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KEY WORDS:
cement, additive, photocatalysis, titanium oxide, bismuth oxide
ABSTRACT:
Modification of traditional cement building materials with various additives allows to provide them with unique functional characteristics. Photocatalytic cement materials have a set of properties that, such as high mechanical properties and the ability to self-cleaning of its surface due to the photocatalysis - a process that occurs in the structure of the material under the influence of light. It is possible to obtain photocatalytic cement material by modifying it with special additives. The most known photocatalytic additive is titanium dioxide of anatase modification. However, titanium dioxide demonstrates its photocatalytic activity only under the influence of ultraviolet radiation. It is known that a number of compounds based on the TiO2-Bi2O3 system show photocatalytic activity in the visible range of the spectrum. Consequently, the introduction of such compounds as an additive into the cement composite can improve its ability to self-cleaning. In addition, the photocatalytic activity of the additive is significantly influenced by its dispersion, which in turn directly depends on the method of synthesis. Thus, in this research, methods for obtaining an additive based on the TiO2-Bi2O3 system, the dependence of the dispersion and composition on the synthesis method, as well as the photocatalytic activity of cement stone samples modified with the additive were investigated.FOR CITATION: Kozlova I.V., Zemskova O.V., Samchenko S.V., Dudareva M.O. Methods of synthesis of a photoctalytic additive for cement systems. // Technique and technology of silicates. – 2023. Vol. – 30, No. 3 – Pp. 206-216.
ABSTRACT:
The fine particles of cement and fillers occupy the largest part of the total specific surface area and have the strongest influence on the total water content of the concrete mixture. The most appropriate is the use of materials with the lowest water demand, the correct determination of which for self-compacting concrete is very important to cover all particles with a layer of water of a certain thickness. Therefore, the study of the water demand of fine materials used in self-compacting concrete is an urgent task. The paper deals with the properties of the materials used in self-compacting concrete such as water demand, which is determined using a linear regression equation with a water demand coefficient Kwd and a deformation coefficient Kd, which represents the slope of the linear function or the degree of sensitivity to water release. The water demand values of Portland cement CEM 0 42.5N, fine ground granulated blast furnace slag and filer from recycled concrete were determined.
FOR CITATION: Larsen O.A., Samchenko S.V., Stenechkina K.S., Alpackiy D.G. The effect of fine materials on the self-compaction of concrete mix // Technique and technology of silicates. – 2023. Vol. – 30, No3. – Pp. 217 – 229.
KEY WORDS:
polymineral binding composition, calcium sulfoalumoferrites, strength, expansion.
ABSTRACT:
One of the directions of development of cement science is dictated by the need to develop binders with special properties, which are not provided by the use of cements for general construction purposes. Cements of aluminate and sulfoaluminate hardening, which can compete with special structural materials in terms of rate of strength growth and ultimate strength, have been most extensively studied and are now quite widespread. Using iron-containing materials (substandard bauxite, non-ferrous metallurgy slag) it is possible to obtain sulfoaluminoferritic clinker and cements based on it, which have high strength and corrosion resistance. The processes of structure formation of polymineral binding compositions based on alite (C3S), belite (C2S) and calcium sulfoalumoferrites of different composition (CAFC) minerals have been studied. The strength and expansion of polymineral binder compositions containing 30 to 70 wt.% calcium sulfoalumoferrites of different compositions have been determined. It is shown that cements made of calcium sulfoalumoferrites in combination with calcium silicates have high strengths. The compositions containing 65 % calcium silicates and 30 % calcium sulfoalumoferrites have the highest strength values in the vintage age, and their strength increases with the increase of A/F ratio in CAFC. It was shown that binder compositions containing 70 % SAFC have lower strength, but they have high values of linear expansion and self-stiffening. The obtained data formed the basis for the development of compositions of sulfoaluminoferritic clinkers.ABSTRACT
The influence of highly dispersed powder AEROXIDE TiO2 P25 with specific surface area equal to 50 m2/g, in the composition of white Portland cement on the change of its characteristics has been considered. The studies were carried out on two types of white cements differing in mineralogical composition. It was found that titanium dioxide affects such cement dough parameters as normal density, setting time and water separation. It is shown that normal density increases by 1.6-4.5 %, while setting time decreases by 6-15 minutes and water release decreases by 4-10 %. Determination of hydration activity of binder compositions by means of heat release showed that the thermal effect of adsorption stage increases by 15-20 %, the induction period of reaction flow is reduced by 30-40 minutes on average, and the flow of the main stage of cement hydration is intensified. Introduction of titanium dioxide in the composition of white Portland cement in the amount of 1 and 5 % TiO2 leads to a decrease in the strength parameters of cement stone in the initial terms by 5 and 18 MPa, respectively. In late terms (28 days) of hardening the strength of samples with 1 % TiO2 becomes comparable with control samples, and with 5 % - significantly lower than control (by 17-28 MPa).KEY WORDS:
ash and slag mixture, carbide sludge, silicate products, regression analysis
ABSTRACT
In recent years, in the Irkutsk region, the issue of disposal of accumulated waste at the site of Usolyekhimprom LLC has been quite acute, since the city of Usolye-Sibirskoye has been given the status of a priority development area, where it is planned to locate the Federal Center of Chemistry, a structural division of the State Corporation Rosatom, whose task is development and implementation of high technologies of various directions. Among the most large-scale wastes that hinder the development of the territory are the ash and slag mixtures of TEС-11, accumulated over the years of operation of the Usolskaya TEС and a by-product from the production of acetylene - lime-containing waste (carbide sludge), the volume of dumps of which today has reached 9 million tons. X-ray diffraction analysis showed that carbide sludge consists of 70 % Ca(OH)2, and the ash and slag mixture is 50 % represented by aluminosilicate glass and minerals such as quartz, mullite and sillimanite. Based on this chemical and mineralogical composition, the goal of our work was to assess the effectiveness of these wastes for producing autoclaved silicate products. Using the method of mathematical experimental planning, the dependence of the compressive strength of lime-ash stone on such technological factors as the specific surface of the raw material mixture, water content and isothermal holding time was obtained. The level of strength values obtained (up to 15.6 MPa) allows us to recommend the developed compositions of lime-ash mixtures for the wide production of autoclaved silicate building products.KEY WORDS:
cement composition, fine perlite, perlite suspension, injection solution, plasticizer, strength, relative viscosity, sedimentation
ABSTRACT
The work examined cement compositions prepared by mixing cement with a stabilized suspension of fine perlite. This made it possible to improve the physical, mechanical, and structural characteristics of cement stone. On the first day of hardening, the strength of the modified samples increased by 64%, at brand age - by 36.1%, porosity decreased by 14.2 and 15.8%, respectively.FOR CITATION: Krivoborodov Y.R., Kozlova I.V., Zemskova O.V., Borisenkov N.S. Development of cement compositions with fine perlite for injection fixing of soils// Technique and technology of silicates. – 2023. Vol. 30, No3. – Pp. 272 – 280.
KEY WORDS:
disintegrator, Portland cement, particle size distribution, specific surface area, bulk density, hollowness, degree of polydispersity, number of particle contacts, agglomeration
ABSTRACT
The purpose of the work is to evaluate the effectiveness of activation of Portland cement in a disintegrator at different modes of activation It is shown that this method of cement activation changes its particle size distribution and specific surface area. The increase in specific surface area for each subsequent activation of cement increases by 12-16% to the previous value. This is accompanied by a decrease in particle size and change in their shape, which leads to an increase in the number of contacts of cement particles with each subsequent passage of cement through the disintegrator by about 2 times. Cement activation at energy costs of 51 kJ/kg leads to distortion of the crystal lattice of minerals, increase of crystal defectivity and growth of their free energy. This causes the formation of large aggregates leading to the process of agglomeration of cement particles. It was found that during activation the bulk density decreases with increasing specific surface area. The lowest bulk density is found for cement activated at an energy of 17 kJ/kg. At higher energies (34 and 51 kJ/kg) the bulk density slightly increases due to the fact that small particles are placed in the interparticle voids of larger particles, while the void density sharply decreases. Cement autogestion, i.e. adhesion forces between particles due to electrostatic, adhesion and van der Waals interactions, leads to changes in the degree of cement polydispersity during its activation in a disintegrator. It is shown that at the first pass through the disintegrator the degree of polydispersity of cement sharply increases, and then sharply decreases due to the increasing proportion of small fractions.FOR CITATION: Samchenko S.V., Osmanov A.B., Abramov M.A. Evaluation of Portland cement activation efficiency in a disintegrator // Technique and technology of silicates. – 2023. Vol. 30, No4. – Pp. 281 – 291.