What is the difference between nominal size aggregate and maximum size aggregate?

Nominal size of aggregate:

The smallest size of sieve through which the whole amount of aggregate can be passed through it.10% of the total weight of the aggregate is retained in the sieve.

Example: Take 600 gm of 20mm aggregate and allow it to pass through a 20mm sieve. In this scenario, the aggregate smaller or equal to 20mm will pass through the sieve and the rest of aggregate which are bigger than 20mm will be retained on the sieve.

If the amount of aggregate retained on sieve is less than 10% of total weight of aggregate then the nominal size of aggregate is 20mm.

Maximum size of aggregate:

The smallest size of sieve through which the whole amount of aggregate can pass through it.

Example: Take 600g sample of 25mm aggregate. This 25mm aggregate can easily pass through the sieve of 20mm, 30mm, 40mm, 50mm….. because the size of 25mm is smaller than the above sieves.

In this scenario, the smallest size of sieve through which 25mm aggregate can pass is 20mm. Therefore, the maximum size of aggregate is 20mm.