Thermal cracking of asphalts

Thermal cracking, also called low-temperature cracking, of flexible pavements is a critical issue for many highway authorities of countries with predominately low to very low ambient temperatures. 

It was as early as 1965 that Monismith et al. (1965) suggested that, in the very cold winters of Northern America, tensile stresses induced in the wearing course could exceed the breaking strength of the material and lead directly to transverse cracking of the pavement. 

Later on, Dauzats and Rampal (1987) published results that surface-initiated cracks in France were initially caused by thermal stresses and then further propagated by traffic loads. Gerritsen et al. (1987) reported that pavements in the Netherlands were experiencing premature cracking in the wearing courses and those observed outside the wheel paths were associated with asphalts having low strength characteristics at low temperatures. 

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). 

The US practice uses the creep compliance and indirect tensile strength test, according to AASHTO T 322 (2011), as a suitable performance test for low-temperature cracking in hot mix asphalt mix design. The same procedure was selected as the material characterisation test method for the prediction of low-temperature cracking of flexible pavements in the AASFITO (2008) Mechanistic-Empirical Pavement Design Guide. 

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