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.

Due to its novelty, futuristic appearance of created forms, a vivid contrast with a conventional image of a construction site, construction 3D printing attracts attention of a wide audience. Specialists see it as affording significant possibilities for saving all kinds of resources, reducing construction time, giving possibility to implement progressive design solutions, but they also see serious problems, such as: an immature general concept of development of additive technologies, a limited range and high cost of consumables, lack of methods for development of new compositions and lack of experience in application of such methods as a result. The paper analyzes links between the process factors and properties of molding components; principles of their practical implementation are proposed. Special attention is given to the issues in assessment of construction printability of newly-developed compositions.

Based on the knowledge that exists today, it is generally accepted that there are basic parameters and characteristics to obtain effective mixtures for their use in 3D printing. Rheological behavior and setting time (initial and final) are those characteristics that determine workability, as well as the speed and nature of hardening of the molded pastes and, as a result, the final framework and the integrity of the resulted structure. Among the promising options for 3D printing, the literature often contains information on alkali-activated binders. In this work, an alkali-activated binding system based on electrometallurgical slag, as well as citrogypsum, a waste of the industrial production of citric acid, was studied. Some rheological characteristics of experimental binders were considered: the nature of the mixture flow under the action of torsional loads and their initial and final setting times. It was found that the joined use of both components in the experimental system “slag - water”: an alkaline activator and citrogypsum, promotes the transition of the character of the system from thixotropic to mixed: dilatant-thixotropic (for the Na2SiO3 activator) and dilatant (for the NaOH activator). It was found that the addition of alkaline activators and citrogypsum to the binding system separately in both cases helps to reduce the initial and final setting times from 18 and 22 hours to 1 hour and 1.5 hours. Also, experimental results have shown that the jointed action of both components: an alkaline activator and cytogypsum, has a synergistic effect on the setting time.

No abstract

when hardening the binder system and it transforms into a consolidated conglomerate, the efficiency of the for-mation of the structural framework and the main operational characteristics of the final product dramatically de-pend on the thermal and humidity conditions of the environment medium, where the binder or raw material is con-solidated. In this study, various conditions of hardening of binders with alkaline activation of various composi-tions 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°C, 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