The Effect of Grinding Aids

It is commonly accepted that these admixtures are adsorbed on the surface of clinker grains reducing the hardness and prevent the agglomeration. A small addition of grinding agents, usually 0.01-0.1 % rises the output of mills of 15 %, in some cases even of 25 % the energy consumption lowering is the same. 

The addition of grinding aids leads to the increased mobility of cement, even of high fineness. The material becomes very transportable, easily flows out from silos and is without difriculties packaged into the bags. On the other side, the fine fraction content in cement increases the dustiness of the air venting the mill and worsening the electrostatic precipitators efficiency by the higher resistivity of cement, which rise from 10 to 10 cm is observed [151]. 

51 the effect of different grinding aids on the specific surface of cement is presented. As it is shown the poly-glycol-phenol ether and the heptane-phos-phonate acid have the strongest impact. The effectiveness of saturated fatty acids and alcohols action grows with the rednction of chains length, the undersaturated acids are more active than the saturated ones [152,153]. This can be explained by 

2 hepanophosphonic acid, 3 triethanoloamine, 4 sodium stearate, S sodium salt of hydroxamoic acid, 6 decanol, 7 potassium butylxanthoge-nate, 8 sulphite lye, 9 sodium cetylsulphite, 10 K HPO,  

The second reducer tin(II), also often added in the form of sulphate, is stronger reducer and less susceptible to oxidatioa Therefore the addition of tin can be lower in the case of Fe(II) sulphate from 0.2 to 0.3 %, while in the case of Sn(II) sulphate about 0.02 % or sometimes even less. The tin(ll) sulphate can be also oxidized during the storage in cement silos, however, this process occurs very slowly. That is why the producers can guarantee the Cr(VI) content below the 2 mg/kg of cement for one year, while in the case of sulphate Fe(ll) this period is shortened to two months. Mn(ll) sulphate is a good reducing agent which also is difficult for oxidation. However, it did not found industrial application till now. 

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Table IX Examples of the Effect of Grinding Aids in Dry and Wet Grinding Systems (21).

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