Combining mineralisation and thermal modification to improve the fungal durability of selected wood species

The development of non-biocidal and environmentally friendly systems to protect wood against biological decay has become a high priority in recent years. In the present study the impact of an innovative modification procedure, combining two environmentally friendly modification methods: thermal modification and mineralisation, using an aqueous solution of calcium acetoacetate as a precursor, on the fungal durability of wood was evaluated. European beechwood (Fagus sylvatica) and Norway sprucewood (Picea abies) were selected as model wood species. Wood samples were treated using either a single or combination of both methods and exposed to four different fungi: Gloeophyllum trabeum, Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus. The effect of the different modifications on moisture content, dynamic vapour sorption, contact angle and pH value was also evaluated. Overall, the highest durability against Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus was achieved through thermal modification in both wood species, while the combination of mineralisation and thermal modification has a synergistic effect against degradation by Gloeophyllum trabeum. In the case of beechwood the mass loss decreased from 41% for native to 6% for combined modified samples. We proved that the effectiveness of different treatment against fungal decay of wood were in strong dependence of their moisture content, dynamic vapour sorption, contact angle and pH values. The role of fungi on the morphology of the wood and on crystal structure of formed carbonate was investigated using SEM-EDS analysis.