Waterborne preservative treatability of tamarack (Larix laricina (Du Roi) K.Koch)

IRG/WP 98-40112

A Taylor, Y T Ung, P A Cooper

Eastern larch or tamarack (Larix laricina (Du Roi) K.Koch) lumber from New Brunswick, Canada was evaluated for preservative treatability with chromated copper arsenate (CCA-C) and ammoniacal copper arsenate (ACA). The fixation and leaching characteristics of CCA-C treated tamarack sapwood and heartwood were also evaluated. CCA-C penetration into both sapwood and heartwood was poor. ACA fully penetrated the sapwood but penetrated the heartwood only marginally better than the CCA-C. The rate of CCA-C fixation, as defined by the rate of reduction of hexavalent chromium, varied greatly between sapwood and heartwood and between different heartwood samples. Heartwood fixed much faster than sapwood, averaging 2-3 days at 21°C and 5-6 hours at 50°C compared with 15-20 days and 30-35 hours respectively, for sapwood. The fixation rate was directly related to the hot water soluble extractive content of the wood. The quality of fixation, as defined by resistance to leaching of the CCA-C components, was much lower for the faster reacting heartwood. The combination of poor penetration and low CCA-C stability in tamarack heartwood suggests that this preservative is not appropriate for this species.


Conference: 98-06-14/19 Maastricht, The Low Countries

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