Cement Process & Quality Control

1. Mineralogy of Raw Material used for manufacturing of Cement.  You need a good deal of reasonably pure limestone (or marble of chalk or othe form of CaCO3); some shale, clay, schist or other material that is mainly composed of compounds of silicon, iron and aluminium. (And if the resulting raw mis is somewhat deficient in one or more of these substances, usually expressed as oxides, for convenience, then suplementary raw materials will be needed.) The raw material mineralogy is not all that important because the manufacturing process involves finely grinding the raw materials so that they combine to form different compounds when heat treated in a semi-molten state.

2. What is Pyroprocessing in Cement Plant? This is the kiln treatment stage, when the finely ground raw meal is raised up to a temperature at which it is semi-molten. After decomposition of some clay compounds and dearbonation of the calcium carbonate, further temperature increases result in the formation of hydraulically active calcium sillcates and aluminates, and alumino-ferrite compounds.

3. Why we check residue of Raw Mix & Cement only through 90 & 212 Mic in raw mill & also for Cement Mill through 45 micron. The raw mix residue is checked to confirm that the materials are ground finely enough to combine in the kiln burning zone. The coarse particles are the most difficult to combine, and exact target residue figure will depend upon the chemical composition of that residue.

4.What are an impacts of Minor Element(MgO,Na2O & K2O,Chloride,Mn2O,P2O5,TiO2 etc ) of Raw Mix in Kiln. Mg, Mn, P and Ti are among the elements that can chemically substitute for Ca. Al, Si or Fe and so affect the mineralogy of the clinker produced from the kiln, perhaps  affecting the setting time and/or strength growth of concrete and mortar or resulting in unsound concrete, if present at too high a level. Cl, Na, K and S and/or their compounds evaporate or decompose to a greater or lesser extent during pyroprocessing and are carried back by in the gas stream to condense at lower temperatures and potentially cause more or less severe blockages. In addition, their presence in significant quantities in cement may result in quality problems that affect some or all users of the product.

5. What is meant by Closed circuit Cement Mill & Open circuit Cement Mill. Exactly what it says - coarse material goes in at one end of an O/C Mill and comes in a finer state at the other end; in a C/C system, the coarser fraction of the product is separated in a classifier and returned to the mill input for further processing.

6. What is Rosin Rammler curve & Particle Size Distribution & difference between them. PSD is a graphical curve that represents the proportions by wieght of particles in various size fractions and the RR curve is a mathematical formula that provides a useful description of that curve.

7. Difference between Particle Size Distribution & Residue. PSD is described at 6, above; a residue is the percentage of material with a particle size greater than (say) 90 microns - it is the residue that would be left upon a seive with a 90 micron mesh size.

8. Difference between Compressive Strength & Setting Time of Cement. Setting time is how long (in minutes) a fresh sample of mortar takes to become firm (as judged by dropping a standardised probe on to its surface), whereas the compressive strength of mortar or concrete (in Mega-Pascals, or kg per sq metre) is the mass that can be supported by a unit area of the set and hardened material after various periods of curing.

9. How to defective by visual or by touching the cement sample or any other method to defected cement. The presence of soft or hard lumps is undesirable.