Study of durability and the physico-mechanical properties of thermally modified wood

(1)

Study of the

physico-Study of the physico-

Study of the

physico-and the durability of thermally

Study of the

physico-and the durability of thermally

_{and the durability of thermally}

and the durability of thermally

NINANE Maxime

1

, HEBERT Jacques

1 Forest and Landscape Management, Gembloux Agro-Bio Tech, University of Liège, B

2 Laboratory of Wood Technology, Department of Natural and Agricultural Environment Studies, Public Service of Wallonia

1. Introduction

Wood is increasingly being used as building material appreciated both as a biological product material appreciated both as a biological product as well as for its carbon fixation properties. However, many methods to preserve wood have However, many methods to preserve wood have negative environmental effects and the use of tropical timber may lead to overexploitation of forests and biodiversity loss. Thermal treatment, by forests and biodiversity loss. Thermal treatment, by hemicelluloses degradation, improves the biological durability and the dimensional stability of wood. This study aims to determine the changes of wood. This study aims to determine the changes in physico-mechanical properties and durability of thermally modified wood.

2. Methodology

thermally modified wood.

2. Methodology

We studied five species (oak, ash, natural beech and We studied five species (oak, ash, natural beech and a variant known as steamed beech, poplar, douglas-fir). For each species, 15 treated and 15 un-treated fir). For each species, 15 treated and 15 un-treated associated samples were analized and compared.

3. Results

A. Physical properties

12.0 14.0 8.0 10.0 12.0 E M C ( % ) 4.0 6.0 8.0 E M C ( % ) Steamed 0.0 2.0 4.0

Oak Ash Beech Steamed

beech Poplar Douglas-fir UnTreated 12.2 11.4 11.8 10.7 9.8 11.3 Treated 5.1 5.2 5.1 5.2 4.7 5.4

0.0

Figure 1. Equilibrium Moisture Content (EMC) for each species with and without thermal treatment all conditioned in the same climate

chamber at 65% RH and 25°_C.

B. Mechanical properties

chamber at 65% RH and 25°_C.

B. Mechanical properties

18000 14000 16000 18000 8000 10000 12000 E ( M P a ) 4000 6000 8000 E

beech Poplar Douglas-fir 0

2000

Figure 2. Stiffness (E) for each species with and without thermal

beech

UnTreated 12868 13521 14613 11993 10604 11982 Treated 13587 14342 16272 12698 10177 10904

Figure 2. Stiffness (E) for each species with and without thermal treatment.

-mechanical properties

thermally modified wood

-mechanical properties

thermally modified wood

_{thermally modified wood}

thermally modified wood

, HEBERT Jacques

1

and JOUREZ Benoit

2

of Liège, B-5030 Gembloux

Department of Natural and Agricultural Environment Studies, Public Service of Wallonia, B-5030 Gembloux

100 120 80 100 M P a ) 40 60 σ f (M P a 0 20

beech Poplar Douglas-fir UnTreated 94 108 112 100 69 90

Treated 48 80 77 63 43 46 0

Figure 3. Static bending strenght

(

σ

f

)

for each species with and

without thermal treatment.

Treated 48 80 77 63 43 46

12.0 8.0 10.0 (N m /c m ²) 4.0 6.0 K ( N m /c m ²) 0.0 2.0

beech Poplar Douglas-fir UnTreated 6.0 8.5 9.7 6.2 3.8 4.5

Treated 2.6 3.4 4.3 2.6 1.1 1.4 0.0

Figure 4. Impact Bending Strength (K) for each species with and without thermal treatment.

Treated 2.6 3.4 4.3 2.6 1.1 1.4

C. Durability

Species

Durability Class

UnTreated Treated Oak 3 1 Ash 5 1 Ash 5 1 Beech 5 3 Steamed beech 5 3 Poplar 5 4 Douglas-fir 4 3

Table 1. Durability class for each species with and without thermal treatment.

4. Conclusion

The results show a decrease in the hygroscopicity and an increase in dimensional stability of and an increase in dimensional stability of heat-treated wood in relation to the degradation of hemicelluloses. The durability of thermally modified wood against wood-destroying fungi increases. The wood against wood-destroying fungi increases. The mechanical properties are influenced variously; heat-treated wood is lightly stiffer for some species but above all more brittle.

but above all more brittle.

Thermally treated wood is a credible alternative for some tropical timbers and for timbers treated with some tropical timbers and for timbers treated with unwanted preservatives.