A Comparison of the Durability of Two Stake Sizes in Southern Mississippi

摘要

The small stakes used in preservative evaluation are thought to accelerate deterioration relative to larger in-service members, but the extent of the acceleration is poorly understood. This paper compares the durability of the commonly used 19- by 19-mm stakes to larger 38- by 89-mm (nominal 2 by 4) stakes that more closely resemble commodity-size material. The years to reach average ratings corresponding to loss of 10% of the cross section or complete failure were compared for 53 sets of matched 19-by 19-mm and 38- by 89-mm stakes exposed in plots near Saucier, Mississippi. The larger stakes required an average of 2.1 times longer to reach an average rating corresponding to loss of 10% of the cross section, but this ratio ranged from as low as 1.0to as high as 8.0. It took an average of 2.2 times longer for the larger stakes to fail, with maximum and minimum ratios of 3.5 and 1.4, respectively. The efficacy of the preservative system appeared to have little consistent effect on relative longevity of the two stakes sizes. Linear regression of average years to loss of 10% of the cross section or failure for the two stake sizes yielded R2 values of 0.60 and 0.69, respectively. The data indicate substantial uncertainty in using the durability of 19-by 19-mm stakes to predict the durability of 38- by 89-mm stakes, and by extension, the durability of in-service members.