Wood and its properties = Древесина и ее свойства. Учебное пособие

UNIT 2

DURABILITY AND PROTECTION

1. Transcribe, translate and memorize the following words.

Deterioration, employment, conditions, borers, causes, corrosion, abrasion, lumber, timber, exposure, service, decay, useful, proper, financial, seawater, measures, catastrophic.

2. Check up if you remember the following verbs.

To include, to develop, to avoid, to deteriorate, to prevent, to grow, to keep, to extend, to expose, to reduce, to subject, to recover, to contain.

3. Match the following word combinations.

4. Read and translate the text into Russian.

AGENTS AND CONDITIONS

Key to the satisfactory employment of wood and wood - based products as building materials is an understanding of the agents and conditions that can lead to decay or other forms of deterioration. Wood structures, when properly designed and constructed, can serve satisfactorily for hundreds of years. As with many naturally formed organic materials, however, wood may be subject to decay, fungal stains, insect infestation,

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fire, and surface weathering, all of which can greatly reduce the useful life of buildings and products. There is no reason for wood deterioration to occur within a building where exposure to water can be controlled. Generally, wood that is used out of doors, is subjected to rain, or has contact with the ground or to seawater will eventually decay or be attacked by insects or marine borers. Service life can be greatly extended by proper treatment or species selection. To avoid deterioration in buildings or to extend the life of wood materials used under severe exposure, users of wood products must understand the conditions under which deterioration develops and the appropriate preventive measures to be taken. Biological agents are the major causes of wood deterioration. Deterioration can result from fungi that cause staining, softening, and decay; marine borers, mainly small mollusks and crustaceans; insects including termites, carpenter ants, and a variety of wood - boring beetles; and bacteria that cause deterioration in water - stored logs and foundation piles. The greatest financial losses from biodeterioration result from decay fungi. These agents of biological deterioration are most active in tropical climates, but they also develop in temperate and colder regions. Fire is the most catastrophic and economically important form of nonbiological deterioration. Less important nonbiological agents of wood deterioration include ultraviolet light and mechanical abrasion, which contribute to surface weathering; chemical agents such as strong acids or alkalies; and products of metallic corrosion that can cause wood to deteriorate around nails or other metal fasteners. Following catastrophic storms that blow down timber, salvage logging operations must mobilize quickly to recover downed trees. While much of this timber will be of high utility, value recovery is costly, blue stain may be common, and lumber may contain incipient decay and ring shake. If timber is to be recovered following a fire or windstorm, recovery efforts should generally be accomplished as soon as possible, ideally within 3 – 6 months. In dry climates, such as in arid regions of the western United States and Canada, it may be possible to successfully recover timber as long as several years following the death of trees. Hardwood trees that grow in soft soils will often uproot during severe storms. Because their root ball remains attached, the quality of wood remains higher for a longer period, often for a year or more following blow down. If the market quantity of timber is sufficiently high, then logs may be kept under sprinkler storage to prolong their life. Under such storage, logs can be kept for 6 – 9 months with little or no degrade. In some cases, water - stored logs are processed after 2 – 3 years of storage.

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[From: Shmulsky R., Jones P. D. Forest Products and wood science / R. Shmulsky, P. D. Jones. – US : Willey-Blackwell, 2011. – P. 229]

5. Define whether the following statements are true or false.

1.There are some reasons for wood deterioration to occur within a building where exposure to water can be controlled.

2.Wood which has contact with the ground or to seawater can`t decay.

3.The greatest financial losses from biodeterioration result from decay fungi.

4.Water is the most catastrophic and economically important form of nonbiological deterioration.

5.Following catastrophic storms that blow down timber, salvage logging operations must mobilize quickly to recover downed trees.

6.Hardwood trees that grow in soft soils will often uproot during severe storms.

7.In some cases, water - stored logs are processed after 5 –10 years of storage.

8.Wood structures, when properly designed and constructed, can serve satisfactorily for hundreds of years.

9.More important nonbiological agents of wood deterioration include ultraviolet light and mechanical abrasion.

10.Fungi aren`t most active in tropical climates.

6. Give the English equivalents for the words and word combinations given below and memorize them.

Гниение ли другие формы разрушения, продлить жизнь дерева, качество древесины, гниение грибов, небиологический тип разрушения, морская вода, заготовленные бревна.

7. Give the Russian equivalents for the words and word combinations given below.

Decay fungi, ultraviolet light, soft soil, death of trees, quantity of timber, incipient decay, small mollusks and crustaceans, appropriate preventive measures, nonbiological agents, market quantity of timber, wood deterioration.

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8. Fill in the gaps.

1.Wood structures, when properly designed and constructed, can

…………….for hundreds of years.

2.Value recovery is costly, blue stain may be common, and ……..may contain incipient decay and ring shake.

3.Biological agents are the major causes of wood………….

4.Fire is the most catastrophic and economically important form of

……………..deterioration.

5.Following catastrophic storms that blow down timber, salvage

……………..must mobilize quickly to recover downed trees.

6.Hardwood trees that grow in soft soils will often ………during severe storms.

7.If the market quantity of timber is sufficiently high, then logs may be kept under ………….to prolong their life.

8.If timber is to be recovered following a…………, recovery efforts should generally be accomplished as soon as possible, ideally within 3 – 6 months.

9.In dry climates it may be possible to successfully recover …….as long as several years following the death of trees.

10.Logs may be kept under sprinkler storage to…………..

9. Translate the following sentences from Russian into English.

1.Нет причин разрушения древесины внутри здания, где воздействие воды можно регулировать.

2.Как правило, древесина, используемая вне здания, подвергается воздействию дождя, или имеет контакт с землей или с морской водой, в конечном счете, может подвергнуться гниению или нападению насекомых.

3.Для того, чтобы избежать разрушения древесины в зданиях или продлить срок службы древесных материалов, используемых при интенсивном воздействии, пользователи древесной продукции должны учитывать условия, при которых развивается разрушение.

4.Ухудшение может быть результатом грибов, вызывающих окрашивание, смягчение, и распад древесины.

5.Наибольшие финансовые потери от результата биоповреждений происходят от грибков.

6.Менее важные биологические агенты, не приводящие к износу древесины, включают ультрафиолетовый свет и механическое трение.

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7.Виды деревьев, растущие в мягких почвах, часто ломаются во время сильных штормов.

8.Бревна могут храниться в течение 6 - 9 месяцев.

10. Translate the following phrases.

Воздействие дождя, wood materials, моллюски и ракообразные, sprinkler storage, высокий уровень практичности, recovery efforts,

гниение древесины, fungal stains.

11. Check yourself with the following questions.

1.What is the key to the satisfactory employment of wood and wood - based products as building materials?

2.How long could wood structures serve if they were properly designed and constructed?

3.What are the reasons for wood deterioration?

4.How can we avoid deterioration in buildings or extend life of wood materials?

5.Which agents of biological deterioration are the most active in tropical climates, but also able to develop in colder regions?

6.What kinds of trees are more likely to uproot during severe storms?

7.When may logs be kept under sprinkler storage to prolong their life?

8.Which regions is it possible to recover timber successfully in?

12. Make a summary of the text.

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UNIT 3

WOOD DECAY

1. Read the following words and state what Russian words help to guess their meaning.

Approach, appropriate, product, building, region, percent, equilibrium, humidity, species, appearance.

2. Check up if you remember the following verbs.

To avoid, to design, to prevent, to dry, to remain, to keep, to pressure, to associate, to resist, to moderate.

3. Match the following word combinations.

4. Read and translate the text into Russian.

PREVENTING WOOD DECAY

There are three general approaches to preventing wood decay. Each is appropriate under certain situations. First, there are three rules: keep the

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wood product dry. This is usually the most effective and least expensive approach. If wood buildings in temperate regions of the world are properly designed to avoid condensation and leakage problems, the wood can last indefinitely. Building design and maintenance are key components of increasing longevity of wood components. The use of prudent roof designs that minimizes valleys and other potential water traps, incorporates liberal overhangs, utilizes gutters, and keeps wood siding and trim 45 – 75 cm (18

– 30 in.) off of the ground can dramatically reduce maintenance costs and add years to building life. Inside buildings in temperate climates, wood equilibrium moisture content (EMC) is never high enough to maintain wood at 20 percent MC unless condensation, water leaks, crawl - space moisture or some other unusual factor(s) is present. In tropical countries, where rainfall and humidity are high, it may not be possible to maintain wood buildings in an adequately dry condition to prevent decay. The avoidance of deterioration by maintaining a low moisture content is not possible for wood in contact with rain, the ground, or other materials that may remain damp, such as concrete or stone. Second, where it is not possible to keep wood dry, wood should be treated with chemicals that inhibit fungi. If the moisture content cannot be maintained below 20 percent, the use of preservative - treated material is the most practical way to avoid decay. Various chemical treatments are available. The level of treatment can be varied to suit the application and expected severity of the decay hazard. The American Wood Protection Association (AWPA) has developed standards for pressure - treated wood to be used in a variety of situations. Third, in some cases, it is possible to use naturally decay - resistant species rather than using preservative - treated wood. It is important to note that only the heartwood of naturally decay - resistant species is resistant to decay and that the current durability performance associated with these is not as good as it has been historically, mainly due to the increasingly young age at which the trees are harvested. Because of the limited availability and high cost of naturally decay - resistant species as lumber, this approach is most suitable for applications where both durability and appearance are important. Historically, woods such as cypress, greenheart, cedar, redwood, and teak were often used where a combination of decay resistance and natural appearance was desired. Examples of such applications are the use of western red cedar, redwood, or resistant tropical species for the construction of patio decks and privacy fences. The commonly used construction woods - Douglas fir, southern pine, fir, larch, hemlock, and spruce - have moderate to low resistance to decay. Thus, these species must be treated to obtain a

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suitable degree of decay resistance. The degree of natural resistance to decay exhibited by heartwood depends largely on the nature and amount of fungitoxic extractives in the species. The amount varies considerably within a species, location in the tree, age, and rate of growth. Hydrophobic extractives and other cell - occluding materials (tyloses) can improve decay resistance by decreasing permeability, thereby keeping wood moisture content low. Rapidly grown second - growth timber, which is most commonly available often, has a lower extractive content, and thus lower natural decay resistance, than older slow - growth material. Also, there are kiln drying and steaming techniques available that can darken many species, thereby making the sapwood appear like heartwood. Thus, extreme caution and care should be exercised when specifying “naturally durable” species.

[From: Shmulsky R., Jones P. D. Forest Products and wood science / R. Shmulsky, P. D. Jones. – US : Willey-Blackwell, 2011. – P. 237]

5. Read the following statements and define whether they are true or false according to the text.

1.Keeping the moisture content at a low rate is always a good solution.

2.There are three general approaches to prevent wood decay.

3.Keeping the wood product dry is the least expensive solution.

4.Where it is not possible to keep wood dry, wood should be treated with

5.Chemicals that inhibit fungi.

6.Building design and maintenance are not important for maintaining the longevity of wood.

7.The heartwood of naturally decay - resistant species isn`t resistant to decay.

8.Hydrophobic extractives and other cell - occluding materials (tyloses) can`t improve decay resistance.

9.The degree of natural resistance to decay depends largely on the nature and amount of fungitoxic extractives in the species.

10.There are kiln drying and steaming techniques available that can darken many species.

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6. Give the English equivalents for the words and word combinations given below and memorize them.

Длительность, период службы древесных материалов, основные компоненты, гниение, конкретные ситуации, разрушение, дорогостоящий способ, расходы на обслуживание, протечки.

7. Give the Russian equivalents for the words and word combinations given below.

Decay, approach, deterioration, longevity, maintenance costs, appropriate, to prevent, moderate, equilibrium, leakage problems.

8. Fill in the gaps.

1.If wood buildings in temperate regions of the world are properly designed

……………and……………, the wood can last indefinitely

2.The use of prudent roof designs that minimizes valleys and other………………, incorporates liberal overhangs, utilizes gutters.

3.It is important to maintain wood at 20 percent MC unless condensation, water leaks, crawl - …………or some other unusual factor(s) is present.

4.In tropical countries, where rainfall and humidity are high, it may not be possible ………………in an adequately dry condition to prevent decay.

5.Wood can be in contact with rain, the ground, or other materials that may remain……., such as concrete or stone.

6.If the moisture content cannot be maintained below 20 percent, the use

…………..- treated material is the most practical way to avoid decay.

7.The American Wood Protection Association (AWPA) has developed

………………- treated wood to be used in a variety of situations.

8.In some cases, it is possible to use naturally decay - ………….rather than using preservative - treated wood.

9.The commonly used construction woods — Douglas fir, southern pine, ….., larch, ……., and spruce — have moderate to low resistance to decay.

10.Thus, these species must be treated to obtain a suitable degree of

………resistance.

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9. Translate the following sentences from Russian into English.

1.Существуют три основных подхода к предотвращению гниения древесины.

2.Каждый из подходов является подходящим в конкретной ситуации.

3.Существуют три основных правила, которые нужно соблюдать.

4.Необходимо хранить древесину в сухом месте.

5.Это один из самых недорогостоящих способов продлить срок хранения, а также, наиболее эффективный.

6.Не все регионы спроектированы таким образом, чтобы удавалось избежать конденсации и проблем с протеканием.

7.Проектирование строения – это ключевой фактор, который способен продлить жизнь древесины.

8.Процент содержания влаги в древесине внутри помещения никогда не является достаточным.

9.Не всегда возможно избежать разрушения древесины, поддерживая низкий процент содержания влаги.

10.В случаях, когда не представляется возможным поддерживать дерево сухим, его необходимо обработать химическими веществами.

10. Translate the following phrases.

Конкретные ситуации, longevity of wood, проблемы протечки , expensive approach, основные компоненты, wood decay, region, избегать конденсации, to pressure, дорогостоящий способ.

11. Check yourself with the following questions.

1. How many general approaches are there to prevent wood decay? 2. What rules are there to keep wood dry?

3. What affects the longevity of wood?

4. Is it always possible to keep the wood dry?

5. Can you name three key points the author draws our attention to.

12. Make a short summary of the text.

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