I believe you are refering to the 'grit' or 'grade', which is the size of the particles.
The fineness of cement has an important bearing on the rate of hydration and hence on the rate of gain of strength and also on the rate of evolution of heat. Finer cement offers a greater surface...
I'm sure there is no code for laundry tubs.
% of residue should not exceed 10% as per ASTM (American Stand Testing Machine).
aavo...enikum athariyanam