Integrated LCA and LCCA for various compositions and traffic classes of hot mix asphalt and cold in-place recycling pavements in Saudi Arabia

The new development initiatives by the Saudi Arabian government persistently demand new highways, along with the rehabilitation of existing ones. The study conducted Life Cycle Analysis (LCA) and Life Cycle Cost Analysis (LCCA) of 50 [25 hot mix asphalt (HMA) and 25 cold in-place recycling (CIR)] scenarios with combinations of five pavement layers' thicknesses and five traffic classes (TCs) with equivalent single-axle loads (ESALs) from 250,000 to 31,000,000. Compared to equivalent HMA scenarios, CIR exhibited noteworthy reductions in energy (38-59%), economic cost (19-26%), water consumption (17-45%), CO 2 (20-46%), NOx (49-66%), PM10 (~99%), SO 2 (25-50%), CO (29-53%), Hg (up to 44%), Pb (12-41%), and toxicity potential (8-37%) for 'very light' to 'light' TCs (ESALs < 2 million). CIR also showed significant reductions for 'medium' to 'very heavy' TCs (ESALs 7 to 31 million) in energy (38-43%), economic cost (22-27%), water consumption (18-23%), CO 2 (20-26%), NOx (50-54%), PM10 (~99%), SO 2 (26-31%), CO (29-34%), Hg (up to 3-19%), Pb (12-18%), and toxicity potential (15-24%). A sustainability index integrating LCA and LCCA results showed high scores for CIR scenarios with relatively thicker sub-bases (20 cm) and bases (20-25 cm) and thinner CIRs (7 cm) in each TC. Although a low environmental footprint and reduced lifecycle cost make CIR a sustainable rehabilitation option, the decision-makers must consider the associated implications in design, policy-making, quality control, and operational complexities. The study establishes practical guidelines for CIR applications in sustainable pavement rehabilitation projects in Saudi Arabia and elsewhere.