Davor Kržišnik

Thermal modification of wax-impregnated wood to enhance its physical, mechanical, and biological properties

Abstract Thermal modification is the most important commercial modification procedure. Thermally modified (TM) wood has improved durability, but its performance does not meet expectations predominately under moist conditions. To reduce water uptake of TM wood, Norway spruce specimens were treated with suspensions of a natural wax by dipping impregnation (DipI) or by vacuum-pressure impregnation (VPI). Wax-treated specimens were subsequently TM at 185, 200, 215, and 230°C. Control specimens were heated up to 100°C only. Contact angle (CA), short-term and long-term water uptake, bending strength, and performance against wood decay fungi of the resulting material were determined. The results show that a combination of wax treatment and thermal modification have a synergistic effect that considerably improves hydrophobicity, reduces liquid water uptake, slows down water vapor uptake, and improves the resistance against fungal decay of the treated material.

Performance of wood in the Franja partisan hospital

ABSTRACT Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades. In order to enable even more extensive and reliable use of wood, factors affecting wood’s service life need to be understood. It is well known that fungal degradation of wood is predominantly affected by moisture content (MC) and temperature (T). In order to elucidate the influence of these two factors, long-term monitoring of T, relative humidity (RH) and wood MC was carried out at the WWII partisan hospital Franja, Slovenia. The results clearly showed that fungal degradation of wood is influenced by MC and T. A model to predict brown and white/soft rot decay of wood was applied to predict the expected service lives of different building components of the hospital cabins. The predicted times until onset of decay were well in accordance with findings made during visual assessments and drill resistance measurements at this historical site. The monitoring concept in combination with a mathematical decay prediction model can provide accurate data and valuable guidance for building modern structures and maintaining the cultural heritage.