Environmental and economic assessments of novel polyurethane prepolymer modified porous asphalt: A case study in Hong Kong

Porous asphalt (PA) has gained increasing attention in pavement engineering due to its benefits in stormwater management and traffic noise reduction. However, its open-graded structure generally results in lower durability and a shorter service life compared to dense-graded asphalt mixtures. Recent research show that modification with polyurethane prepolymer (PUP) can effectively improve the durability and longevity of PA. Despite these technical advantages, quantitative assessments of its environmental and economic impacts are lacking. To address this research gap, this study investigates PUP-modified PA (PU-PA) as a sustainable alternative to conventional styrene-butadiene-styrene-modified PA (SBS-PA) using a life cycle perspective. Initial production and construction costs, along with associated greenhouse gas emissions, were quantified and comparatively analyzed for both materials. A life cycle assessment (LCA) and life cycle cost assessment (LCCA) were then conducted to evaluate the environmental and economic performance of PU-PA. Furthermore, sensitivity analysis was performed to identify critical factors influencing its economic feasibility. Results indicate that, despite slightly increased initial costs and emissions, PU-PA offers significant life cycle economic and environmental benefits due to its enhanced mechanical properties and extended service life. Sensitivity analysis identified three critical factors affecting the economic viability of PU-PA: service life, PUP content, and PUP cost. The findings of this study support the feasibility of adopting PU-PA as an innovative and sustainable paving material over conventional modified porous asphalt.