Performance Studies On Stone Mastic Asphalt Mixes with Reclaimed Asphalt Pavement

Stone Mastic Asphalt (SMA) is a high-performance gap-graded bituminous mix widely recognized for its superior rutting resistance, durability, and long-term serviceability. However, its higher binder content and the need for stabilizing fibers make it costlier than conventional mixes, prompting the exploration of sustainable and economical alternatives. Reclaimed Asphalt Pavement (RAP), generated through pavement milling operations, offers an effective substitute for virgin aggregates and binder, reducing construction costs, conserving natural resources, and minimizing environmental burdens associated with waste disposal. This study evaluates the performance of SMA mixes incorporating RAP at varying replacement levels using two binder types—VG 30 and CRMB 55—along with 0.3% cellulose fiber as a stabilizing additive. The research program includes material characterization, Marshall mix design, drain-down assessment, Cantabro abrasion, moisture susceptibility analysis through Indirect Tensile Strength (ITS) and Tensile Strength Ratio (TSR), permanent deformation (rutting), fatigue performance, resilient modulus testing, and rheological evaluation of binders using Dynamic Shear Rheometer (DSR). RAP-modified SMA mixes were prepared with RAP contents ranging from 10% to 60%. Results indicate that all materials, including RAP-derived binder, satisfy MoRTH specifications. SMA mixes with CRMB 55 exhibited higher stability, durability, and moisture resistance compared to those with VG 30. RAP incorporation increased mix stiffness and stability, with optimum performance achieved at 40% RAP for VG 30 and 50% RAP for CRMB 55. TSR values for these optimum RAP levels met the IRC: SP:079 requirement of >85%. Although durability decreased slightly with increasing RAP due to the aged nature of the material, all optimum mixes remained within permissible limits. Rheological studies confirmed improved high-temperature performance with modified binders. Overall, the study demonstrates that RAP-modified SMA mixes can effectively replace conventional mixes for heavy-traffic pavements while offering economic and environmental advantages without compromising performance.