Saw-Cut Joints as a Countermeasure for Low Temperature Cracks at Asphalt Pavement

Climate condition in Mongolia is severe, and air temperature in winter reaches −40 °C. Low temperature cracks (LTC) are found at asphalt pavement widely in Mongolia. Saw-cut joints with every 10, 30 and 50 m are introduced at new asphalt pavement as a countermeasure for LTC based on past research at Canada, Alaska and so on, because materials including bitumen are limited and it seems that controlling LTC in advance is cost-effective. From above test pavement results, it seems that 10 m-separation section has fewer LTC after 2021–2022 winter season. And similar cracks are found at shoulder with unbound materials. In general, frost heave occurs in severe winter and unbound materials move upward. But there is no upward movement at shoulder nor asphalt pavement. A technical paper in Japan said that the development of ice crystals due to the movement of pore water is small and shrinkage due to changes in soil structure is greater in low-saturation soil. Moisture contents of the unbound materials are low, and winter in Mongolia is dry in practice. The authors think that similar phenomena have been occurred there and they are LTC of unbound materials. Most LTC at asphalt pavement and LTC at unbound materials are connected each other. And some are at asphalt pavement only or at unbound materials only. Follow-up survey is required to know this cracking and that saw-cut joints are effective or not.