Materials Science Forum Vol. 968

Abstract: There are shown studies on development of the alkali-activated slag cements and concretes using Chinese raw materials. Such cements and concretes are able to provide high performance characteristics of materials and constructions under exposure of sea climate. The tests had been done for compliance with the requirements set in the national standards of P.R.China and were determined characteristics of strength, wet conditions shrinkage, freeze-thaw resistance, corrosion and weather resistance, biodegradability, water permeability, bond strength between concrete and reinforcement. The obtained positive results of tests allowed to recommend them for a pilot-scale production of the developed materials in sea construction for protection of the sea coastal line in the P.R.China.

Abstract: The peculiarity of alkali-activated slag cements (further, AASC’s) is increased proper deformations, which can cause increased cracking and reduced durability of structure. The paper is devoted to manage AASC’s proper deformations. The main task was to determine the composition of complex additives (further, CA’s) in system «ordinary portland cement (further, OPC) clinker - mineral compound of different anionic type - surfactant» in presence of sodium metasilicate (further, MS) to affect on hydrated AASC performance while ensuring effective structure of artificial stone by criterion of shrinkage deformations. Comparative analysis of hydrated cement systems "OPC clinker - MS", "OPC clinker - mineral compound - MS" and "OPC clinker - mineral compound - MS - surfactant" showed that the greatest effect on reduction of proper deformations occurs when the mineral compounds relate to electrolytes, i.e. Na₂SO₄ and NaNO₃. Hydrated system is characterized by expansion (+0,062 mm/m) in presence of Na₂SO₄. Almost no shrinkage is supplied by application of NaNO₃ (-0,062 mm/m). The obtained CA’s were tested in AASC. CA in the system “OPC clinker - NaNO₃ - surfactant” provides the initial setting 43 min, the end - 65 min with accelerated strength. Investigated AASC can be classified as non-shrinking cement. This phenomena is ensured by increasing density, homogeneity and monolithicity of hydrosilicate formations, as well as due to formation of hydroaluminosilicate structures with different morphology by inclusion of nitrate anions.

Abstract: The article is devoted to ranking of quality criteria for multiparameter, multicriteria production technology of lightweight concrete depending on their significancy using fractal formalism. The proposed approach allows to determine the operation area of stability of the physicomechanical properties of expanded clay concrete with preset technology parameters depending on the size of their self-similarity area and to control the technological process relative to the determine parameter - watertightness. For concrete thin-walled hydraulic structures watertightness is one of the main indicators of quality, ensuring the durability of structures. In the experiment conducted on 15 points optimal plan, 3 factors of the composition varied: sulfate-resistant portland cement, silica fume, water reducing admixture. Possibility of ranking the indicators of W/C and physicomechanical properties of expanded clay concrete depending on the variation of concrete mixture components is shown. Stability of physical and mechanical properties of expanded clay concrete is necessary to ensure its durability and accordance with design requirements. Expanded clay concrete similar to those described in this article can be used in reinforced concrete shipbuilding to reduce weight of structures.

Abstract: The purpose of the research findings, given in article, is aimed to determine the rational compounds of concrete with an average cubic compressive strength less than 20 MPa with minimum required expenditures of cement. To reach the goal, mathematical planning of the experiment was used with variability of cement consumption from 90 to 190 kg / m³ in the compositions of the concrete mixture, and for the fine-grained filler from tails of processed ores, the consumption was like at 100 to 400 kg / m³. The result of processing experiments has shown us the dependences of the change in strength and coefficient of efficiency of the use of cement of the factors involved. Optimized values increase most intensively with minimum cement consumption and a change in the consumption of fine filler within the limits of the study. The highest coefficient of efficiency of use of cement is expressed by the ratio of the achieved strength per unit mass of used cement in the concrete mix and it was obtained at a cement consumption of 90 kg / m³ and a filler of 400 kg / m³. Using the obtained dependences of optimized values on the factors under study, the composition of concrete may be predicted with a strength up to 20 MPa with the required amount of filler.

Abstract: Pure calcium carbonate, chalk, and coal wastes are taken as starting materials. The Gibbs energy of calcium carbonate decarbonization reactions is calculated. By the method of thermodynamic analysis, the effect of carbon and its gasification products on the calcium carbonate decarbonization process is investigated. The intensifying effect of organic matter during heat treatment of calcium carbonate is shown. In addition to carbon, the decarbonization reactions are influenced by gases evolved as a result of the gasification of the organic part of the coal waste. It is theoretically proven that the organic component of coal waste contributes to lowering the temperature of the onset and end of the decomposition of calcium carbonate. To confirm the theoretical background, experimental studies of the behavior of mixtures during heating have been carried out. The effect of organic matter on decarbonization of pure calcium carbonate and chalk has been studied. Thermograms have shown that less caloric energy is required for the decarbonization of chalk than for the decarbonization of pure CaCO3. Organic transformations occur in the material layer, which contributes to intensive heat transfer. The products of thermochemical transformations of the organic mass increase the efficiency of the process of decarbonization of calcium carbonate using the waste of coal enrichment in the composition of the raw mix. The organic component of the waste not only reduces the amount of heat energy expended on the endothermic process of calcination, its presence in the raw material mix reduces the temperature of the process of calcination as pure calcium carbonate and chalk.

Abstract: Using nanotechnological techniques of complex activation, the compositions and manufacturing technology of building composites on a silicate matrix of thermo-moisture hardening of reduced energy intensity have been developed.

Abstract: Theoretical and experimental investigations of the influence of concrete moisture, its age, holding conditions after its thermal moisture treatment and other factors on the specific electric resistance of the concrete of a C32/40 grade used for reinforced concrete sleepers have been carried out. The obtained research data allowed us to specify holding modes and the duration of them and these enable the generation of objective information on the specific electric resistance of the concrete used for the sleepers during their operation.

Abstract: Results of experimental researches about affectivity of firebiopotection products made from cane. Due to the unique properties of the cane, such as small volume weight, low thermal conductivity, rather high atmospheric resistance, high chemical resistance, the possibility of manufacturing parts at the site, efficiency, etc., cane products, despite the high pace of new technologies, are widely used in construction. Using cane in construction has a significant number of advantages, but needs protection from fire, from it produce a variety of products, equip the buildings. The unresolved issue of fire protection of products from such materials reduces the possibility of their use in construction. The experimental research on the determination of the fire-safety properties of the cane set the ignition of the raw sample, while for fire-proof - the process of ignition and propagation of the flame did not occur. Especially inhibition of the process of ignition and propagation of cane fire treated with a covering impregnation solution, which consist of fire retardants under the influence of temperature with the absorption of heat and the release of non-combustible gases (nitrogen, carbon dioxide), change in the direction of the expansion in the direction of formation of non-combustible gases and heavy-duty coke residue, reducing the combustion of the material and, accordingly, the index of flammability. This indicates the possibility of directed control of the processes of transfer of high temperature to organic material by using special covering compositions for cane products.

Abstract: The paper presents the development of optimum structures and the production of polymeric coatings technology which can absorb aggressive substances. The studies of coatings penetrating into the film are presented due to the organization of their capillary-cellular structure by introducing special fillers. A new approach to solve the problem of protecting the environment, people, buildings and structures from the effects of aggressive substances has been proposed. The essence of the method consists in the preventive deposition on the surfaces of construction objects of porous coatings that can irreversibly absorb aggressive substances. Based on theoretical and experimental studies, porous coatings have been developed that are capable of accumulating in their volume aggressive substances, as well as certain principles of providing the coating with the necessary capillary-porous structure. The mechanism of creating a capillary-cellular structure of a polymer coating based on nitrocellulose are substantiated.