Transverse Cracking
A crack at approximately right angles to the center line is a transverse crack. They are often regularly spaced and caused by movement due to temperature changes and shrinkage of the asphalt with aging.
Transverse cracks will initially be widely spaced (over 50'). Additional cracking will occur with aging until they are closely spaced (within several feet). They usually begin as hairline or very narrow cracks; with aging they widen. If not properly sealed and maintained, secondary or multiple cracks develop parallel to the initial crack. The cracked edges can further deteriorate by raveling and eroding the adjacent pavement.
Prevent water intrusion and damage by sealing cracks which are more than 1/4 inch wide.
Crack Frequency - Left: cracks isolated or widely spaced. / Right: cracks (sealed), a few feet apart.
Crack Width - Left: tight cracks - hairline to 1/4". / Right: open crack - 1/2" or more.
Deterioration - Left: water entering unsealed crack softens pavement causing secondary cracks. / Right: pavement ravels and erodes along open crack.
Reflective Cracking
Concrete joints reflected through bituminous overlay.
Slippage Cracking
Crescent or rounded cracks in the direction of traffic, caused by slippage between an overlay and an under-laying pavement. Repair by removing the top surface and resurfacing using a tack coat.
Left: crescent shaped cracks characteristic of slippage / Right: loss of bond between pavement layers allows traffic to break loose pieces of surface.
Longitudinal Cracks
Cracks running in the direction of traffic are longitudinal cracks. Center line or lane line cracks are caused by inadequate bonding during construction or reflect cracks in underlaying pavement. Longitudinal cracking in the wheel paths indicates fatigue failure from heavy vehicle loading. Longitudinal cracks within one foot of the edge are caused by insufficient shoulder support, poor drainage, or frost action. Cracks usually start as hairline or very narrow (top left photo) and widen and erode with age (bottom right). Without crack filling they can ravel, develop multiple cracks and become wide enough to require patching.
Filling and sealing longitudinal cracks will reduce moisture penetration and prevent further subgrade weakening. Multiple longitudinal cracks in the wheel path or pavement edge indicate a need for strengthening with an overlay or reconstruction.
Construction Joints - Left: centerline crack (still tight). / Right: crack between lane and paved shoulder (open about 1/4").
Wheel path and Edge Cracking - Left: first stage of wheel path cracking caused by heavy traffic loads. / Right: edge cracking from weakened sub-base and traffic loads.
Advanced Cracking and Deterioration - Left: multiple open cracks at center line, wheel paths and lane center. / Right: multiple secondary cracks and erosion along center line.