1156 posts
Quality control Question 3
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.
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1156 posts
Re: Quality control
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
1156 posts
Re: Quality control
C3S is the mineral providing the early strength of the cement. If it rises the one-, two-, three- and seven-day strength will rise and vice versa. C2S is the mineral providing the later strength. If it rises then this should rise, however if it rises at the expense of C3S then you will lose early strength.
C3A causes the initial setting of cement. However hydrated C3A is susceptible to attack by sulphates in the ground water. Sulphate resisting cement therefore limits the C3A content to a maximum of around four per cent.
C4AF is important for manufacturing cement clinker as this is the first mineral to form a liquid in the kiln and therefore flux the clinker formation.
The Bogue method of calculating the content of these minerals is only another way of mathematically representing the oxide content of the clinker or cement. LSF, SM and AM are also just further methods of representing the oxide composition of the clinker or cement. High LSF means high C3S. High SM means high total C3S and C2S. Low AM means low C3A.