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Manufacture

Why fineness of cement is an important parameter?

The hydration starts at the surface of cement particles. As such, it is the total surface area of cement that represents the material available for hydration. The effect of "fineness" of cement on various parameters is discussed below:

(i) Rate of hydration increases with fineness, leads to higher rate of development of strength in initial period and heat generation.

(ii) Hydration takes place on the surface of cement particle. Finer particles will be more completely hydrated.

(iii) Increasing fineness decreases the amount of bleeding but also requires more water for workability which can result in an increase in dry shrinkage.

(iv) High fineness reduces the durability to freeze-thaw cycles.

(v) Increased fineness requires more gypsum to control setting as more C₃A is now available for early hydration.

Generally greater the fineness, greater is the rate of development of strength during the initial period and larger is the heat evolution, This is possible because greater fineness enables a larger surface of cement to come in contact with water during the initial period, although the long term effect may not be different.

In addition, the particle size also influences the hydration and strength at various ages. Particles below 5 microns hydrate within 1 to 2 days and the hydration of l0-25 micron sizes may commence only after 7 days.

FAQ

What are the “negatives” of fine cement?