4. Look for the Complex Subject. Translate the sentences.

Models:

1. She seems to work hard. – Кажется, она много работает.

2. He is known to be a good engineer. – Известно, что он хороший инженер.

3. The seminar is sure to have been held. – Разумеемся, семинар состоится.

1. Granite and marble are considered to the most suitable materials for the monuments. 2. Limestone is known to be of grayish colours, in the main. 3. Stone is considered to be a hard and durable building material. 4. Limestone is known to be used for making quicklime and cement. 5. Marble and chalk are determined to have uniform structures. 6. Limestones are found to be good for constructing foundations and load-bearing walls.

5. Translate the sentences with Infinitive:

1. The term “cement” is usually taken to mean various forms of Portland cement. 2. To deliver cement for small jobs stout paper bags are used. 3. Small addition of gypsum are used to control the setting properties. 4. It is necessary to distinguish between “setting” and “hardening”. 5. Cement products are difficult to decorate with oil paints, particularly when they are new. 6. The work must be arranged to allow quick placing after mixing.7. To determine the time of setting is important for further work. 8. A special instrument is used to determine the time of initial and final set of cement.

III. Reading Comprehension.

1. Read and translate the text: types of portland cement

Rapid-hardening Portland cement is true Portland cement. Its chief characteristics are the comparative rapidity with which it gains in strength in the early stages of hydration. The ultimate tensile stress shall be not less than 300 lb. per sq. in. after one day, and 450 lb. per sq. in. after three days. The compressive strength shall be not less than 1,600 lb. per sq. in. after one day and 3,500 lb. per sq. in. after three days.

The initial setting time is less than five minutes and the final setting time is not more than thirty minutes. Rapid-hardening cement can be employed in cold weather, as it is less liable than ordinary cement to damage from frost.

White Portland cement. The chemical composition and characteristics of white Portland cement are similar to those of ordinary Portland cement except that the latter is of a grey colour. The colour of white cement is due to the raw materials used and special precautions taken in its production. The materials are pure limestones and china (white) clay, the iron oxide content is less than 1 per cent. White cement is more expensive than ordinary cement. It is used in places where for ornamental purposes the white colour is desirable.

Portland blast-furnace cement. This is a mixture of ordinary Portland cement and blast-furnace slag. The slag is mixed with ordinary cement clinker and passed to a ball mill for thorough incorporation and fine grinding. The proportion of a slag must not exceed 65 per cent, and that of Portland cement clinker not less than 35 per cent.

High alumina cement. It is dark brown in colour. It contains about 40 per cent each of lime and alumina with about 15 per cent of iron oxides. This cement sets at about the same rate as Portland cement but gains strength very rapidly. Owing to the chemical activity after hardening, for the first 24 hours it requires very wet curing conditions. This cement is several times more costly than ordinary Portland cement.