Chromated copper arsenate preservative treatment of North American hardwoods - Part 1. CCA fixation performance

We have examined chromated copper arsenate (CCA) wood preservative fixation at two selected temperatures in seven common North American hardwood speci es: red maple (Acer rubrum L.), white birch (Betula papyrifera Marsh.), yel low poplar (Liriodendron tulipifera L.), trembling aspen (Populua tremuloid es Michx.), red oak; (Quercus rubra L.), basswood (Tilia americana L.) and American beech (Fagus granifolia Ehrh). The softwood red pine (Pinus resino sa Ait.) was included for comparison. CCA component fixation was monitored by the expressate method at both 21 degreesC and 50 degreesC under non-dryi ng conditions. Hexavalent chromium (CrVI) and total Cr, Cu and As contents of the expressate were determined at different times during fixation. Based on CCA fixation results it was possible to divide the examined hardwoods i nto a fast fixing group (beech, red oak acid red maple), intermediate group (white birch and red pine) and slow fixing group (aspen, yellow poplar and basswood). The variable fixation rates for the different species could not be directly related to different anatomical and chemical attributes of the studied hardwoods, although there was an apparent relationship with densit y with more dense species fixing faster than low density species. However, the species differences appeared to be mainly influenced by types and amoun ts of extractives in the woods. In red maple, extraction resulted in a slow ing of the fixation late, while the opposite effect was seen in red oak.