ABSTRACT Background: Many historical buildings in Iran need to be protected. In many of these buildings, wood is used as a structural element in features such as beam, pile, roof and floor systems. For this purpose, the architectural features of a historical building located in Gorgan (Northern part of Iran) and characterisation of faults, in addition to identification of wood species were conducted. Stress wave non-destructive testing (NDT) was used and wave speed (WS) was measured in tested members to evaluate the decay situation of major wooden beams of building frames and roof truss. After obtaining data related to WS, time of wave transition (TWT) was calculated and compared with control time. Structural elements were characterized in comparison with control time and classified according to decay severity. Results: The results showed that local hardwood species were used for construction of this building. Furthermore, in some parts of the building, there were severely defected structures, thus highlighting the importance of safety. Moreover, WS strongly depended on the types of faults. Conclusion: Due to high relative humidity of climate, wood structures are exposed to faults in the northern region of Iran. However, their general appearance is adequate and acceptable. For better decision making, the TWT should be accompanied by more investigation into the types of defects.

RESUMO Nanopartículas são amplamente aplicadas em compósitos de polímero-madeira (WPCs) nos últimos anos para melhorar algumas das desvantagens das espécies de madeira sólidas. No presente estudo, os efeitos de nanopartículas de ZnO nas propriedades de retardamento do fogo, propriedades físicas e mecânicas da madeira polimerizada de Populus foram investigadas. Espécimes de Poplar foram impregnados com monômero de estireno, contendo quatro diferentes conteúdos de óxido de nano-zinco (ZnO) (0, 0,5, 1 e 1,5%, com base no peso seco do monômero). A microscopia eletrônica de varredura (SEM) revelou homogênea dispersão das nanopartículas de ZnO na matriz WPC. O ZnO melhorou propriedades físicas da madeira tais como a absorção de água e estabilidade dimensional. Além disso, as propriedades mecânicas aumentaram em comparação com as amostras de controle. O processo de impregnação também significativamente melhorou algumas das propriedades retardadoras de fogo, incluindo o tempo de ignição; no entanto, a natureza de inflamabilidade do estireno agravada alguns outros, como a área carbonizada. Concluiu-se que embora a maioria das propriedades foram melhoradas, a aplicação final do WPC deve ser tomada em consideração antes de tomar a decisão sobre a impregnar a madeira de Populus com estireno ou não.

ABSTRACT Nanoparticles have been vastly applied in wood polymer composites (WPCs) in the recent years to improve some of the drawbacks of solid wood species. In the present study, the effects of ZnO nanoparticles on fire retarding, physical, and mechanical properties of polymerized poplar wood were investigated. Poplar specimens were impregnated with styrene monomer, containing four different contents of nano-zinc oxide (ZnO) (0, 0.5, 1 and 1.5%, based on the dry weight of monomer). Results of the scanning electron microscopy (SEM) showed homogeneous dispersion of ZnO nanoparticles in the WPC matrix. Nano-zinc oxide improved physical properties such as dimensional stability and water absorption. Moreover, mechanical properties increased in comparison to the control specimens. The impregnation process also significantly improved some of the fire-retarding properties, including the ignition time; however, the flammability nature of styrene aggravated some others, such as carbonized area. It was concluded that, although most of the properties were improved, the final application of WPC should be taken in to consideration before making decision on whether or not to impregnate populus wood with styrene.

When chemically treating wood products is used to enhance the properties, the distribution of chemicals in the wood can be more important than the amount of chemical uptake. In this research, two moisture contents (MC) (0 and 25%) were used to study the effect of MC on the nanomaterial retention and distribution in cottonwood (Populus deltoides) sapwood treated with nano-titanium dioxide. The wood samples were impregnated by a full-cell process at three levels of nano‐TiO2 concentration: 0,5; 1 and 1,5%. The nanomaterial retention was calculated and SEM images were used to investigate the distribution of nanoparticles in the wood. The results showed that increasing the nano-TiO2 concentration caused more retention and the MC difference caused almost identical retention at 0,5 and 1% concentrations. Although the retention in the 0% MC samples was slightly more than those of 25% MC, this retention was significantly more in these samples (0% MC) at 1,5% concentration. SEM images indicated that the nanoparticles had more uniform distribution in the 0% MC samples than the 25% MC ones and the difference was clearly visible at 1,5% concentration. Low MC ranges (about 0%) are better than high MC’s to impregnate cottonwood samples with nano-TiO2 by using the full-cell process.

The aim of this study was to investigate the decay resistance of particleboards treated with nano- zinc oxide against the white-rot fungus Trametes versicolor and the brown-rot species Coniophora puteana. The nanomaterial was used for manufacturing particleboards at 5, 10 and 15% wt based on the glue dry weight. The soil block decay test was performed according to ASTM D 1413 (2007) using a 12 weeks incubation period. The results showed that all treated boards had good resistance against the decay fungi and the weight loss decreased in the samples with increasing nanomaterial loading. The threshold level of treated boards against fungal decay was obtained about 21% and 17% nano-ZnO against C. puteana and T. versicolor, respectively. Therefore, it had a positive effect on increasing particleboard resistance against the fungi. The maximum decay resistance (or minimum weight loss) occurred in the samples containing 15% zinc oxide nanoparticles.