The findings of the known research in the sphere of concretes and concrete mixes chemical modification have been generalized and systematized; the theoretical statements and methodological recommendations in creating high-performance polyfunctional modifiers have been presented. It was demonstrated that the leading role in concrete modification is played nowadays by this class of additives, as their application provides concretes and concrete mixes with a set of prescribed properties for their operation in various conditions. It was pointed out that this sector is especially relevant in mass concreting, as the most widely used in conducting building and repair works and more demanding to the quality of concretes and concrete mixes. The modifiers were classified and the requirements to modifiers with account of their workability and functional use were listed. A high-performance fungicidal polyfunctional modifier for mass concretes, containing a plasticizing agent and hydration and hardening accelerator has been synthesized. The colloid-chemical properties of the obtained modifier and the properties of concretes and concrete mixes with this modifier have been researched.