Improving the Performances of a Mortar for 3D Printing by Mineral Modifiers

Erection of buildings using 3D printing has great potential. However, its mass use for high-rise buildings is hampered by the lack of cement mortars with the required technical characteristics, the most important of which is high plastic strength (in the first minutes after pouring). The significance of the work (novelty) lies in the creation of a composite binder using a mineral modifier obtained by joint grinding up to 500 m(2)/kg of bentonite clay, chalk, and sand. A comprehensive study of the developed mortars was carried out from the standpoint of the necessary characteristics for volumetric concreting of high-rise thin-walled buildings. A composite binder for high-strength composites (compressive strength up to 70 MPa) has been obtained, which can provide effective mortars for 3D-additive high-rise construction technologies. The influence of the genetic characteristics of the modifier components on the properties of the composite binder has been established. The hydration process in this system of hardening concrete of the optimal composition proceeds more intensively due to the significantly larger specific surface of the mineral modifier components, which act as an active additive and activators of the crystallization of new growths. It has been proven that the features of mortars of high-strength fine-grained composites for 3D-additive technologies of high-rise buildings must meet special properties, such the rheotechnological index and the bearing capacity of the freshly formed layer (plastic strength or dimensional stability). Compared with a conventional mortar, the plastic strength of the developed one increases much faster (in 15 min, it is 762.2 kPa, in contrast to 133.0 kPa for the control composition). Thus, the strength remains sufficient for 3D printing of high-rise buildings and structures.