4.5 : セメントの細かさ

The size distribution curve of cement indicates its fineness by showing the proportion of particles of varying sizes. The curve rises steeply, indicating a significant portion of fine particles. Around 90 percent of the cement particles are smaller than 2.36 mils.

Hydration of cement initiates at the surface of the cement particles. The finer the cement, the greater the surface area, leading to faster hydration and strength development.

The fineness of cement is the total surface area of cement particles per unit weight of the cement.

The Blaine air permeability test is commonly used to determine the specific surface area of cement.

For this, cement is packed in a cell at a specific density, and a partial vacuum is created, causing a definite volume of air to be drawn through the cement bed. The time taken for this is measured, and the specific surface area of cement is calculated.

Also, dry sieving a definite mass of cement through a 45-micron sieve and measuring the weight of residue retained on the sieve gives the fineness of the cement.