4.5 Blaine – A Traditional Way to Determine the Cement Strength:
The early strength is dependent on both chemistry and fineness of cement. Many
plants still characterize the cement fineness using an air permeability method (an
analysis of Specific Surface Area) introduced in 1940’s to measure the Blaine
number, a parameter related to the particle size and therefore, final cement
strength. Although this method is sensitive to the generation of fines, it does not
provide the entire picture of quality and grade of cement.
One of the limitations of Blaine is that it provides a single number representation
of a sample rather than the particle size distribution. Two cement samples, each
with a different particle size distribution, can give the same Blaine yet perform
differently in the field, because of the relative proportions of fines or oversized
material. To overcome this problem, the link between early strength and key
particle size parameters must be established for better process control.
4.6 Measurement of Particle Size Distribution – An Accurate Method of Quality Control:
The correlations between particle size and cement performance gives additional
insight for improving product quality. Particle size directly impacts strength by
controlling the rate of cement hydration because it affects specific surface area.
Reduction in the particle size increases rate of hydration and strength. On the
other hand, grinding cement to smaller sizes requires additional energy costs,
creating a critical need for measurement and control of final product size. The On
line particle size analyzer gives real time results of particle size distribution and
provides real picture of quality of finished cement. The major advantages are
indicated in below paragraph.
4.7 Advantages of On Line Particle Size Analyzer (PSD):
- PSD tenders on line measurement of cement quality by keeping a constant
‘eye in the process for real time events detection. Generally, cement quality
measurement is done manually on hourly based sampling. The variation
observed in the cement quality has been dispatched to the finished product
silo till the corrective action is initiated. Hence, consistent quality assurance
through manual system is not possible. - On line PSD gives measurement of cement particle size distribution as per
particle chemistry of material. A good particle size distribution leads to the
bonding strength of cementing material. In conventional method, cement
quality is assured through Blaine apparatus which works only on air permeability
principle. This method of measurement is only a thumb rule & does not reflect
an accurate quality parameter. - On Line PSD with Expert process control system minimizes the Relative Standard
Deviation (RSD) to 1-2%, as against the conventional Blaine method where it is
between 6-7%. - As online PSD provides the results online, the corrective action can be done
immediately and the clinker grinding can be optimized which in turn saves the