The breakdown of an aggregate by particle size, found by shaking a sample through a nest of sieves and recording the cumulative percent passing each one, from the largest size down to the 75-micron No. 200 sieve. Plotted on a 0.45 power chart, the curve shows whether a mix is dense-graded, gap-graded or open-graded and whether it runs coarse or fine of the maximum density line. Gradation governs VMA, workability, permeability and how prone a mix is to segregation.
Gradation's running fine on the number 8, plant must have pulled from the wet end of the screenings pile again.
Also heard as
- grading
- gradation curve
Related terms
NMAS
Nominal maximum aggregate size: the sieve size used to name a mix, such as a 9.5 mm or 19 mm mix.
Fines
The dust-sized part of the aggregate passing the No. 200 sieve, which stiffens the binder into a mastic.
JMF
Job mix formula: the approved recipe of gradation and binder content a plant must produce on a project.
Segregation
Separation of coarse and fine aggregate, or of hot and cold mix, that leaves open, low-density spots in the mat.