A grinding mill generally loses its grinding efficiency remarkably at fine grinding. This is because fine particles from ground materials agglomerate and adhere to the mill liners or grinding media as coating, reducing the impulsive force of the mill. In addition, the agglomerated particles are mixed into the coarse powder in the separator and recirculated through the mill. A grinding aid prevents this agglomeration to improve the grinding efficiency. The aid is generally added to the clinker at a fixed rate from 0.01% to 0.03% before entering to a finishing mill. As a result the grinding improves by 4% to 6% per 0.01% addition of aid. The aid also improved the dispersibility and fluid ability of cement (powder) and weathering is delayed.
Grinding aids have been used successfully for decades in cement production and many other areas, such as ceramics, pigments etc. The main effect is to reduce energy consumption and increase the grinding efficiency. Additional features can be improved – e.g. powder flow ability and strength development of binders.