I was trained to prepare a new test today (abstract taken from another website):

The particle-size distribution, or ‘grading’, is a fundamental property for all construction aggregates and often defines the product. Grading is usually carried out by sieve analysis. The sample is passed through a sieve stack (wet or dry) and the weight proportion retained on each sieve is determined. The cumulative percentage finer than each sieve size is plotted to produce ‘grading curves’. Aggregate should be clean (free of clay, silt and dust) to ensure effective binding of cement or bitumen. Sedimentation methods may also be used to determine the grading of fines.