1 Introduction
2 Classification of woods
2.1 Different hardwoods
Hardwoods properties | Beech | Hornbeam | Turkey oak | Poplars |
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Names | Hungarian: bükk Scientific name: Fagus sylvatica English: Beech, German: Buche, French: hetre | Hungarian: gyertyán Scientific name: Carpinus betulus English: hornbeam, ironwood, German: Hainbuche, Weißbuche French name: Charme | Hungarian: csertölgy Scientific name: Quercus cerris English: Turkey oak, German: Zerreiche, French: chene chevelu | Hungarian: fehérnyár, rezgőnyár, feketenyár Scientific name: Populus spp. English: White poplar, Aspen, Black poplar |
Morphological characteristics | Trunk shape is 35 to 40 m in height, bole length: 15 to 20 m. Breast height diameter: 0.4 to 0.7 m Branches are thinner Bark is 1 to 2 cm thin and ash-grey in color | 20 to 25 m height, breast height diameter: 50 to 60 cm Branches are thinner Bark is 1 to 2 cm and dark grey in color Life span is 120 to 150 years but needed 60 to 80 years for harvesting | 25 to 30 m height, trunk length: 12 to 15 m. Diameter: 0.3 to 0.5 m Straight and cylindrical trunks. Coarser bark, greyish bark, Bark is 1 to 10 cm | White poplar: 20 to 30 m height, trunk length: 12 to 15 m. Diameter: 0.5 to 1.0 m Smooth bark, greyish |
Defects and limitations | Red heart disease, red beech infection by fungimoustach-like lines, suffocation caused by fungi | Prone to attack by some fungi like Trametes, Serpula | Three basic defects: red heart, frost ribs, and ring shakes | Knots, frost cracks, red heart, prone to biotic attack |
Durability | Varies depending on various condition: 2–5 years: soil contact, 10 to 40 years: outdoor condition, 30–120 years: under water, 200–700 years: permanent dry condition | Varies depending on various condition: 35 years: outdoor condition, ~ 500 years: under water, ~ 800 years: indoors | Varies depending on various condition: 2–5 years: soil contact, 5 to 30 years: outdoor condition, 5–50 years: under water, 50–400 years: permanent dry condition |
Hardwoods properties | Beech | Hornbeam | Turkey oak | Poplars |
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Physical properties | ||||
Density (oven dry) | 490 to 880 kg/m3 | 500 to 820 kg/m3 | 570 to 850 kg/m3 | White p.: 450 kg/m3, Aspen: 490 kg/m3, Black p.: 450 kg/m3, |
Porosity | 55% | 48% | ||
Shrinkage | ||||
Tangential | 11.8% | 11.5% | 8.5 to 9.8% | 5.9 to 8.6% |
Radial | 5.8% | 5.2 to 6.8% | 4.4 to 4.9% | 3.1 to 5.3% |
Longitudinal | 0.3% | 0.5% | 0.3 to 0.4% | 0.2 to 0.4% |
Volumetric | 14.0 to 21.0% | 18.8% | 12.9 to 14.6% | 9.5 to 14.7% |
Mechanical properties | (white poplar) | |||
Tensile strength | 57 to 180 MPa | 47 to 200 MPa, | 100 to 139 MPa | 82.3 MPa |
Bending strength | 74 to 210 MPa | 58 to 200 MPa | 94 to 136 MPa | 67.5 MPa |
Comp. strength | 41 to 99 MPa | 54 to 99 MPa | 44 to 71.3 MPa | 38.3 MPa |
Impact strength | 3 to 19 J/cm2 | 8 to 12 J/cm2 | 10 J/cm2 | 4 to 5 J/cm2 |
Hardness (Brinell) | 72 MPa (end grain) 34 MPa (side grain) | 71 MPa (end grain) 29 to 36 MPa (side grain) | 57 MPa (end grain) | 27 MPa (end grain) |
Chemical properties | ||||
Cellulose | 45.4% | 43% | 42–47% | 45 to 52.4% |
Hemicellulose | 32 to 34.5% | 20–27% | ||
Pentosans | 17.8%, | 17.8%, | ||
Hexosans | 4.4% | |||
Lignin | 22.7% | 19.3 to 22.5% | 25 to 27% | 23.2 to 25.2% |
Ash | 1.6% | 0.5% | Others: 3–4% | 0.41 to 0.89% |
Extractives: (benzene-alcohol extraction) | 0.7% | 2.4% | 2.3 to 3.2% | |
pH value | 5.1 to 5.4 | 5.2 | 4.9 | 5.8 |
2.1.1 Turkey oak
2.1.2 Hornbeam
2.1.3 Beech
2.1.4 Domestic poplar (Populus spp.)
3 LSL as an engineered wood product
4 Fabrication of LSL with specification
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Firstly, log conditioning is carried out to prepare the logs for further processing. This may include debarking and removing any defects or irregularities from the logs.
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The next step is the stranding process, where the logs are transformed into small strands. This is typically done by mechanically cutting or shredding the logs into thin, elongated pieces. These strands are then dried to reduce their moisture content, ensuring dimensional stability and preventing mold or decay during the subsequent stages.
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Once the strands are dried, they go through a blending process. In this step, the strands from different log batches or wood species are combined to achieve a desired blend and ensure consistent material properties throughout the LSL panel.
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The blended strands are then formed into a mat or layer, where they are oriented in a specific arrangement to optimize the mechanical properties of the final LSL product. This mat is then subjected to high pressure and temperature during the pressing stage. The application of heat and pressure activates the resin binder, which bonds the strands together and forms a solid, cohesive LSL.
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After pressing, the LSL shall undergo final processing, which may include trimming, sanding, and cutting to the desired dimensions and specifications.
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Overall, the LSL production process encompasses log conditioning, stranding, drying, blending, forming, pressing, and final processing stages, each playing a crucial role in transforming raw materials into high-quality LSL products suitable for various construction applications.
5 Properties of LSL products
5.1 Mechanical properties
Wood species | Tensile Properties | Flexural Properties | Physical Properties | References |
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Aspen (Populus tremuloides) | Tensile strength: 45.11 MPa | MOR: 48.19 MPa MOE:11.609 GPa | Wang et al. (2015) | |
Aspen (Populus tremuloides) (control sample) | Density: 657 (42.61) kg/m3 MOR: 11.858 MPa MOE: 47.48 GPa | MC: 8.9 (0.6) % Swelling: 1.05 to 1.2% | Denizli (1997) | |
Paulownia (control) | Shear strength: 10.34 MPa IBS: 0.84 MPa | Density: 88.85 kg/m3 MOR: 88.85 MPa MOE: 10.763 GPa | Bayatkashkoli and Faegh (2014) | |
Mixed hardwood | Maximum tensile strength: 35.8 (5.47) MPa | MOE:11.1 (1.19) GPa | MC: 6.8% | Aro et al. (2017) |
5.2 Chemical properties
5.3 Physical properties
5.4 Thermal properties
5.5 Durability
5.6 Fire resistance
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The flame spread rating pertains to the velocity at which flames propagate across the exterior of a substance. LSL generally exhibits a low flame spread rating, which implies a comparatively less inclination to facilitate the propagation of flames.
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The charring rate refers to the phenomenon observed when wood is subjected to fire, resulting in the formation of a protective layer of charred wood. The fire resistance of LSL is enhanced by its characteristic of displaying a consistent and uniform rate of charring.
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The maintenance of structural integrity during a fire is seen as a notable benefit of LSL. Although LSL may undergo charring, it generally maintains a substantial proportion of its load-bearing capability, hence offering ongoing structural support even when subjected to fire.
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Fire retardant treatments have the potential to augment the fire resistance of LSL. These treatments have the potential to mitigate the flammability of wood and impede the pace of fire propagation, hence offering supplementary fire safety measures.
5.7 Sustainability
6 Application potential of LSL
7 Economical aspects
8 SWOT analysis
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Because of its durability and consistency, LSL may be used in many building contexts.
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Since LSL may be crafted from many different kinds of wood, it can be engineered for various applications.
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In comparison to solid timber, LSL is more affordable.
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Because of its high tensile strength and dimensional stability, LSL may be used in a variety of structural contexts.
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The appearance of LSL may be viewed unfavourable by some, and restrict its usage in places where solid wood timber would be preferred.
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If terms of flame resistance, LSL has the same issues as solid wood and other wood based products.
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Because of its increased density, LSL may be more challenging to process and transport than solid timber lumber.
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Because it makes use of widely accessible wood species, LSL may help promote responsible forest management.
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Improved mechanical qualities and a wider array of potential uses may result from further investigation into and development of LSL processing techniques.
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The rising need for eco-friendly building supplies presents an opportunity for LSL.
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Recent raw material shortages and supply chain issues created an increased need for construction materials and more openness to innovative solutions.
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In certain areas, the number of tree species suited for LSL production may be low.
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The demand for LSL may fall if more viable substitutes are developed.
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In certain cases, the usage of LSL might be hindered by revisions to legislation or building requirements.