Materials Science Forum Vol. 1011

Abstract: The results of studies on the foam concrete and fiber concrete development based on volcanic tuff dusting waste are presented. The foam concrete compositions that can significantly reduce the Portland cement consumption and at the same time increase its strength properties are proposed. To study the dispersed reinforcement parameters’ effect on the properties of fiber-reinforced concrete, an experiment with a second-order composite rotatable plan such as a regular hexagon was conducted. The use of fosta nylon fibers in foam concrete increases their strength properties and positively affects the structure. Dispersed fibers not only reinforce the matrix, but also significantly change its structure indicators, in particular, porosity indicators (uniformity of pore diameter distribution, average pore size), which in turn affects the strength characteristics of the material.

Abstract: The studies’ results to determine the gypsum, ash and Portland cement components proportions, which would ensure a decrease in the specific binder consumption, as well as the ash grain composition’s effect on the properties of the gypsum cement pozzolan composite, are presented. It was revealed that the use of volcanic ash together with Portland cement in gypsum concrete composites allows reducing gypsum consumption by up to 50% without a significant decrease in strength characteristics. At the same time, the developed gypsum concrete composites have increased water resistance. The influence of the ash particle size distribution on the strength properties of the composite is ambiguous; in the compositions with a high ash content it is advisable to use larger fractions, and with a content of less than 50% ash in the composite, - the small fractions. To study the parameters’ effect of the dispersed reinforcement with basalt fibers on the properties of a gypsum-cement composite, an experiment with such a second-order composite rotatable plan as regular hexagon was conducted. It was found that the maximum values ​​of optimization parameters are observed in the central area of ​​the plan with and . The compressive strength of a fiber gypsum cement pozzolan composite increases by 1.15-1.18 times, when bending, by 1.56-1.72 times with respect to the strength of the initial matrix.

Abstract: Improving the hydration hardening building materials’ operational properties is possible due to the stable macro-, micro-and nanostructures’ creation by the cementing material crystalline aggregate directed modification, which can be achieved through the use of various additives acting as crystallization centers. In the course of the studies, the synthesized modifier effect nature represented by the system was revealed CaO-SiO₂-H₂O (CSH) on the properties of non-autoclave silicate materials using aluminosilicate binder of various compositions. It has been established that the use of an aluminosilicate binder together with the addition of a CSH modifier increases the presence of a crystalline phase at all stages of hardening, as well as intensifies the synthesis of low-basic calcium hydro silicates with a higher crystallization degree in the system CaO-SiO₂(Al₂O₃)-H₂O represented by lime and clay rocks. This contributes to the micro-reinforced crystalline framework formation of the neoplasms with increased strength. Due to this, the pore space decreases and the amount of synthesized crystalline substance increases, which helps to increase the water resistance of the samples in all compositions. The samples using an aluminosilicate binder and the addition of a CSH modifier achieve maximum strength with a CaO content of not more than 10 wt. % The optimal CSH modifier addition is up to 1.5 wt. %, with 7 wt. %, CaO content in a mixture increase in strength is up to 6%.

Abstract: The study results of the calcareous composites made with the use of activated mixing water are presented. Quicklime and slaked lime are used as lime binders. The mixing water was activated by the electric current and magnetic field in various modes. The effect of water activation on the physical and mechanical properties of slaked and quicklime composites and the resistance to the effects of the biological environment are studied. The water for mixing electromagnetic treatment effectiveness analysis is presented. The increase in the density of materials based on lime, trapped in activated water using ultrasound tests is proven. It was found that the mixing water activation affects the structure formation of composites and, under certain activation conditions, leads to an increase in such physical and mechanical parameters as strength and hardness. The positive effect of the mixing water activation on the lime-based materials’ resistance to microbial growth has been established, and the decrease in the growth of composites based on quicklime and slaked lime has been proved.

Abstract: The article is devoted to the study of the light concrete shrinkage deformations’ development patterns on porous aggregates of the volcanic tuff Kamensky deposit in Kabardino-Balkaria, prepared on quartz and tuff sands, using an expanding additive of sulfo-aluminate type in the amount of 12.5% Portland cement mass, the composition and amount of which was determined by the DSTU method.

Abstract: Recently, the frame composite materials have been developed greatly at the production introduction level. The manufacturing technology of these materials is carried out in two stages: first, large aggregates are glued into the frame, and second, the porous frame voids are impregnated with the matrix component. In this article, we studied the various aggregates’ effect on the polymer concrete frame structures properties using epoxy binders. The materials based on the quenched cullet, brickbats, granite and limestone crushed stone, and the polymer granules were considered as large aggregates. The studied properties were the strength and elastic modulus. Quantitative dependences of compressive and bending strength, elastic modulus of frame composites on the aggregate type and other prescription factors are obtained. Using the methods of mathematical experimental planning, the optimal particle size distribution for the composites with grains from quenched cullet was selected. Particular attention should be paid to the possibility of using industrial wastes in polymer concrete compositions: polymer granules, quenched cullet and brickbats. Used glass makes up about 10% of the household waste. Its reuse is usually associated with high capital costs allocated for sorting glass by color, removing stones and other impurities. Glass grinding allows to get a fine-grained filler and aggregate. Strength and deformation characteristics of the matrix compositions, frameworks and composites as a whole are determined.

Abstract: The studies to establish the species composition of micro-mycetes inhabiting the surface of cement composites after aging in sea water have been carried out. Cement stone made on the basis of Portland cement clinker, a mineral additive and a fungicidal preparation was considered as the studied material. To determine the materials’ fouling by microorganisms, their species composition, imprints and sampling methods were used. A change in the species composition of mycobiota isolated from the cement composites’ surface modified with sodium sulfate and sodium fluoride depending on the amount of active filler, gypsum, and biocidal additives was experimentally revealed. The effectiveness of using the biocidal cement composites with an active mineral additive has been confirmed. It was found that the composites on the developed compositions showed higher resistance compared to the materials on ordinary cement. The compositions modified with biocidal additives showed a fungicidal effect.

Abstract: Energy saving in buildings is largely determined by the energy efficiency of the external building envelopes. The latter, as a rule, are the multilayer and incorporate structural and heat-insulating layers. The presence of individual hygroscopic salts and their mixtures in building materials changes their physical and chemical properties. Due to the increase in the sorption properties of building materials and changes in the inter-pore substance composition, humidity increases and the heat-protective properties decrease. This paper presents the results of the experimental and theoretical studies on the salts’ effect assessment on the change in moisture content and thermal conductivity of building materials due to the salt solutions and crystals’ presence in the pore space. To study the saline building materials’ thermal conductivity, the mathematical modeling methods using the theory of flow and bringing the materials’ structure to a unit cell are used. It is shown that the change in thermal conductivity occurs due to the crystalline salt precipitation from the solutions in the material’s pores, to the changes in their initial chemical properties, to the changes in the properties of the vapor-air mixture above the salt solutions due to diffusion. The results obtained make it possible to establish the hygroscopic salts’ influence significance in solid and liquid phases on the building materials’ thermal conductivity. A scheme for determining the thermal conductivity of building materials is proposed, taking into account salt effects, including the determination of: the components’ volume concentrations; sequentially the thermal conductivity of the material’s shell; salt crystals, a solid phase consisting of the material’s shell and crystalline salt, a binary and multicomponent saline solution, the pore space and the pore substance inside. The general formula for determining the thermal conductivity of a saline building material is given.