Bui Van Ai, Truong Quang Chinh, Dinh Van Tien
Forest Science Institute of Vietnam
In Vietnam, there is an increasing demand of using timber as materials for house building and poles for cultivation, and for electricity and telephone poles. Some types of forest grown timbers, such as eucalyptus and acacia, have a mechanical nature meeting the demands of use in basic construction; however, their timbers are easily harmed by insects and fungi. In order to use forest grown timbers permanently in severe conditions, it is necessary to conduct research to specify appropriate methods for timber preservation with simple technical requirements and easily applicable in mountainous and countryside areas.
Materials and method
– The 10 kinds of forest grown timbers including acacia, eucalyptus and ficus religiosa were researched to specify their natural durability. The 3 types of timbers including Acacia auriculiformis x Acacia mangium, Acacia auricumliformis and Eucalyptus urophylla are researched to specify the possibility of preservative seepage. The preservative used in the research is XM5.
– Evaluate the natural durability of forest grown timber and the timber preservation effect of XM5 in the natural experiment ground based on how much destruction was caused by worm and fungi on the experimental timber sample.
– Experimentally arrange and plan whole factors to survey the possibility of preservative seepage of forest grown timber to affected factors such as: Wetness of timber, time of soaking, pressure of soaking and solution concentration of preservative according to soaking methods such as Normal soaking, diffuse and vacuum pressure.
Result on specifying durability of some types of acacia and eucalyptus timbers in the natural experiment ground: The Timber sample of 10 types of acacia, eucalyptus and ficus religiosa are all completely rotten and destroyed by fungi and insects after 3 years in the natural experiment ground. Therefore, timbers of acacia and eucalyptus are ranked into the timber group with bad to very bad durability.
Research on the possibility of preservative seepage of some kinds of acacia and eucalyptus timbers:
Having established the correlative equation between the amount of preservative seepage (Kg/m3) of 3 types of timbers and affected factors are wetness of timber (W), time of soaking (T), pressure of soaking (P) when using normal soaking and vacuum pressure. Correlative equation is used to specify specifications of timber preservation process according to each method.
Effect of timber preservative XM5 using in construction and making outside poles: The samples of sawn timber preserved with 2 kg/m3 higher amount of preservative seepage have unchangeable durability index in the initial 2 years (gain 100); however, in the third year, the durability index reduced, gain over 90. In comparison the control sample which was not preserved has been completely destroyed. Samples of junks are preserved by XM5 according to diffuse method, after 8 year experiment, it still gain the durability index over 70.
Conclusions
– Species of acacia and eucalyptus are ranked into the natural durability from bad to very bad.
– Having specified the possibility of preservative seepage in 3 types of timbers such as Acacia auricumliformis, Acacia auriculiformis x Acacia mangium, and Eucalyptus urophylla according to normal soaking and vacuum pressure methods. Acacia auriculiformis x Acacia mangium timber has good possibility of preservative seepage, Acacia auricumliformis and Eucalyptus urophylla has possibility of preservative seepage.
– Having proposed two technical processes of forest grown timber preservation used in construction and for making outside poles according to normal soaking and vacuum pressure methods.
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