Dynamic Transverse Compression of Spruce to Improve the Intake of Preservatives

Eastern white spruce lumber was subjected to dynamic transverse compression prior to impregnation with a waterborne preservative. For heartwood material conditioned to an average MC of 20 percent a deformation level of 10 percent was required to obtain a preservative retention comparable to that achieved after a 2-hour presteaming at 210?F. Best results were obtained with a compression level of 12.5 percent. Average retention was 16.2 lbs./cu.ft. compared to only 10.7 percent for controls and 12.7 percent for steamed material. The average penetrated cross-sectional area was 41.2 percent compared to 30.3 percent and 35.8 percent respectively. For material with an initial MC of 3.0 percent best results were obtained with a compression level of 17.5 percent. This increased the average retention to 10.5 lbs./ cu ft. compared to 8.2 for controls and 9.1 for steamed. The area penetrated was 26.2 percent compared to 15.3 and 22.5 percent respectively. Static bending tests were performed on clear specimens from the preservative treated lumber. For material at 20 percent MC, MOR was reduced 11.2 percent by compression at the 12.5 percent level and 6.8 percent by steaming. Toughness and MOE were not significantly affected by either pretreatment. For lumber at 30 percent MC a deformation level of 17.5 percent reduced MOR by less than 10 percent while steaming reduced MOR by over 20 percent.

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