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Mid-America Transportation Center

NDOR Research on Roadway Performance and Distresses at Low Temperature

Final Report
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Researchers

  • Principal Investigator: Yong Rak Kim (ykim3@unl.edu (402)472-1727)
  • Project Status
    Complete
    Sponsors & Partners
  • Nebraska Department of Roads
  • Brief Project Description & Background
    Roadway performance and distresses at low-temperature has been overlooked in the design of pavement mixtures and structures, even though roadway distresses at low temperature conditions are major issues in northern U.S. states. Major highways and local gravel roads in Nebraska are also subjected to severe low temperature conditions followed by spring thaw every year. In mid-winter, it has been noticed that cracks are often developed transversely and longitudinally in local gravel roads. In asphaltic pavements, a number of potholes are created when moisture seeps into the pavement, freezes, expands and then thaws. As well identified, most potholes are initiated due to pavement cracks (by fatigue or thermal) and are exacerbated by low temperatures, as water expands when it freezes to form ice, which results in greater stress on an already cracked road. Therefore, processes which cannot be appropriately identified by merely accounting for the thermal cracking behavior is asphalt binder as the current specifications and the pavement design guide handle. Performance and damage characteristics at low temperature conditions need to be better understood related to structural aspects, materials, and environmental conditions altogether, since the issue is not only load-related but is durability-associated.
    Research Objective
    The primary objective of this research is to investigate performance and damage characteristics of Nebraska roadways at low temperature conditions related to properties of local paving material, structural design practices of pavement, and locally observed environmental conditions. To meet the objective, we will pursue combined efforts of laboratory tests and mechanistic modeling.
    Abstract
    Roadway distresses at low temperature conditions are the major issues in northern U.S. states. Major highways and local gravel roads in Nebraska are also subjected to severe low temperature conditions followed by spring thaw every year. In mid-winter, it has been noticed that cracks are often developed transversely and longitudinally in local gravel roads. In asphaltic pavements, a number of potholes are created when moisture seeps into the pavement, freezes, expands and then thaws. As well identified, most potholes are initiated due to pavement cracks (by fatigue or thermal) and are exacerbated by low temperatures, as water expands when it freezes to form ice, which results in greater stress on an already cracked road. Therefore, processes which cannot be appropriately identified by merely accounting for the thermal cracking behavior is asphalt binder as the current specifications and the pavement design guide handle. As an example, for the predication and characterization of low-temperature cracking behavior, the current Superpave specifications and the mechanistic-empirical pavement design guide (MEPDG) are based on the creep and strength data for both asphalt binders and asphalt mixtures. For asphalt binders, two laboratory instruments were developed during SHRP to investigate the low-temperature behavior of asphalt binders: The Bending Beam Rheometer (BBR) and the Direct Tension Tester (DTT). For asphalt mixtures, one laboratory testing device was developed: the Indirect Tension (IDT) Tester. A critical temperature is determined at the intersection between the tensile strength-temperature curve and the thermal stress-temperature curve. This approach is used in the thermal cracking (TC) model, which has been implemented in the MEPDG. The TC model has been regarded as a state-of-the art tool for performance-based thermal cracking prediction, since the TC model is based on the theory of viscoelasticity, which mechanically predicts thermal stress as a function of time and depth in the pavements based on pavement temperatures, which are computed using air temperatures. However, several limitation in the TC model have been arguably issued such as the use of the simple, phenomenological crack evolution law to estimate crack growth rate, using test results obtained from the Superpave IDT test, which does not consider crack developments related to vehicle loads and environmental conditions; thus, this model cannot fully reflect fracture processes in the mixtures and pavements that are subjected to traffic loading, moisture damage, and low-temperature conditions. Performance and damage characteristics at low temperature conditions need better understanding related to structural aspects, materials, and environmental conditions altogether, since the issue is not only load-related but is durability-associated.
    Project Amount
    $ 96,278.24
    Modal Orientation
  • Pavements
  • Structures