Rapid hardening cement is a special type of cement that achieves high strength in less time. Normally the strength achieved by conventional cements in 7 days is same as the strength achieved in 3 days. This type of cement is also called as High-Early Strength Portland Cement.
In this article we discuss about manufacture process, properties, uses and advantages of rapid hardening cement.
Manufacture of Rapid Hardening CementThe manufacture of rapid hardening cement is done dry process of cement manufacture. In this cement, lime stone and shale are used as raw material and heated at extremely high temperature to form clinkers. The lime and shale clinker is then mixed with small amount of gypsum and grinded very finely to form rapid hardening cement. All the difference of rapid hardening cement to that of ordinary portland cement is the quantity of lime stone (tri-calcium silicate )used as raw material, which gives the high early strength to the cement.
Properties of Rapid Hardening Cement
- It gains strength faster than OPC. In 3 days it develops 7 days strength of OPC with same water cement ratio.
- Its final setting times is 30 mins and final setting time is 600mins which is same as OPC.
- It emits more heat during setting, therefore this cement is unsuitable for mass concreting.
- Soundness of this cement is, Autoclave - 0.8 %, Le - Chatlier's - 10mm
- The specific surface of rapid hardening cement is greater than 3250 cm2/gm.
- This cement is lighter and costlier than OPC. Its short curing period makes it economical.
- This cement should be stored in a dry place, or else its quality deteriorates due to premature carbonation and hydration.
Uses of Rapid Hardening Cement
- It is used where formwork has to be removed as early as possible in order to reuse it.
- It is used where high early strength is required.
- It is generally used for constructing road pavements, where it is important to open the road to traffic quickly.
- It is used in industries which manufacture concrete products like slabs, posts, electric poles, block fence, etc. because moulds can be released quickly.
- It is used for cold weather concreting because rapid evolution of heat during hydration protects the concrete against freezing.
Advantages of Rapid Hardening CementThe advantages of using Rapid hardening cement are,
- It requires a short period of curing.
- It is resistant to sulphate attacks.
- Shrinkage is reduced during curing and hardening of cement.
- Rapid hardening cement is used in areas like road pavements so that the traffic can be opened early. It is also used in manufacturing precast slabs, posts, electric poles, concreting in cold countries.
- It gains high strength in the early days and the form work can be removed earlier as compared to other types of cement.
- It is a very durable cement which matches the fast pace of construction and budgets required to make projects operational.