Life Cycle Assessment of Aggregate Quarry By-Product Fines in Pavement Applications

Quarry by-products (QB) pose a major environmental challenge for quarries as they accumulate in large quantities, and their beneficial uses are continually sought out. Research at the Illinois Center for Transportation introduced seven applications to utilize QB in chemically stabilized base/subbase pavement layers. These applications were evaluated for field performance through accelerated pavement testing. This paper presents results for the environmental benefits and trade-offs of including QB or blends of QB with recycled materials in pavements. The seven QB applications and a control section were evaluated in terms of environmental impacts using life cycle assessment (LCA). The LCA was conducted in accordance with the International Standard Organization ISO 14044:2006 guidelines. The life cycle impacts were calculated in terms of energy consumption and global warming potential. Three scenarios for (1) as-constructed thicknesses, (2) as-designed thicknesses, and (3) thinner sections for local roads were considered. LCA analysis results were interpreted in terms of the normalized impacts and the response benefits based on falling weight deflectometer resilient deflections to reflect on the impacts due to relative service life expectancy. It was shown that cement-stabilized QB pavement layers, particularly those having QB blended with recycled pavement materials, can have lower environmental impacts when normalized over pavement life and anticipated traffic (i.e., when pavement life expectancy is considered).