Influences of drying treatments on bending properties of plantation-grown white spruce

Influences of drying treatments on bending strength properties of plantation-grown white spruce lumber were studied. One hundred and ninety pieces of nominal 2 by 4 structural lumber were divided into four groups. One group in the green condition was used as a control, and the other three groups were dried to a target moisture content (MC) of 12 percent using mild, moderate, and harsh conventional drying schedules. Modulus of rupture (MOR) and modulus of elasticity (MOE) of each specimen were determined using a four-point bending arrangement. The conventional drying treatments significantly influenced bending strength and stiffness of lumber. The mildly dried material represented the maximum strength increase, with average ratios of dry to green 1.55 for MOR and 1.44 for MOE. Harsh drying conditions reduced the ratios to 1.15 and 1.22, respectively. Thus, the more severe the drying condition, the smaller the ratios. It was also found that the low visual stress grade material in this research was less sensitive to MC change than the high visual stress grade material.

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