12 TRANSVERSE CRACKING Transverse cracking is a type of asphalt pavement damage that occurs when cracks run perpendicular to the pavement’s center line. Transverse cracking is primarily caused by shrinkage of the asphalt and its inability to resist thermal expansion and contraction without cracking. It may be related to: • Loss of volatile compounds in the binder over time. • A high content of lime and fly ash, which increases drying and temperature shrinkage deformation. • Freshly laid hot asphalt meeting cold air. • Reflection from underlying layers. To prevent transverse cracking, you can: • Follow design and construction best practices. • Avoid laying asphalt in cold weather. • Maintain a surface treatment on the asphalt to preserve its flexibility. Tips on responding to block cracking: • If the cracks are working cracks (defined by thermal expansion/contraction of more than 0.1”), consider routing the cracks before sealing them to allow for better adhesion of the sealer material. • Fill cracks soon after they appear to prevent the intrusion of water under the asphalt. • Milling the upper portion of the asphalt to the depth of the crack (which will have lost much of its volatile binder compounds) prior to placement of a new HMA layer can improve performance, especially in cases of severe transverse cracking.
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