The paper presents the research results on the development of scientifically valid compositions of 3D printing construction mixes with improved performance characteristics. To regulate the physical, mechanical and technological properties of cement-based mixes, thermallymodified peat additive MT-600 is developed. The paper studies the world experience in the construction additive technology field. The experimental results are presented for cement paste and construction mixes with MT-600 additive for 3D printing. It is established that using the proposed fine additive increases the strength of the cement paste at early stages of hardening, which is the determining factor in the formation of building and technical characteristics for 3D printing. The X-ray phase analysis is carried out for the new composition of cement paste modified with MT-600 additive, which allows studying characteristics of the structure and properties of construction mixes during the hardening process.