Shurakov I.M.

Master of Arts (M.A.), Belgorod State Technological University named after V.G. Shukhov, Russia

EFFECT OF THE CURING CONDITIONS ON THE CHARACTERISTICS OF CITROGYPSUM-CONTAINING ALKALI-ACTIVATED BINDERS

https://doi.org/10.34031/2618-7183-2021-4-5-24-34
Abstract
When hardening the binder system and it transforms into a consolidated conglomerate, the efficiency of the formation of the structural framework and the main operational characteristics of the final product dramati-cally depend on the thermal and humidity conditions of the environment medium, where the binder or raw material is consolidated. In this study, various conditions of hardening of binders with alkaline activation of various compositions were studied. Based on the literature analysis, the following were chosen as the hardening conditions for the experimental alkali-activated systems: 1) - thermal drying, which was carried out in an oven at a temperature of 60°C for 24 hours; 2) hardening in ambient laboratory conditions, at a temperature of 23 ± 2°С, relative humidity - 33 ± 2%. An aqueous solution of alkali NaOH and salt Na2SiO3 were used as alkaline activators. The resulted data of the change in the average density showed that when using an alkaline activator, heat drying promotes the compaction of the hardened composite (typical for both types of the alkaline component) by 5 and 7 % for NaOH and Na2SiO3, respectively. The absence of alkaline activators in the experimental samples leads to decompaction of the structure after exposure to thermal drying and a decrease in the average density to 18%. The experimental results showed that thermal drying contributes to an increase in the strength parameters of experimental samples of an alkali-activated binder using Na2SiO3 to 110% (from 1.9 to 4 MPa). For the rest of the samples, a significant decrease in strength is observed (more than 2 times). A visual analysis of experimental samples of alkali-activated binders showed that the binders containing the addition of citrogypsum showed clear signs of efflorescence in the case of their hardening in ambient laboratory conditions. At the same time, for similar compositions from a series of samples hardened under thermal drying conditions, there is a complete absence of this phenomenon.
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OPTIMIZATION OF RECEPTURAL-TECHNOLOGICAL PARAMETERS OF MANUFACTURE OF CELLULAR CONCRETE MIXTURE

https://doi.org/10.34031/2618-7183-2018-1-2-30-36
Abstract
Aerated concrete at the moment is one of the perspective thermal insulation materials. However, the production of high-quality aerated concrete products is associated with a number of difficulties, primarily related to the features of the manufacturing technology and, in particular, to the formation of its structure during the period of gas evolution and the impact on this process of a large number of factors. The best conditions for the formation of cellular concrete are created when the maximum gas release and the optimum values of the plasticity-viscous characteristics of the aerated concrete mixture are found. Achieving optimal conditions is extremely difficult, which leads to a deterioration in the physico-mechanical characteristics of the final products. One of the ways to solve this problem is to increase the amount of mixing water, however, along with a positive effect (reducing the viscosity of the system), this leads to a decrease in the gas-holding capacity of the mixture. In this connection, the possibility of increasing the production efficiency of the cellular concrete mixture by optimizing the recipe-technological parameters was considered. With the help of the method of mathematical planning, a three-factor experiment was carried out, as the factors of variation were: the duration of the preliminary aging of the mixture, the dosage of the blowing agent and the water-hard ratio, the output parameters were the compressive strength and the average density of the final products. The obtained results made it possible to reveal the regularities of the change in the output parameters from the variable factors and to establish that the preliminary aging of the mixture before the introduction of the gassing agent positively affects the structure and, as a consequence, the physico-mechanical characteristics of the final products.
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