Thermal Degradation and Charring Rate of Corymbia Citriodora and Eucalyptus Grandis Wood Species

This research reports an investigation of the potential of Eucalyptus grandis and Corymbia citriodora for structural applications in civil construction with an emphasis on the wood-charring process in fire condition. Published data on wood carbonization to determine the charring rate for structural propose are sparse in Brazil as there have been only a few studies in this direction. The rate at which the wood converts in char is determinant to evaluate the fire endurance, because the failure of wooden structural elements and its composites exposed to fire occurs through reduction of cross section. The fire resistance depends on cross sections dimensions that are gradually reduced when exposed to fire. Several tests were performed to evaluate the variables that mostly affect the charring rate. The chemical composition, shrinkage, thermal gravimetric analysis (TGA) and measurements of calorific value were also performed. The TGA results indicated that both species were stable up to 250oC. The average calorific value of Corymbia citriodora was slightly less than that of Eucalyptus grandis, whose value was 17849J/g. The chemical analysis revealed that Corymbia citriodora had approximately three times more ash and about 4% more content of extractives than Eucalyptus grandis. The latter had almost 6% more lignin and 2% more cellulose than Corymbia citriodora, but 8% less hemicelluloses. The charring tests showed that both woods had similar charring rates. In addition, statistical analyses showed that shrinkage and lignin content are the main factors affecting the charring process.