Additive technologies are widely used in various industries. However, nowadays, the large-scale implementation of these technologies in the construction industry is difficult, due to a lot of open practical and scientific questions in terms of both building mixtures and 3D printing equipment. When performing studies focused on the development of cost-effective mixtures based on readily available raw materials for building extrusion 3D printing, it was found that the final result was determined by the rheology of the building mixture, the speed of the screw, and other factors. The article studied the combined effect on the extrusion of the building mixture and the parameters of the printed track of such factors as the thickness of the layer, the linear printhead traversed velocity of the forming device, and the speed of rotation of the screw. We aimed to establish relationships between the above factors, providing an increase in the stability of the printing process and the quality of the resulting structure. To carry out the research, an experimental program and original methods were developed, involving printing in different regimes using a laboratory construction 3D printer. Based on the regression analysis of the data obtained, it was found that the process of 3D printing by extrusion methods cannot be described by a linear function. It was found that a change in the linear speed of the nozzle movement can increase the yield of the mixture, and also lead to track stretching and the degradation of some parameters. The boundary value, in this case, is the layer thickness of 0.77–0.8 of the nozzle width. The response of the system to changes in the linear printhead traversed velocity and the frequency of rotation of the screw occurs in different ways. A change in the linear printhead traversed velocity at the optimal height of the layer has a slight effect on its width. Reducing the speed of rotation of the screw leads to a decrease in the overall dynamics of the mixture flow and an increase in its viscosity due to its thixotropic nature. When the previous speed of rotation of the mixture is restored, the dynamics of the flow are restored with a noticeable delay. In general, this is recommended to ensure the highest dynamics of the printing process. For the laboratory construction 3D printer and the building mixture used in the article, the regime with the following parameters was recommended: a linear printhead traversed velocity of 900 mm/min; an extruder frequency of 25 rpm; and a relative layer thickness of 0.8 (of the nozzle width). This regime provides the optimal ratio of performance/quality and the stability of track parameters.

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Introduction. In recent years, there has been an active development of 3D additive technologies. This trend could not but affect the construction industry. However, printing using plastics and other organic compounds differs significantly in its technological features from printing with building compounds. Concrete and mortars used in layer-by-layer printing must have a number of technological properties, such as sufficient viscosity for extrusion by an extruder, low mobility to maintain geometry after laying, high setting speed and strength after hardening. Currently, there are a number of compositions that meet these requirements, however, they, as a rule, are not distinguished by high strength and require a wide raw material base, which may not be available in field printing conditions. As a result, it is necessary to expand the range of building materials for 3D printing, suitable for the above criteria, as well as satisfying economic indicators.Materials and methods. Research has been carried out using physical and mechanical tests, X-ray phase analysis and electron microscopy on the effect of finely ground mineral additives on the microstructure and hardening processes of composite binders with various dosages of functional additives.Results. The results of studies on the production of composite binders for 3D additive technologies using Portland cement and man-made waste - waste of wet magnetic separation of the Stary Oskol electrometallurgical plant, modified with additives accelerators (Technonikol Master) and plasticizers (Polyplast PK-R) using mathematical planning and construction of mathematical models for composite binders with different hardening times are pesented.Conclusion. The efficiency of using the obtained composite binder has been proven, the use of which provides an increase in rheological properties, and also makes it possible to save expensive portland cement.