Penetration and Retention of CCA Preservative in Eucalyptus grandis, and Eucalyptus clones Gu7 and Gc550

Abstract

Wood preservation is essential especially in wood that is to be subjected to outdoor use. Furthermore, utility poles must be chemically treated to enhance their service life as they are known to be subject to decay and insect attacks while in field. There are many treatment processes on the scene although pressure treatments with preservatives like CCA and creosote are regarded most effective. These treatments are known to improve pole service life by over 50 years if properly administered and maintained. Losses caused by premature pole failures in the field can be avoided if; the correct treatment methods, right pole species and preservative are used. These losses incurred include; costs for replacement of the failed poles, compensations in case of accidents, as well as disposal of the chemical wastes from these failed poles. This study was carried out to assess the penetration and retention of CCA preservative in Eucalyptus grandis and Eucalyptus clones, GC550 and GU7. The objectives of this study were to determine the sapwood depth of E. grandis, GU7 and GC550 poles, to assess the penetration of CCA in E. grandis, GU7 and GC550 poles and to determine the retention of CCA in E. grandis, GU7 and GC550 poles. A total of 105 poles were used, 35 poles from each species, assessed for sapwood depth after chemically treated with CCA preservative using the full cell pressure method. The treated poles were then assessed for penetration and retention of CCA using sample borings from each pole sample. The results showed that E. grandis poles had the largest sapwood depth, highest CCA penetration and CCA retention followed by GU7 poles and lastly GC550 poles. The large sapwood favored the high CCA penetration since sapwood cells are porous, and the high CCA retention was due to its positive correlation with penetration. A conclusion was drawn that E. grandis poles with large sapwood depth are better field performing since a larger proportion of their girth is chemically treated making them durable while in the field. E. grandis was therefore suggested as the better option for utility poles over the clonal poles.