Block Cracking


Interconnected cracks that divide the pavement up into rectangular pieces. Blocks range in size from approximately 0.1 m2 (1 ft2) to 9 m2 (100 ft2). Larger blocks are generally classified as longitudinal and transverse cracking. Block cracking normally occurs over a large portion of pavement area but sometimes will occur only in non-traffic areas.

Figure 1: Block cracking on a low volume pavement

Figure 2: Block cracking in a residential driveway

Figure 3: Block cracking in a curbside parking area.


Allows moisture infiltration, roughness

Possible Causes

HMA shrinkage and daily temperature cycling. Typically caused by an inability of asphalt binder to expand and contract with temperature cycles because of:


Strategies depend upon the severity and extent of the block cracking:

  • Low severity cracks (< 1/2 inch wide). Crack seal to prevent (1) entry of moisture into the subgrade through the cracks and (2) further raveling of the crack edges. HMA can provide years of satisfactory service after developing small cracks if they are kept sealed (Roberts et. al., 1996[1]).
  • High severity cracks (> 1/2 inch wide and cracks with raveled edges). Remove and replace the cracked pavement layer with an overlay.

Footnotes    (↵ returns to text)
  1. Hot Mix Asphalt Materials, Mixture Design, and Construction.  National Asphalt Paving Association Education Foundation.  Lanham, MD.




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