T. Stevanovic-Janezic, P.A. Cooper, Y.T. Ung
Chromated Copper Arsenate Preservative Treatment of North American Hardwoods. Part 2. CCA Leaching Performance
Summary
Seven North American hardwood species were vacuum or vacuum/pressure treated with 2% CCA-C
solution and fixed at temperatures of 21°C and 50°C under conditions of high relative humidity (95%).
The rates of fixation results are presented in Part 1 of this study. Red maple (Acer rubrum L.), red oak
(Quercus rubra L.), American beech (Fagus grandifolia Ehrh), white birch (Betula papyrifera Marsh.),
trembling aspen (Populus tremuloides Michx.), basswood (Tilia americana L.) and yellow poplar (Liriodendron
tulipifera L.) were evaluated. The softwood red pine (Pinus resinosa Ait.) was included for
comparison. Adequately fixed wood blocks (99.9% chromium reduction) were exposed to leaching by
the AWPA E11 procedure. All CCA components were leached in high quantities from oak wood, while
from red maple and beech, high arsenic leaching occurred. Leaching losses from aspen, basswood and
yellow poplar were low and comparable for both fixation temperatures. In most species, the amount of
leaching was affected by the treating method, with lower leaching from pressure treated wood blocks
than from vacuum treated blocks. Removal of extractives from maple and oak blocks before treatment
affected the CCA leaching performance in these species. Extracted red oak had lower chromium and copper
leaching, but higher arsenic leaching. In contrast, extracted red maple had reduced leaching of all
CCA components compared to unextracted wood.
The examined hardwoods can be classified into three groups according to their CCA fixing and leaching
characteristics: fast fixing/high leaching group (beech, red oak and red maple), intermediate fixation
rate and leaching group (white birch and red pine) and slow fixing and low leaching group (aspen, yellow
poplar and basswood).
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 55, 12/2001
Pages: 7 - 12
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