Grevillea AS A DURABLE STRUCTURAL MATERIAL: Comparative study of the Preservative Treatability of Grevillea and Cypress Timber

ABSTRACT
Grevillea robusta, also called silky oak, is one of the most widespread and popular exotic softwood
tree species in Kenya today. For many years, it has successfully been intercropped with agricultural
crops in rural Kenya, primarily acting as a shade plant to the crops and as a source of fuel wood to
the farmers.
Despite the fact that the wood has admirable timber qualities and huge economic and environmental
potential as a structural timber material, these have hardly been realized due to its low natural
resistance against decay which leads to short durability in service. This has undermined its capacity
as a construction material leaving it only as a choice for minor and temporary wood work
applications.
The objective of this study was primarily to use environmentally friendly wood preservatives and
most suitable methods to assess the treatability of Dry Grevillea wood and determine whether this
can be a solution to its durability problem for use by the rural community.
A field study was conducted to evaluate the current wood preservation practices in Kenya and
establish the appropriateness of the preservatives and methods used for local application in the farm.
The most environmentally friendly preservatives and most favourable methods of preservation for a
rural community were then adopted for the laboratory tests on the treatability of the wood. The
effectiveness of its treatability was evaluated by comparing its absorption and penetration to that of
Dry Cypress, which is resistant to penetration and absorption of preservatives; and to that of green
Grevillea to investigate the effect of moisture on its treatability.
It was found out that the retentions and penetration measurements recorded in Dry Grevillea wood,
generally, were significantly higher than those recorded in Dry Cypress, which is resistant to
absorption and penetration of preservatives. The results of the tests also confirmed that Dry
Grevillea had significantly higher retention and penetration as compared to Green Grevillea wood,
which had higher moisture content.
Hence, Grevillea wood can be effectively preserved and therefore utilized in construction as an
affordable substitute to available expensive timber species normally preferred for construction. It
was also apparent that the treatability of Grevillea was adversely affected by high moisture contents
and the wood preservation methods used.

 

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