Mechanical resistance of intumescent coating

The project stems from a problem encountered in a previous COWI-Fonden project, where we studied the fire protection of bridge cables. While the project was focusing on the fire performance of epoxy intumescent coating (IC), the test results indicated that a major issue in effectively using such paint for protecting bridge cables from fire would be the possible detachment of the paint, rather than the fire performance of the paint itself.
Such detachment may be caused by large deformation, vibration, mechanical friction of inspection machinery, etc. However, the exact role played by these factors is unknown, as well as the extent of the damage they can cause on the insulation.

Problems related to the unexpected mechanical failure (cracking, detachment, fall-off) of ICs have also been witness in other experiments at DTU, e.g. during the expansion of the IC on circular and rectangular hollow profile, as a consequence of tensile stresses arising in the expanding char.
IC can also be easily damaged at ambient temperatures, by the occurrence of accidental events, such as earthquakes, explosions, or even local impacts. Previous studies at DTU have indicated that even a limited and local damage of the insulation at the bottom of columns (which typically experience the largest deflection during e.g. an earthquake) may reduce the fire resistance of the structure significantly, putting the fire brigades at high risk during their intervention in a possible following fire.

For the reason above, it is essential for the safety of steel structures and development of the steel and IC industry to gather information on the mechanical failure of ICs.
This project is aimed at bridge this gap by means of an experimental campaign at DTU laboratories that accounts for both mechanical tests at ambient temperatures and coupled mechanical and thermal test. The outcomes of these tests are expected to lead to relation between the deformation in the steel and the extent of damage in the IC. In particular, the project is also aimed at identifying, for each type of IC studied, different insulation thicknesses, and shape of the profiles, the maximum admissible value of steel deformation, which ensure the integrity of the IC.
This value can be readily used by designers, who could better choose the type and thickness of the insulation on the basis of the steel profiles used and the expected structural deformation.