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Kozhukhova M.I.

Candidate of Engineering Sciences (Ph.D.), Research Officer, University of Wisconsin-Milwaukee, the USA

THEORETICAL ASPECTS OF DEVELOPMENT OF COMPOSITE NANOSTRUCTURED GYPSUM BINDER CHARACTERIZED BY INCREASED HEAT RESISTANCE

https://doi.org/10.34031/2618-7183-2019-2-4-5-13
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 5-13 p.
Abstract
There are a lot of different types of binders for construction purpose, a strong interest is focused on free-of-cement binders of new generation, which are characterized by unique and/or improved performance proper-ties. Among them there is composite nanostructured gypsum binder (CNGB) as a quite new binding system. In the framework of this study the hypothesis of synergetic effect in hardened binding system was proposed and approved. The hypothesis is realized when interaction of two binding systems with different structure formation mechanism such as followings: polymerization-polycondensation and hydration. A number of experiments were carried out and the results were obtained, which demonstrate a resistance of CNGB under high-temperature effect (up to 1000ºC) vs. ordinary gypsum binder. It was determined that a heat-resistance of CNGB is associated with joint crystallization of sulphate-based component (gypsum binder) and highly-reactive silica-based component (in nanostructured binder). Normally, nanostructuted binder is stable under high-temperature exposure. The indicator of synergetic effect is formation of new crystalline phase – hydroxyellestadite Ca5(SiO4)3(SO4)3(OH)2. This phase has unit cell size which is stable under temperature gradient. This characteristic allows saving structure framework in CNGB under high temperature.
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CHEMICAL REACTIVITY ASSESSMENT METHOD OF NANOSTRUCTURED LOW CALCIUM ALUMINOSILICATES

https://doi.org/10.34031/2618-7183-2019-2-3-5-11
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 5-11 p.
Abstract
Nowadays, the production of high-performance composites is a relevant objective in construction industry. Normally, geological and/or technological conditions of phase formation are responsible for chemical and structural characteristics of raw materials. In this regard, the use of a certain material dictates terms to opti-mizing production process, efficient use and, therefore, requires to develop a method for quality evaluation of raw materials. This approach allows a considerable time saving and raw materials sources, while the evaluation of final performance characteristics of designed materials is being done. The biggest interest in this area is focused on new types of developed and poorly-studied composite systems which results in a lack of capacity to design materials with known performance and, therefore, constrains the areas of application of construction composites
Among such composite systems there are zero cement alkali-aluminosilicate systems or geopolymers. For geopolymers production a wide range of different aluminosilicates with varied characteristics potentially can be used. And also, in each certain case, the quality evaluation methods for aluminosilicates should be different.
This study is focused on chemical reactivity assessment method of crystalline (mainly, nanocrystalline) low calcium aluminosilicates exposed to high-alkali media. The solubility degree in high-alkali media and compressive strength performance were evaluated in this study in order to define chemical reactivity of low calcium aluminosilicates. The compressive strength data demonstrated a positive correlation with the crystallinity degree of aluminosilicates.
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STRUCTURE FORMATION IN ALKALI ACTIVATED ALUMINOSILICATE BINDING SYSTEMS USING NATURAL RAW MATERIALS WITH DIFFERENT CRYSTALLINITY DEGREE

https://doi.org/10.34031/2618-7183-2018-1-4-38-43
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 38-43 p.
Abstract
The efficiency of traditional raw materials using as well as expanding of potential uses for non-conventional and alternative raw materials with different origin is the tasks exiting interest among material scientists and manufacture stuff. Investigation of the above is oriented on solution of such scientific problem as more deep understanding of structure and features of material. The results obtained also allow solution of some technological, technical and economical tasks.
Greatly, it is actual when using of new types of raw materials as well as when synthesis of new composites. Concerning the construction material science field, the classic problem is the looking for ways to study the reactivity of raw components under different conditions, its control and, generally, its increasing to produce higher performance materials.
Among the popular and widely-used construction materials are alkali-activated binders and relevant composites.
In this study the results of granulometric analysis of suspension based on alkali-activated aluminosilicate with different crystallinity degree are presented. It was found, when treatment of aluminosilicate grain by alkali activator leads to the grain solubilizing (but differently depending on crystallinity degree of aluminosilicate) and formation of alkali-aluminosilicate gel that reacts with unreacted part of the grain according to structure affinity principle. It was also determined the crystallinity degree of aluminosilicate component is inversely proportional to its solubility in highly-alkali environment. The model of structure formation for geopolymer system under alkali effect is offered.
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ANALYSIS OF THE FACTORS OF INCREASING THE STRENGTH OF THE NON-AUTOCLAVE AERATED CONCRETE

https://doi.org/10.34031/2618-7183-2018-1-1-59-68
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 59-68 p.
Abstract
Non-autoclaved aerated concrete is the only real alternative to gas silicate in the organization of its release on the basis of regional production of small and medium capacity. This will help improve the competitive environment in the building materials market and optimize the cost of construction. Of particular interest is the possibility of expanding the field of application of this material due to a significant increase in strength characteristics, while maintaining its average density in acceptable, in terms of thermal insulation properties, limits - not more than 1000 ... 1100 kg/m3. At a strength level of 10 MPa and above, in combination with dispersed reinforcement or the use of traditional non-metallic reinforcing elements, such aerated concrete can be used as a lightweight structural material for creating power elements of low-rise buildings, including in promising construction printing technologies; devices distributing the load belts; non-removable formwork; porous, stiffening, filling thin-walled tubular structures. The paper presents an assessment of the effectiveness of traditional ways to increase the strength of non-autoclaved aerated concrete. New solutions for the purposeful formation of the pore space structure are proposed and tested due to the creation and use of a gas generator with normalized gas evolution, which allows the creation of pores of a given volume. The key to the economic effectiveness of the proposed solutions is the transition from traditional portland cement to composite binders based on it. The substantiated choice of the amount and composition of the mineral additive makes it possible to optimize the properties of the binder under the particularity of the problem being solved, and to minimize the consumption of cement and chemical modifiers, increase the speed of durability and the final indices of non-autoclaved aerated concrete.
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