In this paper, we consider the possibility of increasing the fireproof efficiency of the intumescent sealant composition for the heat-insulating unit when sealing expansion joints between concrete elements. Fire protection of building structures is a part of the general system of measures to ensure fire safety and fire resistance of buildings and structures. It aims to reduce the structures’ fire hazard and provide them with the required fire resistance. The main objectives of fire protection are: fire prevention, initial flame breakdown, reduction of fire hazards and fire localization. The material we developed may be used to seal closed and drained exterior wall joints or fire control elements; connections between reinforced concrete and bricks; local sealing of various types of cavities with prescribed fire resistance and so on.