Cement

CEMENT

Cement is a cementing or  binding material used in engineering construction. It is manufactured from calcareous substance and is similar in many respects to the strongly hydraulic limes but possessing far greater hydraulic properties. Cement differs from lime in many respects . . cement is vary useful and superior  to lime under the following conditions and requirements.

1. For construction of structures in wet places and under water.

2. Where great strength and durability of structures are required.

2. Where mortar or plaster has to set quick and attain its strength.

4. Where hard surface is required for the protection of exposed surfaces of structures against the destructive agents of the weather  and certain organic or inorganic of chemicatls.

5.For water tightness of structure.

6. For decorative omamental and pointing works. There are two classes of cements: Natural cement and artificial cement.

Natural cement : This is manufactural by buring  and  crushing to powder natural stones containing 25 to 40 percent of clay the remainder being the carbonate of lime. Sometimes mixed with carbonate of magnesia. It is brown in colour and sets very quickly when mixed with water. It is not so strong as the artificial cement. The best variety of natural cement is know as Roman cement in England . Roman frist used powder calcined limestone as binding materials in construction works. Roman cement is not used in Bangladesh. This type of cement was fist obtained hy joseph parker in England by calcining nodules of argillaceous limestone in 1824.

Artificial cement : The best verity of artificial cement is know as ordinary to Portland due to its resemblance in colour and quarried in dorset in europ. This is also know as normal setting cement. In most of engineering works Portland cement used. In this chapter, composition, properties and the manufacturing processes of Portland cement will be dealt with. Also the  differet varieties of cement and their properties and used will be discussed briefly.