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Blom, Åsa
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Publications (10 of 30) Show all publications
Sjökvist, T., Niklewski, J. & Blom, Å. (2019). Effect of wood density and cracks on the moisture content of coated Norway spruce (Picea abies (L.) Karst.). Wood and Fiber Science, 51(2), 160-172
Open this publication in new window or tab >>Effect of wood density and cracks on the moisture content of coated Norway spruce (Picea abies (L.) Karst.)
2019 (English)In: Wood and Fiber Science, ISSN 0735-6161, Vol. 51, no 2, p. 160-172Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Society of Wood Science and Technology, USA, 2019
National Category
Wood Science Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-81577 (URN)10.22382/wfs-2019-017 (DOI)
Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-08-28Bibliographically approved
Sjökvist, T. & Blom, Å. (2019). The influence of coating color, heartwood and sapwood, on moisture content and growth of microorganisms on the surface during outdoor exposure of Norway spruce boards. Journal of Coatings Technology and Research, 16(3), 819-826
Open this publication in new window or tab >>The influence of coating color, heartwood and sapwood, on moisture content and growth of microorganisms on the surface during outdoor exposure of Norway spruce boards
2019 (English)In: Journal of Coatings Technology and Research, ISSN 1547-0091, Vol. 16, no 3, p. 819-826Article in journal (Refereed) Published
Abstract [en]

The use of wood contributes to the global transformation into a bio-based community. There are, however, challenges. The growth of mold, rot fungi, and algae on the coated surface is of major concern due to decreased aesthetic service life and shorter maintenance intervals. The colonization of a coated surface requires the presence of spores, nutrients, and a sufficient amount of water. This work studied the influence of using heartwood and sapwood on the moisture content (MC) and growth of microorganisms on the surface of coated Norway spruce boards [Picea abies (L.) Karst.]. The results revealed a relationship of heartwood samples having a lower MC and a lower or equal degree of biological growth on the coated surface than sapwood samples. The relationship was valid through a range of densities (309–548 kg/m3) and two different coating systems based on either an alkyd or an acrylic resin. Furthermore, the choice of coating color (red compared to white) affected the MC as the red-colored samples had a lower MC, combined with no growth of microorganisms.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Mold Fungi Algae Durability Cladding
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-79712 (URN)10.1007/s11998-018-00165-3 (DOI)000466347800017 ()2-s2.0-85060156167 (Scopus ID)
Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-08-29Bibliographically approved
Sjökvist, T., Wålinder, M. E. .. & Blom, Å. (2018). Liquid sorption characterisation of Norway spruce heartwood and sapwood using a muiticycle Wilhelmy plate metho. International Wood Products Journal, 9(2), 58-65
Open this publication in new window or tab >>Liquid sorption characterisation of Norway spruce heartwood and sapwood using a muiticycle Wilhelmy plate metho
2018 (English)In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 9, no 2, p. 58-65Article in journal (Refereed) Published
Abstract [en]

A multicycle Wilhelmy plate method was applied to study the water and octane sorption behaviour of small Norway spruce veneers. Dry heart- and sapwood samples of varying density were investigated. The results showed a correlation between the porosity and the sorption of octane for all samples, i.e. a higher wood porosity resulted in higher octane sorption. However, no difference in octane sorption was found between heart- and sapwood samples of similar density. The water sorption behaviour was difficult to interpret, probably due to the influence of surface-active wood extractives. It is suggested that the presence of such extractives, particularly in the sapwood samples, increases the sorption of water due to a significant decrease in its apparent surface tension. Hence, the results indicate that the liquid water sorption of spruce heart- and sapwood is strongly influenced by variations in the extractives content rather than by the micromorphology.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
Keywords
Picea abies, water, octane, extractives, permeability, pit aspiration, coating, durability
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-73984 (URN)10.1080/20426445.2018.1467602 (DOI)000440888400004 ()2-s2.0-85046402339 (Scopus ID)
Funder
Swedish Research Council Formas, EnWoBio 2014-172
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2019-08-29Bibliographically approved
Ahmed, S. A., Morén, T., Sehlstedt-Persson, M. & Blom, Å. (2017). Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally-modified European aspen and downy birch wood. Journal of Wood Science, 63(1), 74-82
Open this publication in new window or tab >>Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally-modified European aspen and downy birch wood
2017 (English)In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 63, no 1, p. 74-82Article in journal (Refereed) Published
Abstract [en]

Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study was to investigate if these properties enhanced in thermally modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood, especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth, whereas a significant anti-mold effect was observed on Beckers oil treated samples.

Place, publisher, year, edition, pages
Japan: Springer-Verlag Tokyo Inc., 2017
Keywords
Thermal modification, oil impregnation, dimensional stability, durability, mold
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-57073 (URN)10.1007/s10086-016-1595-y (DOI)000394991100008 ()2-s2.0-84996656545 (Scopus ID)
Available from: 2016-11-28 Created: 2016-10-05 Last updated: 2019-08-29Bibliographically approved
Sjökvist, T. & Blom, Å. (2017). Utomhusexponering av ytbehandlat trä: Undersökning av trämaterialets påverkan på beständigheten hos en målad granpanel. Växjö: Linnéuniversitetet
Open this publication in new window or tab >>Utomhusexponering av ytbehandlat trä: Undersökning av trämaterialets påverkan på beständigheten hos en målad granpanel
2017 (Swedish)Report (Other (popular science, discussion, etc.))
Place, publisher, year, edition, pages
Växjö: Linnéuniversitetet, 2017. p. 46
Series
Rapporter: Fakulteten för teknik, Linnéuniversitetet ; 50
Keywords
Gran, Målad panel, Utomhus, Beständighet, Linolja, Alkyd, Akrylat, Slamfärg
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-71485 (URN)978-91-88357-97-7 (ISBN)
Available from: 2018-03-12 Created: 2018-03-12 Last updated: 2018-03-15Bibliographically approved
Blom, Å., Johansson, J., Schauerte, T. & Thörnqvist, T. (2017). Utomhuskonstruktioner i trä: några erfarenheter från byggnation i trä av flerbostadshus. Linnéuniversitetet
Open this publication in new window or tab >>Utomhuskonstruktioner i trä: några erfarenheter från byggnation i trä av flerbostadshus
2017 (Swedish)Other (Other academic)
Abstract [sv]

Användandet av materialet trä i produkter är ett lån från naturen som förr eller senare genom nedbrytning av vedsubstansen ska återföras till det naturliga kretsloppet. Avseende användningen av solitt trä i produkter bestäms tidsperioden innan återföringen till naturen av produktens konstruktion och trämaterialet i sig självt i relation till den omgivande miljön samt användningen och hanteringen av produkten. En produkts förmåga att motstå, eller behålla sina egenskaper trots dessa yttre påfrestningar benämns dess beständighet.

Place, publisher, year, pages
Linnéuniversitetet, 2017. p. 33
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-72253 (URN)978-91-88357-93-9 (ISBN)
Available from: 2018-04-05 Created: 2018-04-05 Last updated: 2019-09-13Bibliographically approved
Sjökvist, T. & Blom, Å. (2016). Influence of some wood characteristics on the variation of moisture content in outdoor exposed coated Norway spruce panels. In: : . Paper presented at 70th International convention Portland, Oregon, USA, June 27-29, 2016. Forest Products Society
Open this publication in new window or tab >>Influence of some wood characteristics on the variation of moisture content in outdoor exposed coated Norway spruce panels
2016 (English)Conference paper, Published paper (Other academic)
Abstract [en]

A field test of coated spruce was exposed outdoors during three years, measuring the influence of wood characteristics on the variation of moisture content in coated panels. Wood samples had following characteristics: fast-grown or slow-grown wood, heartwood or sapwood. Three different film-forming coatings were tested and all samples were exposed above ground on racks. The measured moisture contents were evaluated using the statistical method Principal Component Analysis (PCA). The moisture content of the coated samples was clearly influenced by wood characteristics; fast-grown wood had higher moisture content and higher moisture fluctuation than slow-grown wood in each respective coating system. The choice of coating system also affects the wood moisture content. The result indicates that in order to achieve low moisture content- excluding the effectiveness of coatings, wood characteristics should also be considered.

Place, publisher, year, edition, pages
Forest Products Society, 2016
Keywords
Exterior coating, Moisture content, Heartwood, Sapwood, Fast-grown, Slow-grown, Alkyd, Acrylate
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-56684 (URN)
Conference
70th International convention Portland, Oregon, USA, June 27-29, 2016
Projects
The Bridge
Available from: 2016-09-23 Created: 2016-09-23 Last updated: 2017-01-17Bibliographically approved
Sjökvist, T. & Blom, Å. (2016). The impact of heartwood and sapwood on biological discoloration of a painted surface. In: Bruno Andersons, Arnis Kokorevics (Ed.), Proceedings of the 12th meeting of the Northern European Network for Wood Science and Engineering (WSE): Wood science and engineering - a key factor on the transition to Bioeconomy. September 12-13, 2016, Riga, Latvia. Paper presented at 12th Northern European Network for Wood Science and Engineering (WSE) ,Riga, Latvia, 12-13 September, 2016 (pp. 137-142). Riga: Latvian State Institute of Wood Chemistry
Open this publication in new window or tab >>The impact of heartwood and sapwood on biological discoloration of a painted surface
2016 (English)In: Proceedings of the 12th meeting of the Northern European Network for Wood Science and Engineering (WSE): Wood science and engineering - a key factor on the transition to Bioeconomy. September 12-13, 2016, Riga, Latvia / [ed] Bruno Andersons, Arnis Kokorevics, Riga: Latvian State Institute of Wood Chemistry , 2016, p. 137-142Conference paper, Published paper (Other academic)
Abstract [en]

Wood material has advantages, it comes from a renewable source and it is easy to manage. But one disadvantage when used outdoors is biological discoloration of the material. Some impact on the discoloration is the presence of moisture and nutrients, necessary components for the microorganisms to grow and start a colonisation. Samples made of Norway spruce (Picea abies (L.) Karst) heartwood or sapwood coated with two different film forming paints was studied. The paints had a binder formula made of alkyd or acrylate. Additional parameters related to study the influence of moisture content on discoloration were high and low density material, with and without impregnation oil. Outdoor exposure was made during five years in the southern part of Sweden. The samples were hung with 45 degree inclination, facing south direction. Visual differences in biological surface discoloration were observed for samples within the same paint, which could be explained by differences in heartwood and sapwood.

Place, publisher, year, edition, pages
Riga: Latvian State Institute of Wood Chemistry, 2016
Keywords
Discoloration, Heartwood, Sapwood, Paint
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-56687 (URN)978-9934-14-981-8 (ISBN)978-9934-14-982-5 (ISBN)
Conference
12th Northern European Network for Wood Science and Engineering (WSE) ,Riga, Latvia, 12-13 September, 2016
Available from: 2016-09-23 Created: 2016-09-23 Last updated: 2017-04-13Bibliographically approved
Johansson, M., Mahapatra, K., Vessby, J., Blom, Å. & Olsson, A. (2014). Expert competence for sustainable timber engineering: a master program in close cooperation between industry and academia. In: WCTE 2014 - World Conference on Timber Engineering, Proceedings: . Paper presented at World conference on timber engineering, 11-14 August, 2014, Quebec.
Open this publication in new window or tab >>Expert competence for sustainable timber engineering: a master program in close cooperation between industry and academia
Show others...
2014 (English)In: WCTE 2014 - World Conference on Timber Engineering, Proceedings, 2014Conference paper, Published paper (Refereed)
Abstract [en]

From a legislative point of view it has been possible to build timber buildings with arbitrary number of storeys in Sweden during almost two decades. Several buildings up to eight storeys have been completed during that time, but the competence for planning and building such structures are limited to a handful of actors. This fact has been recognized by funders of research/education and an educational program for spreading the knowledge within the industry led by Linnaeus University is financed since about two years. Particularly interesting in the programme is that the courses are developed in cooperation between the industry and the academia. The courses are to fulfil needs with respect to knowledge, but also with respect to format so that the main target group, skilled engineers within the industry, can find the motivation to follow a course or lager parts of the program.

Keywords
Education, timber building, courses, interaction
National Category
Other Civil Engineering
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-34458 (URN)2-s2.0-85067717610 (Scopus ID)
Conference
World conference on timber engineering, 11-14 August, 2014, Quebec
Available from: 2014-05-28 Created: 2014-05-28 Last updated: 2019-08-27Bibliographically approved
Blom, Å. & Thörnqvist, T. (2014). Live storage and drying of storm-felled Norwayspruce (Picea abies, L. Karst.) and Scots pine (Pinussylvestris L.) trees. Wood Material Science & Engineering, 9(4), 209-213
Open this publication in new window or tab >>Live storage and drying of storm-felled Norwayspruce (Picea abies, L. Karst.) and Scots pine (Pinussylvestris L.) trees
2014 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, no 4, p. 209-213Article in journal (Refereed) Published
Abstract [en]

Storm-felled trees left in the forest for a shorter or longer period, affect the quality of the logs. The change in quality ismainly because of attack of fungi and insects, which in turn depends on the moisture content (MC) of the sapwood. Thepurpose of this study was to receive more knowledge about drying of storm-felled trees by investigating how fast winterstorm-felled Norway spruce and Scots pine dried when left in the forest. Sixteen storm-felled spruces with part of the rootsstill in ground contact were selected from three stands and in addition to 10 pines from one of the stands. The trees wereexamined for MC in the sapwood until 21 months after the storm. This study indicates that wind-thrown trees with rootsstill connected to the soil can survive one summer without any value loss caused by draught, fungi and insects. The standconditions can be of importance as the storm-felled trees in the stand, with scattered windthrow, were in best condition afterone year, as they were shadowed by the trees still standing. Comparing spruces and pines with the stand with scatteredwindthrow, pines were more sensitive to drought and reached critical MC earlier.

National Category
Materials Engineering
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-19006 (URN)10.1080/17480272.2014.881914 (DOI)2-s2.0-84911384320 (Scopus ID)
Available from: 2012-05-29 Created: 2012-05-29 Last updated: 2017-12-07Bibliographically approved
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