Laboratory tests - Standard test methods

AGS and AFS

Average Grain Size (AGS) and American Foundrymans
Society Average Fineness Number (AFS)

These values are calculated from the results obtained in Particle Size Analysis (Section 3.2) and give a rapid indication of the average size of the sand particles.

It is now more usual to refer to sieve size by aperture. However, the AFS number relates to and is calculated using the old BS mesh system, and effectively gives an indication of the sand type relative to the BS mesh size. See also Introduction to Section 3.2.

AFS numbers are frequently used to denote the relative grading or grade of sand supplied

The AGS gives a more accurate indication of grain size, in micrometres, and will indicate slight differences in sands having the same AFS number.

Neither value gives any indication of the spread of sizes and it is possible to have two sands which give the same AGS or AFS value but which have different grain size distributions. There is no direct correlation between the two values.

Method

From the Particle Size results, the percentage retained on each sieve is multiplied by the given factor. These are totalled and divided by 100 to give the required value.

A typical calculation is shown in Table 1 below:

(AGS/AFS values are expressed to nearest whole number.)

*Note:·

The AFS number is also referred to by some bodies and manufacturers as the GFN (Grain Fineness Number).

Previous: Particle size analysis
Next: Loss on ignition (LOI)