KEY WORDS:

complex hardener of liquid glass, sodium hydroxide, Portland cement, sodium fluorosilicate, liquid glass, unsorted glass breakage

ABSTRACT:

The production of aerated concrete based on liquid glass is associated with the formation of the structure of strong interpore partitions in them. Due to the process of polymerization of silicic acid, it is possible to control the structure formation of interpore partitions when producing aerated concrete based on unsorted breakage of technical glass. In turn, this provides the formation of an increased initial strength of aerated concrete. This can be achieved by using different types of hardeners. The purpose of this work is to determine an effective complex of liquid glass hardeners when producing aerated concrete on its basis and unsorted breakage of technical glass. In this work, mixtures of solid sodium hydroxide NaOH, Portland cement and sodium fluorosilicate (Na2SiF6) were studied as hardeners. It is shown that the use of a complex of various hardeners allows the procedure of formation of the aerated concrete structure, providing not only the strength characteristics of aerated concrete, but also increasing their water resistance due to the binding of readily soluble compounds into hardly soluble ones.

For citation: Samchenko S.V., Zaitseva A.A. Complex hardener for liquid glass for producing gas concrete based on unsorted technical glass breakage // Technique and technology of silicates. 2021.Vol. 28. No2. Pp 34 – 38.

KEY WORDS:
clay, alkali, binder, thermal activation, zeolites

ABSTRACT:
The article presents the results of a study of the effect of NaOH concentration (5-14 M) on mechanical properties, phase formation and composition of hardening products of thermally activated clays with a reactive phase content of 48% at a SiO₂ / Al₂O₃ ratio of 1.62. It was found that the greatest strength indicators are achieved when mixing thermoactivated clays 8M NaOH. The maximum formation of zeolites is achieved when using 11 M NaOH. The results were obtained at Na₂O / SiO₂ and Na₂O / Al₂O₃ ratio of 0.6 and 0.93, respectively. The main reaction products in the studied systems are sodium aluminosilicate hydrogel N-A-S-H, zeolite A, faujasite, analcime. The composition of the hardening products and the properties of the obtained binders make it possible to recommend them for the production of filling mixtures as matrices for the immobilization of radioactive waste.

For citation: Rakhimova N.R. Study of the influence of the concentration of an alkaline activator on the composition and properties of thermally activated clay by alkalis with an average content of clay minerals // Technique and technology of silicates. 2021.Vol. 28. No2. Pp 38 – 42.

KEY WORDS:
heat release, hydration, hardening, cement, capillary pores, strength, wetting, dispersing, protonation, structure, cement stone, calorimetry, silica fume, superplasticizer.

ABSTRACT:
In this work, kinetics, heat release in the cement - water system, in the presence of microsilicon and superplasticizer, were studied using the methods of differential microcalorometry. It is shown that during the hydration and hardening of cement, there is an alternation of heat generation processes, induction periods, crystallization processes with their alternating activation and decay at different times of structure formation. It was found that the addition of microsilica and a superplasticizer to the cement - water system leads to an acceleration of the hydration process and a more intensive formation of low-basic calcium hydrosilicates CSH (I). As a consequence, the strength of the hardening structures is increased and other performance characteristics of the cement stone are improved.

For citation: Lotov V.A., Sarkisov Yu.S., Gorlenko N.P., Zubkova O.A. Thermokinetic studies in the "cement-microsilica-superplasticizer-water" system // Technique and technology of silicates. 2021.Vol. 28. No2. Pp 42 – 49.

KEY WORDS:
repair composition, Portland cement, microcrystalline cellulose, nanocrystalline cellulose, strength, cement stone

ABSTRACT:
The influence of the concentration of micro- and nanocrystalline cellulose on the strength characteristics of cement stone and repair composition based on Portland cement is considered. The optimal content of microcrystalline cellulose and the optimal concentration of nanocrystalline cellulose for obtaining repair compositions with increased strength in compression and bending have been revealed. It is shown that when the content of microcrystalline cellulose is up to 1.4 wt. % the strength in compression and bending of repair compounds increases, respectively, by 23.2 and 21.9%. It was found that the use of an aqueous suspension of nanocrystalline cellulose as a modifier of repair compositions increases their strength in compression and bending by 35.5 and 20.3%, respectively. A possible mechanism for increasing the strength of building composites modified with nanocrystalline cellulose is proposed.

For citation: Ushkov V.A., Kozlova I.V., Surov O.V., Nalbandyan G.V. Influence of micro- and nanocrystalline cellulose on the strength characteristics of the repair composition // Technique and technology of silicates. 2021.Vol. 28. No2. Pp 49 – 53.

KEY WORDS:
hydrated cement suspension, structure formation of the cement system, nanosized particles of hydrated phases, modifier.

ABSTRACT:
The efficiency of using a pre-hydrated cement suspension as a modifier of cement paste is shown. Such cement slurries are formed when washing concrete mixing devices. It has been proven that when using a pre-hydrated cement slurry, it is possible to regulate the rheological characteristics, the kinetics of setting and hardening of the modified cement stone.
The modification of the structure of the cement stone was carried out using a synthesized modifier additive consisting of pre-hydrated cement grains and nanosized particles of hydrated phases and a plasticizer. The additive was synthesized by preliminary hydration in an aqueous medium for 6 hours and subsequent hydrodynamic treatment of this suspension, followed by the introduction of the C-3 plasticizer. The resulting suspension was used as mixing water for the cement system.
The results of experimental studies of the influence of a pre-hydrated cement suspension on the processes of early structure formation of a cement system are considered. It was found that an additive consisting of pre-hydrated cement grains and nanosized particles of hydrated phases and a plasticizer leads to an increase in normal density by 13%, accelerates the setting processes, provides a 10% increase in strength in the first day of hardening compared to the unmodified system. The optimal dosage of pre-hydrated cement suspension is 10% of the cement mass. The achieved results are explained by the effects of structure formation of the cement system and are associated with the manifestation of hydrated phases by nanosized particles as nuclei of structure formation or as a substrate for crystallization of neoplasms.

For citation: Samchenko S.V., Egorov E.S. Controlling the properties of cement paste when it is modified with a pre-hydrated cement suspension // Technique and technology of silicates. 2021.Vol. 28. No2. Pp 54 – 58.

KEY WORDS:
intrinsic self-sensing concrete, red mud, electrical resistivity, strength

ABSTRACT:
The article discusses the possibility of using "red" sludge - waste of alumina production as an additive to create ISS-concrete (intrinsic self-sensing concrete). It has been established that the introduction of red mud into the composition of the cement matrix reduces the specific electrical resistance of the cement stone by three times. Also, tests have established an increase in the strength of concrete with the addition of red mud, especially in the early stages of hardening.

For citation: Niyazbekova R.K., Konkanov M.D., Krivoborodov Yu.R. Investigation of the electrical conductive properties of cement compositions with the addition of "red" mud // Technique and technology of silicates. 2021.Vol. 28. No2. Pp 58 – 61.