Cracking in flexible pavements

The forms of surface cracking vary and are attributed to various reasons. They can be hairline cracks, line cracks, line cracks with branches and block cracks. 

The extent and severity of cracking as well as their detrimental effect on the pavement structure determine the appropriate maintenance treatment. 

The above treatments are indicative. The best approach relies on determination of the cause(s), extent of cracking and average crack width. 

Crack sealing/filling is only applied to crack widths greater than 3 mm. Cracks with width less than 3 mm (hairline cracks) are treated more effectively by micro-surfacing, surface dressing (chip seal), sand seal or fog seal. 

The crack sealing procedure consists of either just cleaning and sealing the crack or sawing or routing, cleaning and sealing the crack with an appropriate sealant. 

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In a recent study (Romero et al. 2011) on the premature surface cracking in flexible pavements in Utah, it was reported that the cracks were not attributed to pavement structural deficiency but to the low-temperature performance of the bituminous mixtures. Numerous other studies have found that the main form of deterioration in asphalt pavements within the freezing areas of the United States and Canada is thermal cracking (Marasteanu et al. 2007). 

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