Fire tests of CLT specimen protected by intumescent paint

Fire tests of CLT specimen protected by water based intumescent paint designed for wood are conducted at DTU FireLab. The tested CLT was 40 mm thick of dimension 250 • 250 mm. The intumescent paint is applied in one to four layers given different layer thicknesses on the specimen. Additionally, a protecting topcoat layer is added for half of the tests as it is recommended by the manufacturer to protect the coating from water and weather conditions. The treated specimen are exposed to different heat radiations in a H-TRIS experimental setup, which originally was build to mimic furnace tests, but also has been applied to coating systems [1, 2]. The time to ignition and the charring rate inside the CLT was determined by thermocouples using the 300°C temperature criterion for the on-set of wood charring. The results were compared to literature values. It was found that the observed average charring rate was about 1 mm/min comparable to similar literature values for CLT, but larger than the recommended charring rate of 0.63 mm/min indicated in the Eurocodes.
It is found that intumescent paint coatings applied on wood provides passive fire protection to CLT, and the coatings ability to decrease the pyrolysis rate substantially. Furthermore, the time to ignition of the wood is increased. It is found that the protecting topcoat has some influence on the performance of the intumescent coatings.
The experiments described here have been conducted by J. A. Wolters as part of his Master thesis on Experimental Analysis of Fire Properties using H-TRIS and PTHFM, January 2020, Technical University of Denmark. His work is greatly acknowledged.