Rapid hardening cement:

Rapid-hardening cement is finer than ordinary Portland cement. It can be obtained by

increasing the track calcium silicate and reducing the dicalcium silicate. As per IS-8041 specific surface area of rapid-hardening cement, should be less than 3250cm²/gm.

The 1-day strength of RHC  is equal to the 3-day strength of ordinary Portland cement and the three-day strength of RHC cement is similar to 7 days strength of ordinary Portland cement. 

Manufacturing of rapid hardening cement:

Generally, cement manufacturing is done in three steps mixing of raw material burning, and fine grinding of cement clinker. 

After mixing the raw materials like lime shale iron oxide etc in appropriate proportion, it burned at high temperatures in kilns. At high-temperature chemical reaction is done and forms cement clinkers. 

Grinding of clinker: 

Once burning is done no cement clinker is fine grinding in a ball mill or tube meal. During grinding the cement clinker a small amount of gypsum by the weight of cement is added to prevent flash setting property of cement. 

As per IS-8041, no material shall be added after burning other than gypsum.

Now rapid hardening cement is ready to use.

Property of Rapid Hardening Cement: 

The following properties of rapid hardening cement as per IS-8041 are given below:

• The initial setting time is not less than 30 minutes or half hours and the final setting time is not more than 600 minutes or 10 hours.
• The soundness test results of Le-Chatelier and the autoclave are not more than 10 mm and 0.8 % respectively. i.e.  Le-Chatelier result less than 10 mm  and Autoclave result  less than 0.8% 
• The specific surface area of rapid hardening cement cell is not village than 3250 cm²/gm
• The 1-day strength of rapid hardening cement is equal to the 3-day strength of ordinary Portland cement and the three-day strength of rapid hardening cement is similar to 7 days strength of ordinary Portland cement. 

Plain Cement Concrete

Use of Rapid hardening cement:

Rapid hardening cement is used where it requires early high strength, constructing the road payment, cold weather conditions, and Frost conditions. It is also used where thornwork has to be removed as early.

Advantage of rapid hardinge cement 

• It gains strength rapidly.
• It requires less time to curing.
• It gives resistance to the sulphur attack on the structure.
• It is useful for cold weather conditions and Frost conditions. 
• It speeds up the construction work.
• It is more durable. 
• It is used at high-traffic road repair work.

Disadvantage Of Rapid hardening cement:

The cost of RHC  is 10 to 15% higher than ordinary Portland cement.
So RHC is expensive as compared to ordinary Portland cement.