Sealing cracks in pavements
Introduction
Pavement cracks are fissures that develop in the surface and underlying layers of roads, highways, and other paved surfaces, primarily in asphalt concrete (AC) or portland cement concrete (PCC) pavements, due to stresses exceeding the material's tensile or shear strength. These cracks compromise the pavement's structural integrity, allow surface water infiltration that leads to further damage such as base weakening and pothole formation, and are classified by type, severity (based on width, spalling, and associated random cracking), and location (e.g., wheel path or edge).[1][2] Common in both flexible (asphalt) and rigid (concrete) pavements, they result from a combination of traffic loading, environmental factors like thermal contraction and freeze-thaw cycles, and construction deficiencies, with early detection and sealing preventing progression to severe distress.[3][1]
In asphalt pavements, key crack types include fatigue cracking, which forms interconnected patterns in wheel paths from repeated traffic loads on weak subgrades, often progressing to an "alligator" appearance; longitudinal cracking, parallel to the centerline due to poor joint construction or thermal stress; transverse cracking, perpendicular cracks from shrinkage during cold weather; block cracking, rectangular patterns from asphalt binder aging; and edge cracking, crescent-shaped fissures near unpaved shoulders caused by soil movement or overloading.[2][3] Severity is rated as low (width ≤6 mm, no spalling), moderate (>6 to ≤19 mm, minor spalling), or high (>19 mm, severe spalling or pumping), with measurements in meters or square meters for monitoring.[1] Reflection cracking occurs in overlays, propagating from underlying joints or cracks due to differential movement.[2]
For concrete pavements, cracks manifest as corner breaks at slab intersections from load stresses, durability ("D") cracking as hairline patterns near edges due to aggregate freeze-thaw expansion, longitudinal cracking from subgrade restraint, and transverse cracking perpendicular to joints from thermal contraction or curling.[1] These are assessed by width (<3 mm low, ≥13 mm high), spalling extent, and faulting (elevation differences across cracks), often exacerbated by joint deterioration.[1] In continuously reinforced concrete, transverse cracks are controlled by steel but can widen under heavy loads.[1]
Maintenance strategies focus on sealing or filling cracks wider than 6 mm to block water entry, using elastomeric hot-applied materials for working (moving) cracks or emulsions for non-working ones, applied in cool weather after cleaning and routing reservoirs.[2] Effective treatments extend service life up to 9 years but require sound underlying structure; severe cases demand overlays or reconstruction.[2] Regular distress surveys, as standardized by programs like the Long-Term Pavement Performance (LTPP), aid in prioritizing repairs to minimize safety risks and costs.[1]