The progress of damage and service life of wood stakes impregnated with three kinds of copper preservatives were investigated by field stake test at ASUKA in Nara prefecture.
The stakes were made of sapwood of sugi(Cryptomeria japonica D. Don). The dimensions of each stake were 30×30×600mm. The preservatives used were CCA(copper chromic arsenate wood preservative), NCU(copper naphthenate)and copper chitosan.
The service life was estimated on the basis of the biodegradation of the stake observed near the ground. The service life of untreated stakes was 1.7 years in this field. However, the life of many kinds of treated stakes with copper increased to about 10 years when the impregnation of copper was 0.5 kg/m³. And when the impregnation became 1.0 kg/m³, the life increased to about 21 years for CCA treated stakes as against less than21years for other treated stakes.

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