Treating and Drying Composite Lumber with Waterborne Preservatives–Part 2: Joist Treating and Drying

Southern pine composite joists were made with several types of core to determine treatability and drying characteristics. Southern pine veneer was used on the edges. The joists were impregnated commercially with CCA preservative in two charges to a target retention of 0.60 pound per cubic foot (pcf). Treatment was followed by kiln-drying in the laboratory using two schedules. Retention of preservative in composite joists compared very favorably with retentions of sawn joists treated in the same charge. Ninety percent of the retentions for the composite joists exceeded 0.54 pcf. The composite joists dried rapidly without defects and matched the sawn joists in moisture loss rates. Drying to 10 percent moisture content required 4 to 7 days depending on the severity of the kiln-drying schedule. No delamination of veneer or veneer-core joints occurred. No warp appeared in the composite joists but even the best of the sawn joists (No. 1 Common) exhibited slight warp. Appearance was uniformly good in the composite lumber. Absent were the knots, pitch streaks, and stain, typical of sawn lumber, particularly No. 2 Common and lower grades of southern pine.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member