Structure and Properties of Fine-Grained Concrete Based on Gypsum-Cement-Pozzolan Dry Mortars for 3DCP

3D concrete printing (3DCP) is one of the most important priorities for the development of the construction industry around the world. Despite optimistic forecasts for the growth of additive construction technology in the long term, there are various risks that can influence the pace of this development, which are associated, first of all, with the need to develop the regulatory framework, train qualified personnel, create and improve equipment and materials for 3DCP – seal. There is a lot of research aimed at creating and developing the scientific basis for the design of concrete for construction 3D printing; compositions of dry mortars for additive manufacturing based on mineral binders, mainly cement, have been proposed; much less attention is paid to composites based on gypsum and mixed – gypsum-cement-pozzolan binders (GCPB). The purpose of this work is to study the structure and properties of fine-grained concrete for 3DCP based on gypsum-cement-pozzolan dry mortars. The molding of samples during experimental studies was carried out using the layer-by-layer extrusion method on a workshop construction 3D printer “AMT S-6044”. The rationality of using concrete with a ratio of GCPB:aggregate = 1:2 in the additive manufacturing technology with a sand fineness modulus of Mk 3 has been substantiated. A composition of gypsum-cement-pozzolanic concrete (GCPC) modified with a multifunctional complex additive has been developed, which allows increasing the compressive strength by 35.3%, water resistance – by 73% (up to 0.85) compared to the control unmodified composition. It has been established that modification of GCPB with the developed multifunctional complex additive leads to a decrease in the volume of open capillary pores by 20.5%, the volume of open non-capillary pores – by 66.7%, an increase in the volume of conditionally closed pores by 28.1%, and the microporosity index – from 0.22 to 0.89. The synergistic interaction of chemical additives in complex additive composition is confirmed by the results of studies performed to determine the electrokinetic potential on the surface of GCPB particles and the kinetics of heat release during its hydration.