Raveling

Raveling is the dislodging of coarse aggregate in the surface of a pavement. The pavement may be showing signs of ageing and hardening and may result in the production of FOD.

Severity	Distress Example	Description
Low		Dense Mix Asphalt Pavement (shown in photo): One of the following conditions exists: (1) In a square yard (square meter) representative area, the number of coarse aggregate pieces missing is between 5 and 20; (2) missing aggregate clusters are less than 2 percent of the total examined area. In low-severity raveling, there is little or no FOD potential. Surface Treatment: One of the following conditions exists: (1) Scaled area is less than 1 percent of the examined area; (2) in case of cold tar where pattern cracking has developed, the tar surface cracks are less than 1/4 in (6 mm) wide. Porous Friction Courses: One of the following conditions exists: (1) number of missing aggregate pieces is between 5 and 20; (2) the number of missing aggregate clusters does not exceed 1.
Medium		Dense Mix Asphalt Pavement (shown in photo): One of the following conditions exists: (1) In a square yard (square meter) representative area, the number of coarse aggregate pieces missing is between 21 and 40; (2) missing aggregate clusters are between 2 and 10 percent of the total examined area. Surface Treatment: One of the following conditions exists: (1) Scaled area is between 1 and 10 percent of total area; (2) in case of cold tar where pattern cracking has developed, the tar surface cracks are 1/4 in (6 mm) wide or greater. Porous Friction Courses: One of the following conditions exists: (1) number of missing aggregate pieces is between 21 and 40; (2) the number of missing aggregate clusters is greater than 1 but less than or equal to 25 percent of the examined area.
High		Dense Mix Asphalt Pavement (shown in photo): One of the following conditions exists: (1) In a square yard (square meter) representative area, the number of coarse aggregate particles missing is over 40; (2) missing aggregate clusters make up more than 10 percent of the total examined area. Surface Treatment: One of the following conditions exists: (1) Scaled area is over 10 percent; (2) in case of cold tar, the tar surface is peeling off. Porous Friction Courses: One of the following conditions exists: (1) number of missing aggregate pieces is greater than 40; (2) the number of missing aggregate clusters is greater than 25 percent of the examined area.