Radiation-thermal-moisture coupling effects on viscoelasticity properties of reclaimed asphalt rejuvenated by rubberized asphalt

In high-temperature regions, incorporating crumb rubber (CR) and reclaimed asphalt pavement (RAP) into flexible pavement enhances rutting resistance and elastic recoverability. However, high temperature, intense radiation, and humidity can accelerate asphalt ageing. This study investigated the variations in viscoelasticity of asphalt mixtures subjected to a radiation-thermal-moisture coupling environment and examined the impact of CR and RAP. Laboratory tests used two virgin binders, two CR contents, two RAP sources, and two RAP contents to produce 12 different asphalt mixtures with controlled aggregate gradation. A self-developed Xenon accelerated ageing chamber was used to simulate ageing, with 7 days of accelerated ageing equating to 1 year of natural ageing, achieving four ageing states: 0, 7, 14, and 21 days. Dynamic modulus tests were conducted at 5 degrees C, 20 degrees C, 35 degrees C and 50 degrees C and frequencies of 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz and 25 Hz. Master curves of dynamic modulus, phase angle, storage modulus, and loss modulus were constructed for each asphalt mixture at all ageing states. Parameters such as the Glover-Rowe parameter, Viscoelastic Cracking Index, dynamic modulus master curve shape parameter -beta/gamma, and phase angle master curve shape parameters a and c were analyzed. The results indicated that the dynamic modulus at high frequencies might decrease after 21 days of accelerated ageing. Strong correlations were found between the Glover-Rowe parameter, Viscoelastic Cracking Index, and master curve shape parameters, especially between c and other parameters. CR significantly increased ageing sensitivity under low frequency and high temperature conditions, while RAP reduced the viscoelasticity variation caused by accelerated ageing.