What is fineness of cement?

Agreed with the answers of Mr.Alex & Mr.Wolf Klaas and it can be described as follows :

Fineness of cement is property of cement that indicate particle size of cement and specific surface area. and indirectly effect heat of hydration. if fineness is more then heat of hydration should be more

specific surface expressed as total surface area in sq. cm/gm. of cement.

I agree with the previous answers

It should not exceed following percentage by weight for different types of cement.

I)Ordinary Portland cement =10%

II) Rapid hardening cement =5%

III) Low heat cement =5%

Fineness is tells about the particle distribution of cement. Fineness of is cement expressed in terms of total surface area of unit weight of of cement.

Sieve analysis ------->I.S.sieve NO.9 is used to test----->permissible limit for Ordinary Portland Cement is not more than10% retained on I.S.SIEVE NO.9

SIGNIFICANCE More the fineness ---->more water demand---->more surface area---->more rate of hydration---->more heat of hydration----->more strength developed at early stages

Agreed with the answers of  Mr.Wolf Klaas

The fineness of cement is no.of fine particles present in one surface area.

We know that cement hydrates with the presence of water. When cement is mixed with the water, a thin layer is formed around the particle. This layer grows bigger and makes cement particles to separate. Due to this, hydration process slows down. Therefore, the smaller particle will react much quicker than the larger particle. A particle with dia1µm will react entirely in one day, whereas the particle with diaµm takes about one month. So the particle size distribution is more critical in attaining the final strength of cement in allowable time. But too much of smaller particles in cement results in quick setting, leaving no time for mixing, handling and placing. So to increase the setting time of cement, cement is grinded in a different range of particle sizes. The following proportions are usually maintained in Cement: About% of the cement of fine particles is smaller than2 µm,% of wt of cement is made of particles larger than µm, and only a few wt% is particles larger than µm. Source : civilread.com