| 1. |
- Niklewski, J., et al.
(författare)
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Moisture behavior of weathered wood surfaces during cyclic wetting : measurements and modeling
- 2018
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Ingår i: Wood Science and Technology. - : Springer Science and Business Media LLC. - 0043-7719 .- 1432-5225. ; 52:6, s. 1431-1450
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Tidskriftsartikel (refereegranskat)abstract
- The effects of weathering on the in-service moisture behavior of wood have received only limited attention so far, with much focus being on the effect of photodegradation on the hydrophobicity of the wood surface. The objective of the present study was to examine the effect of weathering surfaces on the overall moisture behavior of wood specimens exposed to short-term cyclic spraying, with special emphasis on the surface conditions involved. Specimens cut from eight different species including hardwoods and softwoods were weathered for 8 years and continuously monitored during a single-sided cyclic spraying together with a set of axially matched controls. After each spray cycle, the duration of surface wetness was evaluated by resistance moisture sensors as well as an optical approach (colorimetric) based on time-lapse images. The moisture content in the core was monitored simultaneously by use of resistance moisture sensors. The optical method correlated well with the electrical resistance measurements and provided a simple and practical measure of the areal distribution of the surface wetness. The results showed specimens with a weathered surface to sustain a wet surface for about twice the duration of their axially matched control. A considerable, albeit smaller, effect was also observed deeper in the core. By adapting the length of the wet period on the exposed boundary, the corresponding response at the core of the Norway spruce specimens was reproduced numerically.
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| 2. |
- Shahreza, S.k., et al.
(författare)
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Making decision on repointing of clay brick facades on the basis of moisture content and water absorption tests results – a review of assessment methods
- 2020
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Ingår i: Brick and Block Masonry - From Historical to Sustainable Masonry : Proceedings of the 17th International Brick/Block Masonry Conference (17thIB2MaC 2020), July 5-8, 2020, Kraków, Poland - Proceedings of the 17th International Brick/Block Masonry Conference (17thIB2MaC 2020), July 5-8, 2020, Kraków, Poland. - : CRC Press. - 9781003098508 ; , s. 617-623
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Konferensbidrag (refereegranskat)abstract
- Use of clay brick masonry in façades is often motivated by its aesthetic values and durability. Yet, mortar joints exposed to climate agents erode over time, expected to cause elevated moisture content and water absorption. Thus, it is often recommended that 40- to 50-year-old facades should be repointed – a measure which is intrusive and costly. Decision is in many cases taken without a clear evidence that repointing will diminish water absorption and moisture content in the renovated walls. This paper presents the results of a state-of-the-art study on field and laboratory methods to measure moisture content and water absorption in clay brick masonry. For common buildings, use of low cost and time efficient measurement methods is feasible. However, prior to measurements, analysis of technical and climate data combined with a visual inspection might give a rational basis for decision on repointing or other alternative maintenance measures.
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| 3. |
- Sjökvist, Tinh, 1978-, et al.
(författare)
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Effect of wood density and cracks on the moisture content of coated Norway spruce (Picea abies (L.) Karst.)
- 2019
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 51:2, s. 160-172
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Tidskriftsartikel (refereegranskat)abstract
- A protective coating is often used on the cladding of wooden facades to limit the absorption of moisture. Low wood moisture content (MC) is essential to obtain satisfactory durability performance. Wood density is known to influence the water sorption and crack formation of uncoated wood. However, the effect of density on the aforementioned behaviors of coated spruce is not yet fully understood. Six-years of data on the crack formation and the MC variation of outdoor exposed panels are analyzed in this article. The outdoor test was complemented by a subsequent laboratory experiment, wherein the MC variation was monitored at different depths on the board during artificial water spraying. The aim of this research was to increase the knowledge about how wood density and aging affect the water sorption of coated spruce through the crack formation. The results indicated that wood density had an impact on the overall sorption behavior of coated spruce. Low-density spruce contributed to faster water absorption and desorption processes than coated samples with higher density. However, the observed correlation to density was limited to a condition with an intact coating. High-density characteristics contributed to more crack formation, and the density-sorption relationship reversed with a cracked coating. A cracked coating caused a strong local increase in the MC of the wood at the location of the cracks. Weather-exposed replicates without cracks had a higher MC in the core of the board compared with the value beneath the coating. The higher MC is probably due to the water sorption of the uncoated backside of the panel. Such an occurrence raised awareness for future studies to account for multidimensional sorption behavior from all sides of the panel. The local difference in MC also raises awareness for future studies to investigate local MC variations (as opposed to the global average of the panel) in research on the durability of coated wood.
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