On the selection criteria for cement mixtures for 3D printers with dry feed systems

The rheological properties of concrete mixtures are crucial for additive construction technologies. Methods for ensuring the required properties vary depending on the method of material preparation and feeding to the extruder: ready-to-use or dry concrete mix may be used. This paper examines the principles of regulating the initial shear stress, viscosity, and thixotropic index when using dry mixes for printing. The relative elongation of the mixture is proposed as a criterion for evaluating 3D printing mixtures. This parameter is determined both by direct measurement and by the thixotropic index, determined using a rotational rheometer. Using the example of a study of the influence of various modifiers (bentonite clay powder, redispersible polymer powders, medium and low viscosity cellulose ethers, polypropylene fiber) on the rheological characteristics in relation to the technology of feeding the mixture by the dry method, the possibility of selecting optimal compositions according to the proposed criterion is shown.