

Abstract: The article shows the prospects of using large-sized ceramic stones for modern housing construction. A review of the raw materials and technologies for their production is given. It is emphasized that the most promising technology for the large-sized ceramic stones’ production is a hard extrusion technology with the possibility of laying raw products on firing buggies and accelerated drying and firing modes. The characteristic of waste piles processing screenings in East Donbass, which are considered to be the by-products of coal mining, as the main raw material for the large-sized ceramic stones’ production is given. Their ceramic properties and results of the raw materials’ selection are given, including: screenings - 60-65%; siliceous clay - 20-30% coal sludge - 10-15%, on the basis of which it is possible to obtain the products with low cost and high strength for the load-bearing wall structures. The features of the ceramic material microstructure based on the obtained raw material mixtures with optimal porosity are noted. It is shown that the waste piles’ involvement in the process of ceramic stones production will make it possible to obtain products with a density of less than 800 kg/m³, less thermal conductivity 0,20 m·°С)/W and the brand strength M150 and above, with a minimum cost. This will create a serious competition for gas silicate products and achieve a level of ceramic stones’ use in the total volume of wall products for the housing construction of 80%, like in Western Europe.

Abstract: The obtaining carbonized material experimental studies’ results based on lime carbonate systems by 3D inkjet printing are presented. Some types of materials used as binders for inorganic binders have been studied. An effective method of hardening the model obtained in the 3D printing process is determined. The physical and mechanical characteristics of the prototypes hardened in the carbon dioxide medium or high concentration are determined. It was found that artificial carbonization of the samples obtained on various types of binders for 90 min contributes to the formation of a fairly strong structure of insoluble calcium carbonate, the hydrated lime carbonation product, and the carbonization degree depends on the type of binder and its mass fraction in the solution. The most effective types of binders were selected and the optimal content of the studied binders in the solution was determined.