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Summary
Round posts and wood samples from fast-grown planted trees, irrigated with sewage effluent, only five years of age, at Mildura, Victoria, were tested for basic density, strength properties and preservative absorption.
The full range of tests were made with Eucalyptus grandis (flooded gum) and E. botryoides (southern mahogany), whereas only density measurements could be carried out on Casuarina cunninghamiana (river she-oak) because of severe splitting of the post sections on drying. It is unlikely that marketable round posts can be produced from trees of this species grown under such conditions.
The proportion of sapwood in trees of all three species was found to be high, and density values were considerably lower than those for the heartwood of butt logs from mature trees of the same species. However, measurements of maximum load and modulus of rupture showed that strength properties were sufficiently high for posts of these two eucalypt species to meet any strength requirements for fencing.
The sapwood of both eucalypts was found to be easily and uniformly penetrated under pressure with either CCA or creosote preservatives. Sap replacement treatment, on the other hand, although producing adequate retentions, gave variable penetration patterns.