Impregnation of roundwoods by sap-displacement in Madagasca
IRG/WP 352 E
M Fougerousse, P Guéneau
The use of roundwoods is already very important in Madagascar and steadily increasing for the following applications: - posts, electricity and telephone line supports (medium voltage) - stakes, piles for civil engineering structures, bridges, gantries, road and port works, etc. - construction of houses (posts, frameworks, piles, etc.) and rural buildings (sheds, stables, piggeries) - fence posts, vine stakes, posts for cattle pens, etc. As in all tropical, climates, the agents of destruction of standing timber are numerous and very active. Under these conditions, the natural durability of currently used species does not exceed a few years. It is necessary therefore to consider treatments for securing prolonged service life, without too much cost increase, so that users do not choose substitutes such as metal or concrete. The treatments in pressure vessels can only be applied, from an economical point of view, in regions near impregnation plants. But rural areas, too remote and badly served by transport, cannot be supplied in this way, because of the high transportation cost which has to be added to that of the treatment. This is why for a long time attention has been given to treatment processes and preservatives which can be applied without industrial equipment, at small scale sites, scattered eventually mobile. For a reasonable cost, these techniques confer to the wood a sufficient resistance to the agents of destruction, the most virulent of which are decay fungi and termites, in some cases both, depending on the area. Research in this direction has been carried out on the treatability of some Madagascan species using sap displacement.