Microwave modification of Radiata pine railway sleepers for preservative treatment

The use of hardwood railway sleepers in Australia is limited by hardwood timber resources, thus softwood sleepers made from plantation Radiata pine (Pinus radiata) may replace them. Low permeability pine heartwood does not allow for good impregnation with preservatives. Microwave (MW) wood modification increases heartwood permeability and improves preservative distribution and uptake. The experimental study of MW sleeper modification and impregnation, allows for the rational MW process parameters and preservative treatment schedules to be determined, with an estimate of the effect of MW treatment on sleeper quality, and for recommendations to be provided to industry. On the basis of the research results a 400 kW commercial MW plant capable of an output of 100,000 sleepers per annum has been designed. The costs of MW sleeper processing are acceptable to industry and provide good opportunities for the commercialization.