Wood Deterioration, Protection and Maintenance (eBook)

Ladislav Reinprecht (Autor)

eBook Download: EPUB

2016
Wiley (Verlag)
978-1-119-10651-7 (ISBN)

Infos

Wood Deterioration, Protection and Maintenance provides an up to date discussion of the natural durability of wood, wood degradation processes, and methods of structural and chemical protection of wood. Modern active substances in wood preservatives and the relationships between preservative properties, the anatomical structure and moisture content of wood and protective processes involving pressure and/or diffusion driving forces are fully illustrated.

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WOOD DETERIORATION, PROTECTION AND MAINTENANCE Wood has low embodied energy, is a renewable resource and can perform extremely well in a range of construction applications, so it is not surprising that there is growing interest in the use of wood in new buildings. As a natural material, wood can be subject to degradation by a range of environmental factors, insects, bacteria or fungi. Advances in the understanding of the degradation processes caused by these factors, as well as increased knowledge about boundary environmental conditions and the extractives that suppress the development of timber pests, have led to new methods of structural, physical and chemical protection of wood and wooden composites. The result is that wood can deliver high-performance, long-life buildings and structures with low environmental impact at relatively modest cost. Wood Deterioration, Protection and Maintenance provides an up-to-date discussion of the natural durability of wood, wood degradation processes, and methods of structural, physical and chemical protection of wood. The important information relating to wood degradation by abiotic and biotic agents in the context of the basic structure of wood is fully discussed, showing how structural changes in damaged wood relate to physical and mechanical properties. Modern active substances in wood protection and the relationships between preservative properties, the anatomical structure and moisture content of wood, and protective processes involving pressure and/or diffusion driving forces are fully illustrated. Mentioned also are principles of wood maintenance, together with modes of damaged wood identification, sterilization and reconstruction. OTHER BOOKS OF INTEREST Wood Modification: Chemical, Thermal and Other Processes Callum A. S. Hill Hardback ISBN 9780470021729 January 2006, Wiley Wood in Construction: How to Avoid Costly Mistakes Jim Coulson Paperback ISBN 9780470657775 March 2012, Wiley Blackwell Structural Timber Design to Eurocode 5, 2nd Edition Jack Porteous, Abdy Kermani Paperback ISBN 9780470675007 May 2013, Wiley Blackwell

Autor

THE AUTHOR Prof. Ing. Ladislav Reinprecht is a wood protection specialist at the Faculty of Wood Sciences and Technology, Technical University of Zvolen, Slovak Republic. He holds an MSc in Organic Chemistry from the Slovak Technical University in Bratislava and a PhD in Wood Technology from the Technical University of Zvolen.

Textauszug

1
Wood Durability and Lifetime of Wooden Products

Wooden products (furniture, flooring, doors, etc.) and constructions (log cabins, bridges, ceilings, trusses, etc.) produced from various species of wood and types of wooden composites are in practice exposed to different environments, where they can be subjected to more forms of degradation (see Chapters 2 and 3).

With the aim to suppress the degradation processes in the wood, and also in glues, paints and other materials used for wooden products and constructions, it is desirable to use suitable forms of their structural, chemical and modifying protection so that their lifetime can be suitably increased (see Chapters 4, 5 and 6).

The service life of wooden products and constructions can be increased by their regular maintenance. However, when degradation processes in wood and/or in additional materials occur and cause damage, appropriate restoration methods should be used (see Chapter 7).

1.1 Basic information about wood structure and its properties

The structure of wood and wooden composites (Figures 1.1 and 1.2) and their exposure in conditions suitable for the action of abiotic factors and/or the activity of biological pests (Figure 1.3) are the basic prerequisites for potential damage of wooden products and constructions.

Figure 1.1 Structural levels of wood (modified from Eriksson et al. (1990) and Reinprecht (2008))

Source: Eriksson, K-E., Blanchette, R. A. and Ander, P. (1990) Microbial and enzymatic degradation of wood and wood components. Springer Verlag – Berlin Heidelberg, 407 p. Reproduced by permission of Springer

Figure 1.2 The basic types of wooden composites: (1) glulam (glued joints); (2) prefinished wood (coatings or foils); (3) wood–plastic (fibre reinforcement); (4) fibreboard (dispersion systems); (5) particleboard (macro-dispersion systems); (6) plywood (laminated systems); (7) impregnated wood (penetrations or diffusions). (Note: composite is a multicomponent system of materials consisting of at least two macroscopically distinguishable phases, of which at least one is solid)

Figure 1.3 Biological and abiotic wood-degrading factors

Source: R., L. (2013) Wood Protection, Handbook, TU Zvolen, Slovakia, 134 p. Reproduced by permission of TU Zvolen

Wood is a biopolymer, created by a genetically encoded system of photosynthetic and subsequent biochemical reactions in the cambial initials of trees (Figure 1.1). Trees consist of approximately 70–93 vol.% of wood, with the rest being bast, bark and needles or leaves. Wood is the internal, lignified part of the stem, branches and roots. The characteristics of wood include: (1) anisotropy, typical in three anatomical directions – longitudinal, radial and tangential;

(2) inhomogeneity, influenced by the sapwood and heartwood, the early wood and late wood, and so on; (3) specificity, given by the wood species; and (4) variability, given by the growth conditions of the tree of a given wood species.

Wood is a traditional material, used for producing wooden buildings, furniture, work and sport tools, as well as art works. It is currently an irreplaceable raw material for the production of bio-based composites with the targeted combination of wood particles in various stages of disintegration and pretreatment with a complementary system of adhesives, waxes and other additives (Figure 1.2).

1.1.1 Wood structure

The structure of wood (Figure 1.1, Boxes 1.1, 1.2, 1.3 and 1.4) and wooden composites (Figure 1.2) is defined at four levels:

• primary (i.e. molecular/chemical structure);
• secondary (i.e. anatomical/submicroscopic structure);
• tertiary (i.e. morphological/microscopic structure);
• quaternary (i.e. geometric/macroscopic structure).

Box 1.1 A basic preview of the geometric structure of wood

The geometric structure of wood

Defines

The external appearance – shape, volume, colour, the ratio of tangential, radial and facial areas, the proportion of sapwood, heartwood and/or mature wood, the proportion of early and late wood in annual rings, the roughness and overall quality of the surfaces, and so on.

The macroscopic inhomogeneities – knots, compression or tension wood, juvenile wood, false heart, resin chanals, and so on, together with their type, frequency and state of health (e.g. damage by rot).

Depends on

• the morphological structural level (i.e. the proportional and spatial distribution of various types of cell elements in the wood);
• the growth defects and anomalies in the wood;
• the mechanical and other loads/treatments of the wood.

Source: R., L. (2008) Ochrana Dreva (Wood Protection), Handbook, TU Zvolen, Slovakia, 453 p. Reproduced by permission of TU Zvolen.

Box 1.2 A basic preview of the morphological structure of wood

The morphological structure of wood

Defines

The individual cells – type, shape, dimensions, slenderness factor, orientation to the pith (longitudinal, radial), thickness of the cell wall, thinning in the cell wall (type, frequency, location), and so on.

The grouping of cells – proportion and location of parenchymatic, libriform, vessel, tracheid and other cell-types in the wood tissues.

Depends on

The wood species (Fengel & Wegener, 2003; Wagenführ, 2007; Wiedenhoeft, 2010; Wiemann, 2010):

• Wood of coniferous species has a simple and fairly regular morphological structure. Approximately 90–95% of wood volume is formed of early and late tracheids. Tracheids have a conductive and strengthening function. They are 2–5 mm long (late are approximately 10% longer) and 0.015–0.045 mm wide. Their cell walls, with a thickness of 0.002–0.008 mm, contain a fairly high number of pit pairs, usually 60–100 in early tracheids and 5–25 in late tracheids. Pit-pairs with a diameter of 0.008–0.03 mm are mainly at the end of tracheids on their radial walls. Opened pit-pairs provide interconnection between tracheids, which is used in the transport of liquids into the wood at its chemical protection and modification. Parenchymatic, thin-walled cells form stock tissue with living protoplasm. They are located in radially oriented pith beams and in longitudinally oriented parenchymatic fibres and resin channels. Resin chanals are lacking in some coniferous species (i.e. they are not present in fir or yew wood).
• Wood of broadleaved species has a more complicated morphological structure compared with coniferous wood. Libriform fibres, present in a volume of 36–76%, have a strengthening function. They are relatively short, from 0.3 to 2.2 mm, with a width from 0.005 to 0.03 mm. They have a weak connection with other types of cells due to the small number of simple pit or half-pit thinned areas. Vessels, present in a volume of 20–40%, have a conductive function. Their conductive function is important for the transport of nutrients during a tree's growth, as well as for transport of preservatives and modifying substances into wood. In ring-porous species (ash, elm, hickory, oak), large vessels in early wood have a diameter from 0.2 to 0.5 mm, whilst small vessels in late wood are from 0.016 to 0.1 mm. The length of vascular systems are usually up to 0.1 m, but in some wood species this can even be several metres (e.g. as long as 7 m in oak). They are created from a long, vertical line of vessels connected via openings – simple, reticular or ranking perforations. Cell walls of vessels have circular and spiral thickenings. The conductive function of vessels decreases under the influence of tyloses (i.e. when blocked by outgrowth from the surrounding paratracheal parenchyma). Parenchymatic cells, present in a volume of 2–15%, mainly have a storage function. Longitudinal, paratracheal parenchymata (single-sided, group, vasicentric, etc.) group around the vessels and vessel tracheids and connect to them via single-sided pit pairs. Longitudinal, apotracheal parenchymata do not come into contact with the vessels. In radially oriented pith beams, several parenchymatic cells are combined with a rectangular shape, horizontal or vertical, either in morphological unity (homogeneous beam) or in morphological diversity (heterogenic beam).

Source: R., L. (2008) Ochrana Dreva (Wood Protection), Handbook, TU Zvolen, Slovakia, 453 p. Reproduced by permission of TU Zvolen.

Box 1.3 A basic preview of the anatomical structure of wood

The anatomical structure of wood

Defines

The structure of the cell walls of wood's cells:

• layering (i.e. the individual layers ML, P, S1, S2, S3 – see Figure 1.1);
• proportion and localization of the structural polymers (cellulose, hemicelluloses and lignin) and extractives in the individual layers of the cell wall.

Depends on

The wood species and the type of cell (Fengel & Wegener, 2003; Wiedenhoeft,...

Produkt-Details

• Erscheint lt. Verlag: 8.8.2016
• Sprache: englisch
• Themenwelt: Technik ► Bauwesen
• Themenwelt: Weitere Fachgebiete ► Handwerk
• Schlagworte: author • BASIC • Bauingenieur- u. Bauwesen • Civil Engineering & Construction • construction materials • Factor • Holzbau • Information • Ingenieurholzbau • Ix • Konstruktionswerkstoffe • Life • Lifetime • Materials Science • Materialwissenschaften • Methods • NATURAL • Prediction • Products • Properties • protection • Structure • Timber Construction • Wood • wood degradation • Wooden • wooden products
• ISBN-10: 1-119-10651-6 / 1119106516
• ISBN-13: 978-1-119-10651-7 / 9781119106517