Long-Term Aging of Crumb Rubber-Modified Bitumen: Contrasting the Effectiveness of Standard and Field-Based Extended Aging Procedures through Chemical and Rheological Characterization

This case study investigates the long-Term aging behavior of crumb rubber-modified bitumen (CRMB) under standard and extended aging conditions. Despite CRMB's known benefits, its response to extended aging remains unclear. We compared standard and extended laboratory aging protocols, with the latter designed to better reflect real-world pavement temperatures. The research examined CRMB's aging response considering crumb rubber gradation and blending time (30 min and 90 min) through chemical and rheological tests. Results indicate that CRMB's enhanced performance stems from its composition and potential antioxidant effects. The aging level significantly influenced parameters such as Glover-Rowe (G-R), crossover modulus (Gc*), crossover frequency (ωc), fatigue life (Nf), and oxidation indices (IS=O, IC=O) between rolling thin-film oven (RTFO) and both pressure aging vessel (PAV) procedures. However, the variable blending time showed no significant impact. Notably, standard and extended PAV aging yielded similar results for most parameters, with only IS=O showing sensitivity to the aging level. These findings suggest that the current standard PAV aging procedure adequately simulates long-Term in-service aging of CRMB, making extended PAV aging unnecessary for laboratory evaluation.