text: ;Dense gradation
  :A dense gradation refers to a sample that is approximately of equal amounts of various sizes of aggregate.  By having a dense gradation, most of the air voids between the material are filled with particles.  A dense gradation will result in an even curve on the gradation graph.
  ;Narrow gradation
  :Also known as uniform gradation, a narrow gradation is a sample that has aggregate of approximately the same size.  The curve on the gradation graph is very steep, and occupies a small range of the aggregate.
  ;Gap gradation
  :A gap gradation refers to a sample with very little aggregate in the medium size range.  This results in only coarse and fine aggregate.  The curve is horizontal in the medium size range on the gradation graph.
  ;Open gradation
  :An open gradation refers an aggregate sample with very little fine aggregate particles.  This results in many air voids, because there are no fine particles to fill them.  On the gradation graph, it appears as a curve that is horizontal in the small size range.
  ;Rich gradation
  :A rich gradation refers to a sample of aggregate with a high proportion of particles of small sizes.