Tests on intumescent paints for fire protection of existing steel structures

Intumescent coatings (i.c.) are often used on steel structures to reduce the heating during a fire when the structural, aesthetic, and architectural value of the structural members should be preserved. Indeed, i.c. form a thin protective layer on the surface. When the i.c. are exposed to fire or excessive heat, volume expansion and density reduction take place. Therefore, the protective layer absorbs heat and protects the structural member from damage or excessive deformation. To perform rigorous and realistic analyses on protected steel members, thermal properties of all materials, including i.c., should be known. Nevertheless, the thermal properties of these systems are not available, especially for existing buildings. This paper shows experimental test on steel members protected with i.c., taken from an existing structure, which is thirty years old. I.c. thickness measurement and adhesion tests were performed in situ, whereas furnace tests were carried out at the Laboratory of the Italian National Fire Services. The tested steel members have various section factors and behave two fire curves (Standard Fire and Smouldering Fire) during the tests in furnace. The furnace tests were performed on steel members with original i.c. (reference) and steel members protected by applying a new i.c. after removing the existing paint (restored) or simply by applying it on the existing paint (repainted). The results show that the existing i.c. is not very efficient, whereas the restored and repainted specimens showed similar performance. A law for the thermal conductivity of the i.c. was obtained from the experimental results, according to an European code, and used in a finite element numerical model