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Use of thermally modified wood in building constructions
Prof.dr. Franc [email protected]
University of LjubljanaBiotechnical Faculty,Department of Wood
Science and Technology,Rona dolina, Cesta VIII/34SI1000 Ljubljana,
Slovenia
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INTRODUCTIONDifferent wood modification
process:ThermalChemicalEnzimatic
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INTRODUCTIONDIFFERENT HEATING MEDIA: nitrogen, steam, oil VACUUM
A SLOVENIAN METHODExposure to high temperatures cause severe
degradation of cellulose and losses in mechanical properties
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INTRODUCTIONTemperatures from 160 C to 260 CAbsence of
oxygenProcess of wood modificationChemical changes in wood cell
wallsChanges of wood (=modified wood)
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MATERIALS AND METHODS - modificationSOFTWOOD or HARDWOOD
Phases of process (24 h)
drying at 103 Cvacuuming up to 0,05 barheating to 150 Cheating
to T of modif. (3 h)cooling down
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PROPERTIES OF THERMALLY MODIFIED WOODImprovement of durability
and dimensional stabilityRemoving of resinsImprovement of resonant
(acoustic) propertiesMass lossChange of physical
properties:ColourReduction of strength and stiffnessBending
strength 10 % 50 %
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Results - change of colour
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SBH
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Elm wood
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MASS LOSSESSpruce:3 % (190 C) 24 % (230 C) Larch:5 % (190 C) 31
% (230 C)
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MATERIALS AND METHODS decay testsDECAY TESTSmini-block test
(Bravery)
cross-section: 10 mm 5 mmlength: 30 mmGloeophyllum trabeum
Coniophora puteana exposure: 8 weeks
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DECAY samples treated at 200 CRESULTS decay tests
Mass loss
(%)GtCpSpruceuntreated35,25,45612treated1,51,18,94,4Larchuntreated34,27,729,02,9treated1,170,180,900,21
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MATERIALS AND METHODS dimensional stabilityDIMENSIONAL
STABILITYASE soaking/ovendrying test (3 cycles)
shrinkage () in r, t dim.
20 mm 20 mm 20 mm
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50 mm 20 mm 20 mmunoriented ABSORPTION OF WATER VAPOUR AT 83 %
AIR HUMIDITY AND T = 25 C
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Exposure at 83 % RH and 25 C
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RESULTS: absorption of water vapour spruce wood
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RESULTS: absorption of water vapour beech wood
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RESULTS: absorption of water vapour oak wood
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DIMENSIONAL STABILITY (spruce)
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DIMENSIONAL STABILITY (beech)
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DIMENSIONAL STABILITY (oak)
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APPROXIMATION OF REDUCTION OF DIMENSIONS OF MODIFIED WOOD
SPECIMENS (spruce)
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APPROXIMATION OF REDUCTION OF DIMENSIONS OF MODIFIED WOOD
SPECIMENS (beech)
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APPROXIMATION OF REDUCTION OF DIMENSIONS OF MODIFIED WOOD
SPECIMENS (oak)
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MATERIALS AND METHODS MOE AND MORMOE, MOR static three-point
bending testZwick Z-100
300 mm 20 mm x 20 mm, absolute dry
10 mm/min
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MATERIALS AND METHODS - MOEMOE non-destructivelynatural
vibration analysis in clamped-free conditions
300 mm 20 mm 10 mm, absolute dry
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MATERIALS AND METHODS - MOEMOE non-destructivelyinductive
proximity sensor FFTndynamic signal analyzer
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MOR AND MOE of absolute dry samplesRESULTS MOE and MOR
Grafikon1
9430733095504442111582480568.5568.5556.5556.5774774962962261.5261.5774774
8804872193417504109275331622.5622.5431.5431.5871.5871.5688.5688.5332.5332.5871.5871.5
107921041197337712100845487372.5372.5862862418.5418.5324.5324.5715.5715.5418.5418.5
13342130431308010636MOE (larch-vibration)MOE
(larch-vibration)231231607.5607.5267.5267.5555.5555.5
Untreated
Treated, 190 C
Untreated
Treated, 210 C
Untreated
Treated, 230 C
MPa
List1
9430568.51,137100 x MOR (spruce-bending)
7,3309621,924
9,5505571,113
4,442262523
11,1589751,949
2,4807741,548
8,8046231,245MOE (spruce-bending)
8,7216891,377
9,341432863
7,504333665
10,9279301,859
5,3318721,743
10,792373745MOE (spruce-vibration)
10,411325649
9,7338621,724
7,7127161,431
10,0847111,422
5,487419837
13,342231462MOE (larch-vibration)
13,043268535
13,0806081,215
10,6365561,111
List1
000000568.5568.5556.5556.5774774962962261.5261.5774774
000000622.5622.5431.5431.5871.5871.5688.5688.5332.5332.5871.5871.5
000000372.5372.5862862418.5418.5324.5324.5715.5715.5418.5418.5
0000231231607.5607.5267.5267.5555.5555.5
Untreated
Treated, 190 C
Untreated
Treated, 210 C
Untreated
Treated, 230 C
MPa
List2
List3
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Laboratory chamber for thermal wood modification
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Industrial chamber for thermal wood modification
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Silvaprodukt d.o.o., Ljubljana, Sovenia
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The first product made from thermally modified wood, modified
according to our procedure
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CONCLUSIONSThe best characteristics of the products made of
modified wood were achieved with wood, modified at temperatures
between 180C and 210 CIn spite of the treatment, the mechanical
properties of modified wood are still appropriate for wood to be
used in constructionsWood modification process can ensure
appropriate resistance for diverse ways of utilisation of wooden
products, especially in in wet conditions
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