抄録
The deterioration of preservative treated stakes was followed in aboveground, groundline and belowground zones in order to examine the correlation between their durability and exposure years.
Stakes of six wood species were treated with 0.3, 0.4 and 0.5% solutions of di-iodomethyl p-tolyl sulfone (AMICAL 48). They were half buried together with untreated stakes of each species in a graveyard exposure trial. Then, their deterioration by decay and termite attack was inspected every year by visual observation and measurement of compressive strength parallel to the grain.
The results obtained were as follows:
(1) Even in a belowground zone where the highest deterioration was observed in untreated stakes, the stakes treated with 0.5% AMICAL 48 resisted more than six years with the exception of Beihi sapwood and Oshuakamatsu (Fig. 1, (a)∼(f)). Also, the average ratio of residual compressive strength (σc%) of treated stakes other than Oshuakamatsu was kept over 80% level after six years.
(2) The significant correlations between (a) exposure years and grade of damage, and (b) exposure years and σc% were obtained by the regression lines when the deterioration proceeded quickly (Table II). In this case, by examining the regression lines, the durability of stakes could be easily estimated (Fig. 2 (a) (b)).
(3) When the deterioration was slow, these correlations were difficult to be obtained by the regression lines. However, it was proved that durability could be estimated from the regression curves based on the results of continuous observations within a six year period (Fig. 3).
