ACA and CCA preservative treatment and redrying effects on bending properties of Douglas-fir

This report evaluates the effects of two waterborne preservative treatments, ammoniacal copper arsenate and chromated copper arsenate, and subsequent redrying at temperatures of < 170°F (77°C) on the bending properties of small, clear specimens of Douglas-fir. In addition, we studied the possibility of a differential effect on bending strength resulting from differences in initial treatability of specimens. At redrying temperatures of up to 170°F, ammonical copper arsenate had no significant negative effect on bending properties at three levels of retention (0.34, 0.41, and 2.29 pcf (5.4, 6.6, and 36.6 kg/m3)). Conversely, for material treated with chromated copper arsenate at 0.6 pcf (9.6 kg/m3) and redried at 170°F, mean modulus of elasticity, modulus of rupture, and moment-carrying capacity were significantly reduced. Initial treatability of specimens did not influence the effect of treatment on bending properties.