Cooling rate as described in different cement books and guidelines for better quality of clinker production.
Fast cooling of clinker after burning at 1450oC is very important as the phases produce can be preserved and quality is maintained. The direct benefits are
- The crystal sizes are smaller, which will make easier for the clinker grinding.
- The C3S mineral is bigger when its formation reaction gets frozen more effectively.
- More MgO is present in clinker phases, It is verified that as a result of a fast cooling, the MgO solidifies in glassy state in very small sizes (<5 microns) which not generate expansion in cement. Otherwise, by slow cooling, will acquired bigger sizes that will affect expansion (Pericles formation)
- The C3A is less reactive to the setting time, decreasing the quick setting or false setting.
If the clinker is sieved in 1.0mm screen, the %age of passing will give the classification of clinker quality as tabulated.
The clinker that passes through 1 mm in the order of 15 to 20% is called Optimum clinker.
It has been seen that the clinker phases, as well as the melt formed during sintering, get effected by the rate of Cooling. It is reported that the best clinker is obtained by cooling slowly to 1250 degree centigrade followed by rapid cooling. The effects of the cooling rates on the clinker phases and their properties are summarized above and demand for rapid cooling (18 to 20oC) has been suggested.
Effect of different parameters on slow and fast cooling is given below, slow cooling 4 to 5 degree per minute and fast cooling is 18 to 20 degree per minute.
1 comment
Explanation is very clear