I want to know about experiences of fineness change due to a long time of storage of bulk cement in silos. In our plant we have seen increases in Blaine from 3400 to 4000 cm2/g after about three months of storage of OPC in a silo. The cement didn't suffer any other change in its physical properties (setting, strength, flow behaviour). Since I have not found any explanation of this fact in the literature, I would like to hear some comments on this subject, in particular about the mechanism involved!
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Re: Fineness Changing
Most probable reasons for increasing the Blaine while storing the cement for three months are as given under, 1.Mixing of higher fineness material from silo vent bag filter collected material. 2.Decrease in temperature of cement while storing for long time.As Blaine determination by air permeability apparatus increase in comparision to fresh ground cement as cold cement form more dense bed than fresh ground cement.
re Fineness Changing
Did you checked the moisture of that cement. It may be the moisture content of the cement due to which you are getting more finess.
If moisture content is ok, then , agitate the sample properly and then remove any moisture/dry at 100 degree celcius, cool to room temperature in dessicator before determinination of finess.