Thermal fatigue cracking occurs when the daily temperature cycles cause reoccurring tensile
stress at the bottom of the Hot Mixed Asphalt (HMA) layer. Hence, daily temperature variations
are considered to be a direct impact of environmental factors on flexible pavements. These
stresses may not exceed the tensile strength of the asphalt but, when repeated over time, cyclic
loading will cause occurrence of thermal cracks. Therefore, it is necessary to experimentally
quantify the range of variation for thermal-induced strains in order to evaluate the impact of
daily and seasonal temperature fluctuations on the thermal fatigue cracking.
This paper attempts to investigate the thermal-induced strains in longitudinal, transverse, and
vertical directions at the bottom of the HMA over the course of a one year monitoring period.
This study was conducted at the Integrated Road Research Facility (IRRF)’s test road in
Edmonton, Alberta, Canada, which is fully-equipped with structural and environmental
monitoring instruments. Based on the results, noticeable variations for horizontal and vertical
strains at the bottom of the HMA were found, especially during the thaw season. Additionally, a
consistent relationship is established between thermal-induced transverse and horizontal strains.
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