Portland Cement. Basic Ingredients

The term ‘portland cement’ was first used in 1824 by Joseph Aspdin, a British cement maker, because of the resemblance between concrete made from his cement and Portland stone, which was much used in building in England. The first modern portland cement, made from lime and clay or shale materials heated until they formed cinders (or clinkers) and then ground, was produced in England in 1845. At that time cements were usually made in upright kilns where the raw materials were spread between layers of coke, which was then burned. The first rotary kilns were introduced about 1880.

Typical portland cements are mixtures of tricalcium silicate (3CaO · SiO2), tricalcium aluminate (3CaO · Al2O3), and dicalcium silicate (2CaO · SiO2), in varying proportions, together with small amounts of magnesium and iron compounds. Gypsum is often added to slow the hardening process.

These active components in cement are unstable, and when water is added they rearrange their structure. The initial hardening of the cement is caused by the hydration of tricalcium silicate, which forms jellylike hydrated silica and calcium hydroxide. These substances ultimately crystallize and bind together the particles of sand or stone, which are always included in a mortar or concrete mixture, into a hard mass.

The hydration of dicalcium silicate proceeds similarly but far more slowly, hardening gradually over a period of years. The process of hydration and setting of a cement mixture is known as curing; during this period heat is evolved.

Task 5

Restore the sentences. Consult the text above.

1. The first modern portland cement was made from….

2. Typical portland cements are mixtures of….

3. Some cements contain gypsum to slow…..

4. The active components in cement rearrange their structure when….

5. The initial hardening of the cement is caused ….

6. Hydrated silica and calcium hydroxide crystallize and bind….

Task 6

Answer the following questions using the information from the text.

1. Who was the first to use the term ‘portland cement’?

2. What ingredients was the first modern portland cement made from?

3. Where and when was the first modern porland cement produced?

4. What manner of cement production had been used before the first rotary kilns were introduced?

5. What is the chemical composition of typical portland cements?

6. When do the active compounds in cement rearrange their structure?

6. What substances are usually added to portland cements to slow the hardening process?

7. What causes the initial hardening of the cement?

Task 7

Fill in the gaps with prepositions. Consult the text above.

1. Typical portland cements are mixtures .… tricalcium silicate, tricalcium aluminate, and dicalcium silicate, …. varying proportions, together …. small amounts …. magnesium and iron compounds.

2. The initial hardening …. the cement is caused …. the hydration …. tricalcium silicate.

3. The term ‘portland cement’ was first used …. 1824 … Joseph Aspdin.

4. Hydrated silica and calcium hydroxide crystallize and bind together the particles .… sand or stone …. a hard mass.

5. The hydration .… dicalcium silicate proceeds more slowly, hardening gradually …. a period …. years.

Task 8

Substitute synonyms from the text above for the words in bold print. Consult Task 2.

1. The term ‘portland cement’ was first used in 1824 by Joseph Aspdin, a British cement producer.

2. The first modern portland cement was made from lime and clay or shale materials heated until they formed cinders.

3. The active components in cement are unstable, and when water is added they rearrange their structure.

4. Cement grout usually contains sand or stone.

5. When a cement mixture hardens, heat is evolved.

Task 9

Translate into English the following word-combinations.

1. Цементне тісто, бетонна суміш, тверда маса.

2. Хімічний склад, хімічний склад цементу.

3. Активний компонент, активні компоненти цементу.

4. Тужавлення, тужавлення цементу, початкове тужавлення цементу.

5. Залізо, сполука заліза.

6. Пропорція, мінливі пропорції.

7. Шлак, доменний шлак.

8. Кокс, шари коксу, розташовувати між шарами коксу.

9. Цементний розчин, тужавлення цементного розчину, процес тужавлення цементного розчину.

10. Твердіння, твердіння цементу, процес твердіння цементу, сповільнювати процес твердіння цементу.

Task 10

Translate into English using the active vocabulary and the text above.

1. Портландцемент, що вироблявся в Англії наприкінці XIX століття, складався з вапна, глинозему, або зі сланцевих матеріалів.

2. Активні компоненти цементу змінюють структуру при додаванні води.

3. Початкове тужавлення цементу здійснюється за рахунок гідратації трикальцієвого силікату.

4. Природний гіпс додають у цемент, щоб сповільнити процес твердіння.

5. Процес гідратації і тужавлення цементного розчину називається дозріванням цементу.

Task 11

Speak on the typical ingredients in the Portland cement structure.