The impact of the aging of intumescent fire protective coatings on fire resistance

The paper is aimed at determining fire resistance of various intumescent fire protective coatings intended for the protection of steel structures dependently on the simulated operating conditions and atmospheric factors having affected the materials for a certain period. Fire resistance was determined upon applying four methods. The first of them was a method of theoretical calculations. The other methods were experimental ones: a) the fire resistance was established upon using samples of steel double-T profiles covered with fire protective coatings; b) the fire resistance was established after aging the samples at a laboratory upon applying the cyclic freezing-thawing; and c) the fire resistance was established after aging the samples in outdoor shed for 12 months with subsequent heating of the samples according to the standard methodology. The statistical analysis of the obtained fire resistance data shows that there was practically no connection between the values of indicators of fire resistance of non-aged samples calculated theoretically and determined in the experimental way and the indicators of fire resistance of aged samples. The mechanism of material aging taking place as a result of simulated operating and climatic factors is similar for all coatings. However, different coatings are differently affected by aging due to their composition and complexity of the structure. Thus forecasting the fire resistance indicators for different coatings after their aging on the base of the values of the primary fire resistance indicator is impossible. However, a strong link had been obtained and an equation usable for forecasting the fire resistance time (determined according to the standard ISO 834 fire curve) after 12 months of operation of the coating in the outdoor shed according to the results of fire resistance of intumescent fire protective coatings after 60 artificial aging cycles at the laboratory had been deduced.