clinker storage

Dear Azhar,

Anything known as strength of cement is simply because hydration of clinker on the application of cement with water.

 Moreover this hydration is irreversible reaction. hydrated clinker will be devoid of any strength.

So whenever you plan to store clinker in open yard, always make preparation to safeguard it water, better you cover it with tarpauline.

Regards,

Gulam Dastgir

M.Azhar:

Is there any effect of rainy water on the clinker quality (In the storage yard) 

Hello Azhar,

As Dastgir has explained, fresh clinker will become more and more hydrated the longer it is exposed to moisture, so it is important to keep it covered.

However, if you are adding limestone as a filler in your cement, there is a solution to using partially weathered clinker without any drop in mortar strengths, as long as the L.O.I. of the weathered clinker is not greater than the contribution of the normal limestone filler content.

 For example, if your GP cement normally contains say 5% of pure limestone as mineral filler and 5% gypsum, then your GP cement L.O.I. will be around 3.3%, using fresh clinker. This LOI includes;-

1. LOI contribution of fresh clinker   = ~0.3%
2. LOI contribution of 5% gypsum   = ~0.8%
3. LOI contribution of 5% limestone = ~2.2%

Water reacts with clinker minerals to produce Ca(OH)2. For example the reaction with C3S is;-    2(3CaO.SiO2) +7H2O --> 3CaO.2SiO2.4H2O + 3Ca(OH)2

Due to the large surface area of the clinker particles (and the open pores within them)  the released Ca(OH)2 reacts fairly quickly with atmospheric CO2 to produce CaCO3 by the reaction;-   Ca(OH)2 + CO2 --> CaCO3 + H2O      Therefore what you are left with in weathered clinker is a reduced clinker mineral content and a correspondingly increased CaCO3 content. (measured by LOI)

If you are already adding CaCO3, in the form of limestone, it is a simple matter to reduce the amount of limestone mineral filler added to the cement, so as to just compensate for the extra CaCO3 in the weathered clinker. At the same time, reducing the amount of limestone filler has the effect of increasing the clinker mineral content back to its normal level.

Of course in the above example, using 5% limestone filler, it would not be possible to compensate for this extra CaCO3 if the LOI of the weathered clinker is greater than 2.2%.

Therefore, it is always best to keep your "outside" clinker covered. But if you are then forced to use it, and you already add limestone as a mineral filler, it is possible to use partially weathered clinker without any effect on mortar or concrete strengths.

You will need to continually test the LOI of the clinker being fed to the cement mill (after first drying it fully) and adjust the limestone feed according to the LOI result obtained.

Regards,

 Ted.

Dear Ted,

Your suggestion is good regarding reduced use of limestone filler with hydrated clinker.

This entails higher realization cost of product, since 5 % less limestone, directly means 5% more clinker consumption for the same product.

But ultimately we have to sacrifice something for the sake of product quality, if we having heaps of hydrated clinker.

Regards,

Gulam Dastgir