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Analysis of Premature Low-Temperature Cracking in Three Ontario, Canada, Pavements

An analysis of premature low-temperature cracking in three Ontario, Canada, pavements is documented and discussed. Two of the contracts consisted of a 50-mm single lift of hot-mix asphalt on recycled asphalt pavement; the third contract was a single lift overlay on a previously cracked pavement. All three pavements exhibited extensive transverse cracking during their first winter. The binders used in each of the surface courses were evaluated for possible deviations from specification requirements and for their susceptibility to cracking as a result of excessive reversible aging during cold storage. The reversible aging tendencies, as indicated by bending beam rheometer (BBR) tests after extended periods of conditioning, showed that although all three binders met the specification, they lost a considerable amount from their grade temperature as determined according to AASHTO M320 criteria. Fracture tests on the binders showed that properties in the brittle state were all considered to be poor, yet typical for unmodified materials. Fracture properties in the ductile state for the binder from the one overlay contract indicated that low resistance to ductile failure could explain the observed distress. The experience has further confirmed the need to develop an extended BBR test protocol as well as brittle and ductile fracture tests to exclude binders that will be susceptible to these types of failures for future paving contracts.