Intumescent Coatings for Fire Resistance of Steel Structures: Current Approaches for Qualification and Design

Intumescent coatings (ICs) are often used for protecting steel buildings during a fire when the structural, aesthetic, and architectural features of the structural members should be preserved. Indeed, ICs form a thin protective layer on the steel surface, that if exposed to fire or elevated temperatures, expands in volume with a consequent reduction in density. Hence, the protective layer captivates heat and protects the structural member from damage or elevated deformation. This reactive fire protection is designed using prescriptive tables, in which the IC thickness is chosen according to the required fire resistance, critical temperature, and section factor of the steel element. These tables are elaborated on the basis of the tests results according to the UNI EN 13381-8 standard, which is the reference for characterizing reactive systems such as ICs. For its reactive nature, this fire protection has to be applied to the structure in a controlled manner, and it is good practice to verify its correct application by measuring thickness and adhesion in situ through regulated methods. The qualification process of IC systems in Italy can be realized through a voluntary certification within the scope of a European technical assessment or by means of a national technical assessment certificate that is mandatory. All these aspects related to qualification, assessment, and design of ICs are often ignored by both designers and manufacturers, especially in Italy. Therefore, this paper describes all the approaches, introducing the main technical differences, in order to provide a sort of guideline on the use of these reactive fire protections.