Intumescent fire protection coating


Development of an intumescent fire protection coating for ultra-high performance concrete (UHPC)

© Fraunhofer WKI
UHPC slab with BB3 fire protection coating following fire exposure in a laboratory.

Ultra-high performance concrete (UHPC) is a very densely textured concrete with a compression strength similar to steel at up to 250 N/mm². It is up to ten times as hard as common concrete. When exposed to fire, UHPC can burst open explosively due to the sharply rising temperature. This behaviour is largely influenced by the mass transfer of water, steam and air through the concrete’s pores. When there is a fire, the pressure in the pores increases. The very high density of UHPC promotes this process and the result can be a premature loss of load-bearing capability. As part of a DFG project run by the iBMB at the TU Braunschweig, methods were sought to minimize bursting due to fire exposure and thus to achieve overall improvement to fire protection for UHPC.

The researchers in the Department of Structural Engineering and Construction had the task of finding out whether the successful high-performance fire protection coatings developed for wood could offer approaches for solutions. The idea was to minimize the temperature increase by using an intumescent fire protection coating. If the temperature increase is slower (especially during the beginning of a fire), then the temperature gradients at the outer areas of a concrete structure could be reduced. This would then allow a reduction of the pressure in the pores which causes the tension and leads to bursting.