Corrosion verification experiment of the screw driven into CLT

IRG/WP 17-40816

N Wada, H Ishiyama, S Yamamoto

Japan has abundant forest resources, but we depend on import for 70 percent of the consumed timber. Japan has the vision which promotes the timber self-sufficiency rate 30% to 50% by 2020. Therefore CLT attracts attention as a new timber material. Japan has a climate with high temperature and humidity, and wooden buildings are often treated with chemicals as a measure against biological deterioration of timber. It is the same for the case of CLT. However, chemical treatment for all layers of CLT requires a huge cost. Therefore chemical treatment every each layer is considered. When chemical treatment is carried out for each layer, macrocell corrosion may occur on penetrating screws, due to an electric potential difference generated between the layer chemical treated and the layer not treated. This study aims to expand the limits of wooden buildings, and aims to expand the demand on timber for new applications such as large facilities and middle-high-rise buildings. In this study, we experimentally evaluated the corrosion of screws in CLT which full-layer chemical treatment, each layer chemical treatment (3 layer and 2layer), and without chemical treatment, for verifying the effect of chemical treatment on metal joints. As a result, the following was clarified. 1. It seems that the amount of chemical has more influence on rust of screws. Because screws in CLT with full-layer treatment are most rusted. 2. The macrocell corrosion wasn't observed in this study. However, it seems necessary to do more inspection because the weight remain ratio can't be confirmed only more than about 97 %.

Keywords: CLT, chemical treatment, expand the demand on timber

Conference: 17-06-04/08 Ghent, Belgium

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