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Text 7 the problem of durability in building

Durability is a very elusive property. If the problem is regarded critically the question may be asked: What is the degree of durability required?

The durability of any material or method of construction (if we regard walls) depends upon the conditions of exposure. External weathering with rapid alteration of temperature and moisture content results in deterioration of structure and materials which would be unaffected over very long periods if used inside. It is quite unnecessary to apply the same standards to materials to be used under cover as to those for external use. The severity of the conditions of exposure depends not only on site and aspect but also on the design of a building as a whole. The shelter afforded by projecting eaves, cornices, throatings and hood moulds-very much simplifies the problem of rain exclusion and deterioration of surface finished generally. So it is necessary to take into account the increased severity of exposure to the weather.

In selection materials the practice of experience is not enough.

Experience of previous behavior is the most unreliable guide when a material is used in a novel manner. Many disastrous failures have resulted from the supposition that. An unfamiliar combination of familiar can be used with complete freedom. The technique of scientific testing of materials is more reliable. It has accumulated definite principles on which of appraisal of durability may be made.

The durability of a walling material in service depends upon its chemical composition, pore structure and to a great extent upon its mechanical strength. Materials vary in the extent to which their pores will be filled with water.

In some materials nearly the whole of the pore space may be filled, in others the water may only occupy 70 or 80 per cent of the pore space.

In certain cases the effects of frost may be rendered more severe by the presence in a material of certain salts in solution. Chemical attack and pore structure are interrelated.

Thus, it is the technique of scientific testing that should be used when the problem of reliance is concerned in the sphere of building materials.

Vocabulary notes

  1. elusive property –ухильна властивість

  2. degree of durability – ступень міцності

  3. moisture content – зміст вологи

  4. eaves – карнизи

  5. cornice – карниз

  6. to simplify – спрощувати

  7. deterioration – погіршення

  8. previous – попередній

  9. behavior – поведінка

10) to a great extent – значною мірою

11) appraisal –оцінка

12) hood mould – частина каналізаційного люка

13) throating – жолобок

Exercises

1) Find the English equivalents to the following word combinations:

потрібна міцність; залежати від умов; швидка зміна температури; для зовнішнього застосування; проект будівлі; у цілому; братии до уваги; вибір матеріалу; наукове випробування.

2) Answer the following questions:

1) What does the durability of any material depend upon?

2) What does external weathering and moisture content result in?

3) What have many failures resulted from?

4) What technique is more reliable?

5) What does the durability of a walling material depend upon?

6) How may the effects of frost be rendered?

7) What technique should be used when the problem of reliance is concerned?