1156 posts
Re: Raw materials
TiO2 enters into solid solution in the clinker minerals until saturation is reached and then the mineral formed is 3CaO.2TiO2. Essentially the TiO2 substitutes for SiO2 in the clinker minerals therefore it should effectively reduce the lime saturation and so the free CaO content of the clinker. The opposite to the effect you are experiencing. There could be many explanations for that. Is the granulometry of the silica content in the new raw material source the same as in the old source? Are there any other minor components (alkalis, etc.) in the new source which might be affecting the mineralogy and combination?
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1156 posts
Raw materials Question 50
We are carrying out research on blended cements with a view to increase the utilisation of blast furnace slag/fly ash. In this context, we are exploring use of high energy mills (Jet Mill, Vibratory Mill etc) together with traditional milling devices. I wish to ask:
1. How important is the strength of cement? There is considerable amount of literature on high performance cement/energetically modified cement ie cement with compressive strength in the excess of 90 Mpa and concrete with greater than 145 Mpa.
2. What could be the major limitations in using mills such as Jet Mill in cement industry? We understand these mills consumes lots of energy but it is also true that the efficiency of traditional mills decreases as we approach the target size. Should not the combination work better?
3. I am looking addresses of supplier for lab size jet mill and vibratory mill (2-10 kg/h) for the grinding of cement clinker, BF slag and fly ash.
1156 posts
Re: Raw materials
The strength of the cement is important as the hydration of the cement is responsible for all the early strength development of blended cements. The hydration of the cement minerals also releases the calcium hydroxide which activates the pozzolanic reaction of the fly ash or slag. Jet mills are not used in the cement industry due to the operating costs and the throughput capabilities of the mills. Large cement plants employ mills capable of producing tens por hundreds of cement per hour. I don't think jet mills can reach that capacity? For a laboratory mill my first port of call would be ELE (Engineering Laboratory Equipment).
1156 posts
Raw materials Question 51
If air cooled slag is used as a raw material for kiln , replacing uncalcined calcium carbonate, will the calcium silicates, aluminates, etc. revert back to free state, so they can reform clinker crystals of cement design proportions? Will the existing sicates go to C2S state with the increased temperature and time. In other words could this slag combined with correction proportions of silica, iron, alumina, calcium be used as a primary raw material for a kiln feed? If there is a reversion of the state of the compound will there be a requirement for additional heat (as opposed to the exothermic heat released to compound formation) ? Would there be any big colour changes if air cooled slag was used as a primary raw material.