Cement fineness has a significant bearing on the rate of hydration and hence on the rate of strength gain as well as the rate of heat evolution. Fine cement offers a greater hydration surface and thus faster strength growth. Over the years, the fineness of grinding improved. But it’s nearly settled now. Various types of cement are ground with different fineness. The fraction of particle size under 3 microns is observed to have a superior impact on the intensity at one day, while the fraction of 3-25 microns has a major influence on the strength of 28 days. Improved cement fineness is also found to increase concrete drying shrinkage.
Importance of Fineness Cement
- Cement fineness influences the level of hydration, hence the rate of increase in intensity.
- The larger the particle size, the greater the field-to-volume ratio of the substrate and therefore the greater the space usable for water-cement contact per unit volume.
- Fine cement, therefore, reacts more quickly with water and the rate of strength development and corresponding hydration heat is high.
- Fineness is an indicator of how even each granule is, contributing to a larger area of the ground and a larger area of the bottom.
- Increasing fineness can increase bleeding. Nevertheless, improved fineness can also result in more water being needed for workability, resulting in higher dry shrinkage possibilities.
- Fineness analysis is used to verify correct cement grinding and to determine the surface area of cement particles per unit mass.
Fineness Test of Cement
- AASHTO T 98 and ASTM C 115: Fineness of Portland Cement by the Turbidimeter.
- AASHTO T 128 and ASTM C 184: Fineness of Hydraulic Cement by the 150-mm (No.100) and 75-mm (No. 200) Sieves
- AASHTO T 153 and ASTM C 204: Fineness of Hydraulic Cement by Air-Permeability Apparatus o AASHTO T 192 and
- ASTM C 430: Fineness of Hydraulic Cement by the 45-mm (No. 325) Sieve.