Nondestructive prediction of fire performance in fire retardant-treated wood using x-ray computed tomography

The fire performance of fire retardant-treated wood can be evaluated based on how much of the chemical retardant is used. Therefore, methods for identifying chemical content in wood are needed. Stereo images of wood samples before and after the fire retardant treatment were captured using micro-focus X-ray computed tomography. Image brightness values, indicating concentration, were calculated using binarized images sliced from the X-ray images. Changes in integrated brightness values before and after treatment showed a strong positive correlation with chemical content at a 1% significance level. The chemical content of the retardant-treated wood was predicted based on the relationship between the two. The predicted values were in agreement with the values measured using the leaching method. Fire performance tests of the fire retardant-treated wood were conducted using a cone calorimeter. The treated wood was classified as fire-retardant and non-combustible wood. In addition, the fire performance predicted by the relationship between changes in integrated brightness values and chemical content agreed with the classification by the fire performance test. These findings suggest that X-ray computed tomography can be potentially used to predict the chemical content of fire retardant-treated wood.