Fineness of Cement & Importance of Cement Fineness
Fineness of Cement
The fineness of cement has a key bearing on the rate of hydration and, therefore, on the rate of gain of strength and the rate of heat evolution. The Finer cement provides a greater surface area for the hydration process and faster strength development. However, the fineness of grinding has increased over the years, and now it has got nearly stabilized.
Different types of cement are ground to different fineness. The particle size fraction below 3 microns has been found to have the predominant effect on the strength at one day, while the 3-25 micron fraction has a major influence on the 28 days strength.
An increase in the fineness of cement is also found to increase the drying shrinkage of concrete.
Testing of Fineness of Cement
Fineness test of cement can be done in two ways namely:
1)By determination of specific surface (total surface area of all the particles in one gram of cement)
by air-permeability apparatus. Expressed as cm2/gm or m2/kg. Generally, Blaine Air permeability
apparatus is used.
2)1) By sieving.
Importance of Cement Fineness
- The fineness of cement is known to affect the hydration rate and the strength of the cement. Increasing fineness causes an increased rate of hydration, high strength, and high heat generation.
- Increasing fineness will reduce bleeding. However, despite this, increased fineness can lead to more water required for workability, which results in a higher possibility of concrete shrinkage.
- The area-to-volume ratio that is increased will make more available area for water-cement reaction per unit volume.
Fineness Test of Cement