Adhesive technology is considered the innovative joining technology of the 21st century. The bonding of reinforcing materials to an existing concrete structure is the subject of EN 1504-4 "Products and systems for the protection and repair of concrete structures, Part 4: Adhesives for construction purposes". The bonding of steel plates or other materials to reinforce concrete structures, the bonding of hardened concrete to hardened concrete or fresh concrete to hardened concrete is the focus of this standard. Reaction resins based on epoxy resin, PMMA, polyester, etc. are used.