Building Materials

Cement

Introduction:

Cement is a binding material used in manufacturing concrete, it reacts with water and binds the aggregates (coarse and fine aggregates) present in the concrete mix.

Manufacture:

The process of manufacture of cement consists of grinding the raw materials finely, mixing them throughly in certain proportions and then heating them to about 1480 C in huge cylindrical steel rotary kilns 3.7 to 10 m in diameter and 50 to 150 m long and lined with special fire bricks.

The heated materials sinter and partially fuse to form nodular shaped materials called clinker. The clinker is cooled and ground into fine powder after mixing with 3 to 5 % gypsum added to regulate the setting time to form Portland Cement.  It is then loaded into bulk carriers or packages into bags typically weighing 50kg.

Two different process knows as Dry and Wet are used to manufacture Portland cement. In addition a semi-dry process is also used. Most modern cement factories use either the Dry or a Semi-dry process.

Cement Making Process: Please Check out the link below for an Animated Cement Plan Tour

http://www2.cement.org/basics/images/flashtour.html

This link will give you a good idea about the below stages of manufacture of cement:

  1. Quarry.
  2. Proportioning, Blending and Grinding.
  3. Pre-heater tower.
  4. Kiln.
  5. Clinker Cooler and Finish grinding.
  6. Bagging and shipping.

Types of cement:

  1. Portland Cement.
  2. Portland Pozzolona Cement.
  3. Portland Slag Cement.

Storage of Cement:

Cement is very finely ground and readily absorbs moisture, hence care should be taken to ensure that the cement bags are not in contact with moisture. They should be stored in air tight and water tight sheds. Cement stored for a long time tends to lost its strength (loss of strength ranges from 5 to 10% in three months to 30 to 40% in a year). It is better to use the cement within 90 days of its production.

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