RAPID HARDENING CEMENT- MANUFACTURE, PROPERTIES, ADVANTAGES, DISADVANTAGES AND USES

Rapid Hardening Cement

Rapid Hardening is a special type of cement that achieves high strength in less time as compared to Ordinary Portland Cement.Normally the strength produced by rapid hardening cement in 3 days is equal to 7 days strength of Ordinary Portland Cement with same water cement ratio.

Manufacture of Rapid Hardening Cement

The manufacture of rapid hardening cement is done by dry process of cement manufacture.The raw materials such as limestone and shales are used.The limestones and shales are heated at extremely high temperature to form clinkers,then these clinkers are mixed with small amount of gypsum and grinded into very fine particles to form rapid hardening cement.

The reason behind developing early strength is the increase of Tricalcium aluminate (C3A) and Tricalcium silicate (C3S) and due to increasing the fineness (min 3250 cm2/gm) of the cement.Increase the fineness of cement and the amount of C3A and C3S will result in a higher rate of hydration and rapid gaining of strength.

Properties of Rapid Hardening Cement

1.It gains strength faster than OPC.

2.Its initial setting time is 30 mins and final setting time is 600 mins which is same as OPC.

3.The specific surface of rapid hardening cement is greater than 3250 cm2/gm.

4.This cement is lighter and costiler than OPC.

Uses of Rapid Hardening Cement

1.It is used where high early strength is required.

2.It is used where formwork has to be removed early.

3.It is used in cold weather condition because rapid evolution of heat during hydration protects the concrete against freezing. 

Advantages of Rapid Hardening Cement

1.It requires less curing time.

2.It is resistance to sulphate attacks.

3.Rapid hardening cement is used in construction of road pavements so that traffic can be opened early.

4.It is used in the manufacturing of precast slabs,posts,electric poles etc so that formwork has to be removed early as possible.

Disadvantage of Rapid Hardening Cement

1.In mass concreting rapid hardening cement is avoided because it creates a large amount of heat which may leads to stracture cracks.

2.The cost of rapid hardening cement is higher than OPC.