The issue of shrinkage deformationsDeformation is inherent in a wide range of building materials, the basis of which is cement stoneCement stone. Shrinkage can cause significant internal stresses in cement stoneCement stone, which is the cause of formation of characteristic shrinkage cracks and subsequent failure of materials and goods. The objective of this study is to experimentally investigate the influence of a complex expanding additive consisting of alumina cement and natural gypsum on the deformationDeformation processes of materials on cement binders. The resultsResult of the study are presented in the form of dependencies, which demonstrate that a significant influence on the expansion value is exerted by the composition of the expanding additive, which is characterized by the content of sulphur oxide and aluminium oxide. The obtained functional dependences of composition deformations on the content of sulphur oxide in the presence of polymerAdditive additives allow for the prediction and control of expansion deformationsDeformation in polymer cement compositions for cement building materials considering the influence of various modifying additives.