EFFECTS OF AMMONIACAL COPPER CITRATE PRESERVATIVE TREATMENT AND REDRYING ON BENDING PROPERTIES OF 2 GRADES OF SOUTHERN PINE 2-BY-4-LUMBER

Ammoniacal copper citrate (CC) is a new preservative recently accepted in many American Wood Preservers' Association standards. This study e valuated the effects of CC preservative treatment on several mechanica l properties of two grades of southern pine dimension lumber. For the Dense Select Structural grade lumber, the effects of CC treatment were generally found to be similar to previous reports for chromated coppe r arsenate and/or other ammoniacal copper preservative treatments - CC treatment to a target retention of 6.4 kg/m(3) (0.4 pcf) caused an av erage reduction in modulus of rupture (MOR) of only about 5 percent, n o reduction in modulus of elasticity (MOE), and a reduction in work to maximum load (WML) of 7 to 18 percent. Reductions in MOR and WML were greater in samples kiln-dried after treatment. Treatment to the marin e retention of 30 kg/m(3) (2.5 pcf) caused larger reductions in WML. H owever, for the No. 2 grade lumber, the effects of CC treatment on MOR were greater (average reduction of 12%) than those noted for Dense Se lect Structural grade lumber. These effects were also slightly greater than those previously reported for chromated copper arsenate treatmen t. No comparative data on No. 2 grade material were available for othe r preservative systems based on ammoniacal copper. As the popularity o f arsenic-free ammoniacal copper-based systems increases, this phenome non of greater strength loss with No. 2 grade treated lumber deserves additional study.