PERMEABILITY AND MECHANICAL BEHAVIOUR OF MICROWAVE PRE-TREATED NORWAY SPRUCE RIPEWOOD

Abstract

This is a studyofthe influence of microwave (MW) pre-treatment on the permeabilityof Norway spruceripewood(Picea abiesL. Karst)as it affects its mechanical properties. Specimens weretreated under variable moisture content,MW intensity,and impregnation processes. According to the results,thespecimens withaninitial moisture contentof 45–65% exhibited the highest permeabilityvaluescompared to referencesamples. Aninsignificant difference was found between MW pre-treatments at2 and3kW.Statistically significant results were found afterlong-time (24h) vacuum-pressureimpregnation(LP). Theaverage retention value followingLP was 132 kg.m-3, which isalmost threetimes greater thanthe MW-treatedgroupsimpregnated in ashort-time vacuum-pressure process. The average depth of penetration after LP was 2.0mm and the proportion of the impregnation area followingLP was 17.6%. MW pre-treatment had no effect on the impregnability or the mechanical propertiesof the wood; other MW regimes are open for further examination.