EFFECT OF AGING AND TEMPERATURE ON THE RESISTANCE TO SPUR PENETRATIONIN RED PINE POLES TREATED WITH CCA-PEG-1000

The aim of this study was to measure the effect of aging and temperatu re on the resistance of wood fibers to the penetration of linemen's sp urs in utility wood poles. The measurements are made by simulating the principal movement of the spur in penetrating the pole on a mechanica l test bench. The comparison involves specimens of wood distribution p oles impregnated with a mixture of copper, chromium, and arsenic oxide s containing polyethylene glycol with an average molecular weight of 1 000. The results show that twice as much force is needed to drive the spur into the wood to a given depth when the outer-shell moisture cont ent drops from 35 to 10 percent (800 N vs. 1600 N). Pole aging over a period of 4 years would result in a 62 percent increase in this force (1079 N vs. 1752 N) for specimens with a moisture content at in-servic e equilibrium. As for the temperature effect, the measurements at -35 degrees C revealed a 23 percent increase in the force compared to tho se at the ambient (1079 N vs. 1327 N). Although these effects are not necessarily cumulative, they could affect the climbability of a pole. Meanwhile, measurements on a few specimens treated with pentachlorophe nol in oil show only a slight sensitivity to in-service pole aging. On ly the low-temperature environment (- 35 degrees C) increases the forc e required to drive the spur in the wood, by a value equivalent to the previous case. The chemical analyses allowed a relation to be establi shed between the fiber resistance to penetration and the aging of the CCA-based specimens. The hardening of the wood could be attributed to the rapid leaching of polyethylene glycol in the area of spur penetrat ion (loss of 71% in 24 mo. in the outer shell). Last, the mechanical t est bench proved to be a far more sensitive instrument than the Pilody n 6J for keeping track of variations in the pole surface hardness over time.