De Windt, Imke

Li, Wanzhao

Van Acker, Joris

Van den Bulcke, Jan

Ghent University Academic Bibliography

Time of Wetness (ToW) simulation based on testing moisture dynamics of wood Joris Van Acker, Imke De Windt, Wanzhao Li, Jan Van den Bulcke Ghent University (UGent), Laboratory of Wood Technology (Woodlab), Coupure links 653, 9000 Ghent – Belgium, e-mail: joris.vanacker@ugent.be – imke.dewindt@ugent.be – wanzhao.li@ugent.be – jan.vandenbulcke@ugent.be  Keywords: time of wetness, moisture dynamics, wood species, wood based panels, modified wood  Within the framework of CEN/TC 38 (European Committee for Standardization / Durability of wood and wood-based products) the WG 28 (Working Group Performance classification) have been established to harmonize, especially for use class 3 applications, views on durability aspects of wood species, preservative treated and modified wood. The related EU project PerformWood established the concept that natural durability and/or enhanced durability is not solely based on the presence of active ingredients having an impact on both fungi and insects. The material resistance complementary to this is also based on the time of wetness factor. Based on earlier results for plywood experiments were set up for solid wood. For plywood a simulation of time of wetness measured by continuous moisture measurements (CMM – Figure 1) (Van den Bulcke et al. 2009, 2011) was possible by using a floating test including wetting and drying components. For solid wood a soaking/submersion test procedure was added as a second test to distinguish between optimal design of a commodity and design including water trap. These methods have been used in a round robin and results were presented earlier by Brischke et al. (2014). To complement this work some 52 wood species, 17 sets of modified wood and 8 wood based panels were assessed according this protocol soon to become a European standard test method. The method is based on one hand floating specimens with a face on water with edges sealed and on the other hand a submersion test with open end grain cross sections (Figure 2). The dimensions are aligned with common field test specimens. Results showed that absorption and desorption figures after 24 hours could differentiate wood species and still allowed to classify similar material in the same class. Based on curve fitting this approach can seemingly be improved and also parameters that explain better the water uptake rate and release rates next to total absorption and residual moisture content can be included. Data are presented using the unit g/m² for the floating test and kg/m³ for the submersion test but these values can easily be translated in percentages moisture content. The results as earlier presented by Van Acker et al. (2014) are now being compared with continuous moisture measurements to underpin the meaning of the critical parameters in relation to actual time of wetness.  Figure 1: Continuous Moisture Measurement (CMM) set up at UGent – Woodlab  Figure 2: Floating test (left) and submersion test (right)  References Brischke, C., Meyer, L., Hesse, C., Van Acker, J., De Windt, I., Van den Bulcke, J., Conti, E., Humar, M., Viitanen, H., Kutnik, M., Malassenet, L. (2014). Moisture dynamics of wood and wood-based products – Results from an inter-laboratory test. Proceedings 45th IRG Annual Meeting St George, Utah, USA. Document IRG/WP14-20539, 20p.  Van Acker, J., De Windt, I., Li, W., Van den Bulcke, J. (2014). Critical parameters on moisture dynamics in relation to time of wetness as factor in service life prediction. Proceedings 45th IRG Annual Meeting St George, Utah, USA. Document IRG/WP14-20555, 22p. Van den Bulcke, J., Van Acker, J., De Smet. J. (2009). An experimental set-up for real-time continuous moisture measurements of plywood exposed to outdoor climate. Building and Environment, 44, 12: 2368-2377. Van den Bulcke, J., De Windt, I., Defoirdt, N., De Smet, J., Van Acker, J. (2011). Moisture dynamics and fungal susceptibility of plywood. International Biodeterioration & Biodegradation, 65, 5: 708-716.   Acknowledgments: The authors gratefully acknowledge the support of the European Commission through the 7th Framework programme for funding the project PerformWOOD (Coordination and support actions - Grant number 319132). Work programme topics addressed: NMP.2012.4.0-1 Support for standardisation needs to consolidate the technical background for standardisation to deliver new documents on the service life performance of wood in constructions. On a national level support for this work was received from the project DO-IT HOUTBOUW: Sustainable innovation in the field of technology and comfort of living for wood construction applications based on funding from IWT (Flemish agency for Innovation by Science and Technology) – VIS Traject 110803 with CTIB-TCHN (Belgian Institute for Wood Technology). 

Time of Wetness (ToW) simulation based on testing moisture dynamics of wood

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Time of Wetness (ToW) simulation based on testing moisture dynamics of wood

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