Validation of Internal-Restraint Damage Mechanism in Asphalt Mixtures Using Thermal Conditioning and Mechanical Testing

Thermal distresses like transverse and block cracking continue to be major failure mechanisms in asphalt pavements, especially in cold climates. Although external-restraint damage mechanisms have been well studied, the internal-restraint damage mechanism (IRDM), caused by differential thermal contraction between asphalt mastics and the aggregate skeleton, needs more research for full understanding. This study focuses on investigating the IRDM by subjecting asphalt mixture specimens to extreme cooling and evaluating their response using the Ohio CTE (Coefficient of Thermal Expansion) Device and dynamic modulus testing. The Ohio CTE Device test was performed first to monitor thermally induced strain during a controlled cooling cycle from 20°C to −65°C at a rate of 20°C/h. The transition point, captured as the critical cracking temperature, reflected the onset of damage resulting from internal restraint caused by differential thermal contraction between binder and aggregate. To validate this observed transition behavior, dynamic modulus tests were conducted at 0°C on the same specimens before and after thermal conditioning. This temperature was selected to minimize healing effects. Results showed a consistent decrease in |E*| and an increase in phase angle after cooling across all mixtures, with the most significant changes observed at low frequencies. The outcome suggests that finer gradation and the absence of reclaimed asphalt pavement (RAP) tend to enhance low-temperature performance, whereas higher RAP content and coarser gradations increase vulnerability to thermal cracking. The study provides strong mechanical evidence of IRDM effects and validates the Ohio CTE Device’s ability to capture internal damage in asphalt mixtures.