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Lime and sand

Lime and sand are natural materials. Both of them are used for producing artificial building materials such as cement, mortar and concrete blocks.

Of the several varieties of lime, that used chiefly for brickwork and masonry is known as hydraulic lime. It is produced of limestone or chalk which is burnt in the kiln for three or four days; then it is ready to be made into mortar.

Hydraulic lime contains a large percentage of lime silicate, aluminate that gives the material the property of hardening under water and at the same time it contains so much free lime that the burned mass will slake upon the addition of water.

Sand obtained from pits or quarries is the best for mortar because of its angularity (called “sharp”); failing this sand from river banks or beds is used. Sea sand is unsuitable for mortar as it contains salts which attract and retain moisture, in addition to producing a whitish powder or efflorescence which discolours the brickwork or masonry. Sand should be well graded, clean, sharp and free from loam, clay or other impurity. Dirty sand never be used as it may reduce the adhesive value of the mortar considerably, and in order to ensure a clean sand it is frequently specified that it should be washed.

2. Answer the following questions:

1. What are lime and sand used for? 2. What lime is chiefly used for brickwork and masonry? 3. How is hydraulic lime produced? 4. What does hydraulic lime contain? 5. What gives the material the property of hardening under water? 6. What sand is the best for mortar? Why? 7. Is river sand as good as quarry sand? 8. Why sea sand is unsuitable for mortar? 9. Why sand should well graded, clean, sharp and free from loam, clay or other impurity?

III. Comprehension and Word Study.

1. Look through the text again, find all sentences with Passive Voice and translate them. Change them into Active Voice.

2. Translate into Russian.

Of several varieties of lime; is known as hydraulic lime; contain a large percentage; burned mass; addition of water; unsuitable for mortar; attract and retain moisture; whitish powder; to reduce the adhesive value; it should be washed.

3. Say it in other words:

Model: Cleanliness of sand is most essential.

Cleanliness of sand is very important.

1. The presence of dirt reduces the strength of mortar. 2. Tests have shown that the shape of the particles is important. 3. Some river sands may be deficient in fines. 4. Sea sand is unsuitable for mortar as it contains salts. 5. Sand should be clean from impurity.

4. Say whether it is true or false:

1) Loam is chiefly used for brickwork and masonry. 2) Quarry sand is obtained from river beds. 3) Sea sand is suitable for mortar. 4) Salts attract and retain moisture. 5) Dirty sand reduces the adhesiveness of the mortar.

5. Put general and special questions to each sentence:

1. Sandstone is not so durable as limestone.

2. It is strong enough to be used as a building stone.

3. Hydraulic lime contains a large percentage of aluminate.

4. This burned mass will slake upon the addition of water.

5. The sand for mortar was quarried in a pit not far from here.

6. The worker decided to add some more water into the mortar.

6. Translate into Russian, paying attention to the words that and one.

1. One should know that the weight of an oxygen atom is 16 times that of a hydrogen atom. 2. The best kind of sand for producing is that quarried in the river beds. 3. The mixture is identical with that mentioned above. 4. This lime doesn’t slake so quickly as the burnt one. 5. The voids are larger in sand in which the particles are of uniform size than in the one which contains a variety of particles size.

7. Translate into English:

1. Имеется несколько разновидностей извести. 2. Гидравлическая известь используется в основном для кирпичной кладки. 3. Ее производят из известняка или мела. 4. Мел обжигают в печах в течение трех или четырех дней. 5. Обожженную массу измельчают (is reduced to) в порошок, который гасится добавлением воды. 6. Песок, используемый для раствора, должен быть чистым.

IV. Post-reading Activities.

1. Discuss with your partner the text “Lime and Sand”.

2. Be ready to speak about “Lime and Sand”.

V. Supplementary Reading.

1. Read and translate into Russian without using a dictionary:

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