Corrugations

Corrugations (wash boarding and shoving) are a type of pavement distortion. Corrugation is a plastic movement typified by ripples across the asphalt pavement surface. Shoving is a form of plastic movement resulting in localized bulging of the pavement surface. These distortions usually occur at points where traffic starts and stops, on hills where vehicles brake on the downgrade, on sharp curves, or where vehicles hit a bump and bounce up and down. They occur in asphalt layers that lack stability. Lack of stability may be caused by a mixture that is too rich in asphalt, has too high a proportion of fine aggregate, has coarse or fine aggregate that is too round or smooth, or has asphalt cement that is too soft. It may also be due to excessive moisture, contamination from oil spillage, or lack of aeration when using liquid asphalt to place mixes.