Compatibility of viscosity modifiers and hydrophobic agents in ensuring concrete adhesion for 3D printing

Introduction. In 3D construction printing, where large volumes of concrete are involved, it is necessary to allow for construction breaks and to divide the structure into sections; at the same time, the concrete mix must have time to develop its load-bearing capacity as the vertical elements are built up. The peculiarity of conducting work using this construction technology results in problems of forming “cold” joints associated with ensuring the strength of the adhesion of adjacent layers while simultaneously regulating the required rheological and technological parameters of materials for 3D printing. Most studies concern the operation of cement systems in comparison with gypsum systems due to the difficulties in regulating the setting time and water resistance of the stone. The main directions of research on viscosity modifier agents of mortar mixtures used in the construction market, as well as ways to increase the interlayer adhesion of fine-grained concretes for additive construction production, were considered. Active mineral additives are used to regulate the rheological properties of the mortar mixture. Organic additives can increase the strength of adhesion and adhesion, but require compatibility with other groups of additives. This requires studying the effect of an organic modifying additive and a hydrophobic agent on the adhesive strength with a concrete base.

Materials and methods. The preparation of the solution mixture and the aqueous solution of the organic polyfunctional additive was carried out according to the established mode, taking into account the complete dispersion of the modifying component in water during the subsequent production and storage of test specimens in accordance with the methodology regulated by regulatory documents.

Results. The test results indicate a decrease in the adhesion of the material to concrete when adding a viscosity modifier when used together with a hydrophobic agent, since the interaction at the interface of the mortar mixture with concrete does not ensure the formation of a physical and chemical bond. Also, when introducing a hydrophobic component into the composition of the mortar mixture, a plasticizing effect is observed with an increase in penetrating ability into the inner layers of concrete, which is indicated by changes in the predominantly cohesive nature of the destruction of specimens to adhesive with the appearance of areas with a type of tearing along the base material.

Conclusions. The relevance of ensuring the compatibility of an organic modifier and a hydrophobic agent to ensure the adhesive strength of the material in additive construction production is substantiated and confirmed. The relevance of the topic of further work lies in establishing a rational ratio of a hydrophobic agent and an organic additive to ensure high values of adhesive strength and penetrating ability of the mortar mixture.

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