MANUFACTURING OF CEMENT, TYPES AND USE OF VARIOUS CLASSES OF THE CEMENT

The principal chemical constituent of cement are 60 to 67 percent lime, 17 to 25 percent silica and 3 to 8 percent alumina, which are intimately mixed together with water to form into a slurry, which is subsequently heated, dried calcined and ground to a very fine powder. A small proportion of gypsum is added before grinding in order to control rate of setting. Portland cement may be made quick or slow setting. If there are no special reasons which make quick setting desirable, normal setting cement should be used as quick-setting cements require exceptional care and skill in handling. There are mainly five kinds of cements. Cements are classified by their properties and chemical composition, where as ordinary Portland cement is the most commonly used cement for general engineering works. Other cements with different properties are used for particular purposes. Rapid hardening cement is, in fact, a high early strength cement. This cement has the same composition as common cement but is ground more finally and is used where high early strength is required. It sets and hardens in a much shorter time than the common cement and develops higher strength in the early stages, but the ultimate strength is about the same as of the normal setting cement. The advantages of this cement over the common cement are that formwork can be removed earlier and the structure can be loaded earlier It has in four days the same compressive strength as common cement in 28 days. Rapid hardening cement is manufactured in India in limited quantities only and its use is also very limited. It is comparatively very costlier than common cement. The setting time is about same as of the ordinary cement. This cement is useful for the repair works. This cement may also be used for the road works where it is imperative to open the road to traffic with the minimum of delay however it should not be confused with quick -setting cement:-- Er Fateh chand Guleria, Director RTI welfare Association registered number HPCD, 3552 , Bilaspur Himachal Pradesh phone number 9459334377