Clinker Stored in an Open Yard

Sir Reactionn in free lime test is as below:- Free CaO+CH2OH-CH2OH.........> (CH2O)2Ca + H2O (CH2O)2Ca+2HCl......>CaCl2+CH2OH-CH2OH Thus if clinker is wet than Ca(OH)2 will release and that will require addtional HCl to form CaCl2 thus free lime will be higher in wet clinker This is the reason that even glass ware must be dry used for free lime test so that proper value of free lime can be obtain am i right or wrong???? Any body can coorect my reply Regards Dilip Yadav

Hello Norew,

Dilip is quite correct in that water will affect the Free Lime result of the glycol/ethanol method due to the reaction of Ca(OH)2 with the acidic titrant used.

However, drying the clinker will only prevent reaction of moisture with the clinker minerals to produce further Ca(OH)2.  There would most certainly have been significant release of Ca(OH)2 already, if the clinker was exposed to moisture.

In fact, depending on the duration of outside storage and degree of wetting, there would no doubt be significant quantities of CaCO3 present, due to the reaction;-

Ca(OH)2 + CO2  --> CaCO3 + H2O

This reaction frees water which may react with more clinker minerals to produce further Ca(OH)2 and so on. Ultimately all of the Ca(OH)2 exposed to the atmosphere will be converted to CaCO3, however this may take several months.

So, it depends on how long the clinker has been exposed as to which form the "Free Lime" takes. This form is important because free Ca(OH)2 has no effect on expansion of cement, whereas free CaO does.

The best way to distinguish between CaO and Ca(OH)2 is by XRD. Most modern XRF analysers for cement plant use also have an XRD optional extra, which will easily and quickly differentiate between the amount of CaO and Ca(OH)2 (or even CaCO3) present in clinker or cement.

Hope this helps...

Regards,

Ted.

 

Prior to storage fCao is only 1.98 several days after it was placed in our open yard fCaO rose to 3.57 that was after drying.