Influence of Component Fractions and Structure Characteristic on the Combustion Behavior of Densified Wood

Densified wood (DW) is a promising structural material in high-rise timber buildings. However, fire safety issues restrict its applications. The key is to understand the influence of component fractions and dense structure on DW combustion. Here, the combustion behavior of DW is experimentally and numerically investigated. Thermogravimetric analysis (TGA) results showed that DW has 29 K earlier and 1.01 x 10-4 s � 1 lower peak mass loss rate, 5 % higher residue mass than natural wood (NW) due to the component weight fraction changes by delignification. ThermaKin was applied, combined with TGA, differential scanning calorimetry and microscale combustion calorimetry, to obtain pyrolysis kinetics and thermodynamics of wood. Cone calorimeter tests showed DW has delayed ignition time because its high density enhances heat conduction and decelerates wood surface temperature increase. DW has delayed but higher value of second heat release rate peak and lower heat of combustion due to its dense structure leading to a thermally insulating and condensed char layer. Radial thermal conductivity of wood linearly increases with density. Temperature poses greater impact on thermal conductivity than density. An optimized thermal conductivity equation is proposed and applied to predict the cone calorimeter tests, yielding good agreement.