Impact of extended storage and transportation on the performance and workability of high-content rubber-modified asphalt

This study evaluated the performance of high-content rubber-modified asphalt (HCRMA) under extended curing conditions during storage and transportation. Asphalt binders with rubber contents of 18%, 22% and 26% were cured in an oven at 185 °C for up to 47 h after blending. Laboratory tests were conducted to evaluate the workability, rheological behaviour, storage stability and microstructural characteristics of the samples. HCRMA exhibited improved workability with prolonged curing, with the initially high rotational viscosity (>4 Pa·s) decreasing and stabilising after approximately 36 h. HCRMA binders after 1 h of shear mixing exhibited improved high-temperature performance grades (>PG 82) and decreased moderately to around PG 70 after extended curing. The low-temperature PG improved from PG -28 for the neat asphalt to PG -34 to -40 for HCRMA and did not degrade significantly with extended curing. The 18% and 22% HCRMA showed better storage stability than the 26% HCRMA. Mechanistic-empirical analysis indicated decreased thermal cracking but increased rutting for mixtures incorporating HCRMA, which could be attributed to the lower stiffness and more viscous behaviour. Microstructural analyses indicate that extended curing mainly promotes rubber swelling and dispersion, with limited ageing or chemical reactions.