Перевести и ответить на вопросы (на языке) 1. what properties make concrete a highly used construction material? 2. what two types of aggregate are used for producing concrete? 3. is sand a coarse or fine aggregate? 4. what ingredients does the quality of concrete depend upon? 5. how long does the process of hardening the mixed components last? 6. what is the difference between the so-called in-situ and precast concrete? 7. what quality is considered to be the main disadvantage of concrete? 8. for what reason is tensile strength considered to be an important quality? 9. for what purpose are metals introduced into the structure of concrete? 10. what metals is concrete frequently combined with? 11. when did the use of ferro-concrete start? 12. would you like to live in a wooden or concrete building? why?

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