Strength and Durability Characteristics of Sustainable Pavement Base Course Stabilized with Cement Bypass Dust and Spent Fluid Catalytic Cracking Catalyst

This study explores the potential of a composite binder comprising cement bypass dust (CBD) and spent fluid catalytic cracking (FCC) catalyst for sustainable pavement base stabilization. Various CBD/FCC ratios (30:70, 50:50, 70:30) and binder contents (4%, 6%, 8%, 10%) were evaluated through laboratory testing. The 50:50 CBD/FCC mixture demonstrated optimal performance, achieving an unconfined compressive strength (UCS) of 15.6 MPa at 28 days with 10% binder content. The mix exhibited improved stiffness (E50 modulus up to 13,922 MPa) and resistance to degradation under wetting–drying cycles, attributable to synergistic cementitious and pozzolanic reactions. Microstructural analysis revealed a denser matrix, validating the enhanced performance. These findings suggest CBD and FCC, as promising materials for sustainable pavement construction, align with circular economy principles.