Treating and Drying Composite Lumber with Waterborne Preservatives–Part 1: Short Specimen Testing

Two groups of composite lumber with a particleboard core and veneer surfaces were fabricated to determine the treatability of this material with waterborne preservatives. One group was made from particleboard and veneer of southern pine, which is easy to treat. The second group was made from heart Rocky Mountain Douglas-fir, which is very hard to treat. Two waterborne preservatives, chromated copper arsenate (CCA) and ammoniacal copper arsenate (ACA), were used to treat specimens 2 by 4 by 18 inches to target retentions of 0.25, 0.40, and 0.60 pound per cubic foot. Target retentions were achieved uniformly at all retention levels. Untreated controls of both species were also prepared. Soil block tests and chemical retention analyses were conducted in the laboratory; long-term stake burial tests are in place at the USDA Forest Service’s Mississippi outdoor exposure site. Weight losses of the southern pine in soil block tests decreased as retention increased. Composite lumber was treated and redried with little or no swelling.

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