Effect of treatment schedules on CCA penetration and retention in different sized eucalyptus utility poles
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ABSTRACT Air seasoned treated eucalyptus utility poles are the most commonly used for transmission and telephone lines in Uganda. However, there have been frequent reports about the failure of CCA treated poles while in service that has been attributed to the preservative chemical, method of treatment or wood species used. The objective of the study were to determine the effect of initial vacuum duration on CCA penetration and retention in eucalyptus pole sizes and to determine the effect of pressure duration on CCA penetration and retention in different eucalyptus pole sizes. A total of 540 Eucalyptus grandis poles i.e. 180 poles in each category with an average moisture content below FSP (28%) were assessed and treated differently according to their size that is to say 9, 10 and 12m in length. Each charge contained poles of the same category size. Full cell pressure treatment process was used to treat the charges using CCA preservative. Initial vacuum time and pressure time were varied in all the pole sizes. CCA penetration and retention increased with increase in initial vacuum and pressure time in all pole sizes. 9m poles attained the lowest penetration and retention values for all the parameters while 12m poles attained the highest. Initial vacuum time of 15minutes and pressure time of 60 minutes gives adequate penetration and retention values and should be put into practice in order to ensure maximum protection of the wood hence increasing their service life. More research however, is needed to be conducted on other eucalyptus species including their hybrids and in determining the longest vacuum and pressure durations beyond which there is no change in penetration and retention.