This paper proposes an analytical method to calculate the thermal conductivity of fully expanded intumescent char after undergoing various cycles of accelerated aging. To investigate the accuracy of this thermal conduetivity model

hydrothermal aging tests and fire tests were conducted.Expansion ratio

poresize and steel temperature were measured.An obViOUS trend is that as the number of hydrothermal aging cycle increased

the pore sizes in the expanded intumescent chfir tended to become bigger.This has the effect of increasing the thermal conductivity of the intumescent char

reducing its thermal insulation performance and increasing steeI temperature.Using this thermal conductivity model and the measured bubble diameters for two types of intumescent coating after different cycles of hydrothermal aging

the intumescent coating inSUlated steel plate temperatures were numerically caIculated and compared with measured re Sults. The agreement was found to be generally satisfactory

suggesting that the thermal conductivity model is acceptable.