The paper deals with the thermal cracking resistance of the unique constructions massive concrete structures during the building period. The paper quotes results of the calculation research of the NPP reactor base slab thermal stressed state and thermal cracking resistance. The concrete hardening temperature impact on concrete thermophysical and deformation properties is taken into consideration. The concrete thermal cracking resistance is measured in accordance with the deformation criterion. Furthermore, the work pays special attention to the safe technological parameters of cold weather concreting purpose. In addition, the article determines the viable sequence and time limits for the heat protection elements removal.