L - —“D” cracking is defined by hairline cracks occurring in a limited area of the slab, such as one or two corners or along one joint.  Little or no disintegration has occurred. No FOD potential.

M - “D” cracking has developed over a considerable amount of slab area with little or no disintegration or FOD potential; or “D” cracking has occurred in a limited area of the slab, such as one or two corners or along one joint, but pieces are missing and disintegration has occurred. Some FOD potential.

H - “D” cracking has developed over a considerable amount of slab area with disintegration or FOD potential.