What is the effect to cement fineness when using shale instead of limestone?..
norew
Shale vs Limestone
Ted Krapkat
Hello Norew,
Both limestone and shales generally have a similar hardness (3 to 4 on Mho's scale), but it would depend on the grindability (comparative brittleness) of the shale compared to that of the limestone it was replacing.
The only way to know for sure, in a given situation, would be to do some lab mill grinding tests, or better still some cement mill plant trials.
Regards,
Ted.
haliff
Hi Ted,
Please with limestone you have to deal with LOI, with shale is the concern just INSOLUBLE RESIDUE(IR)?
What is the maximum allowable limit for cement IR, and what is the effect if too high.
Ted Krapkat
Hello Haliff,
Yes, Insoluble Residue would be quite high if using shale as a mineral additive in OPC cement, but IR is also high in pozzolanic cements, which logically have no limit at all on the IR.
Some shales are naturally pozzolanic, and if not they can be converted to a pozzolanic material by calcining.
So you are right, it would be difficult to sell cement with shale as a mineral additive as OPC cement because the IR limit for OPC is 0.75% in the ASTM standard and 1.5% in the British standard. However, if the shale is pozzolanic, you can add as much as you would with flyash blended cements for example.
Regards,
Ted.