Environmental impact of recycled aggregate treatment methods using life-cycle assessment and cost analysis

Purpose: The rapid accumulation of construction and demolition waste (CDW) and depletion of natural resources demand sustainable alternatives in concrete production. Recycled aggregates (RA) can mitigate resource depletion and waste generation, yet untreated RA often exhibit poor mechanical and durability properties. Although various treatments improve performance, their environmental and economic implications remain unclear. This study conducts an integrated cradle-to-gate life cycle assessment (LCA) with Module D credits and cost analysis in an Australian context, comparing eight concretes—natural aggregate concrete (NAC), untreated recycled aggregate concrete (RAC), and six treated RAC. All mixes were designed to achieve comparable compressive strength, enabling a strength-standardized comparison linking mechanical equivalence with sustainability and cost. Methods: The LCA was performed in SimaPro 10.2.0.1 using the ALCAS v2.05 method with inventory data from AusLCI 1.45, Ecoinvent 3.11, and regional datasets from Victoria. The mixes varied by aggregate type, including accelerated carbonation, polymer impregnation, pozzolanic coating, bacterial treatment, and nano-material coating. Environmental impacts were evaluated across multiple categories, emphasizing global warming potential (GWP). Module D credits, per EN 15804:2012 + A2, accounted for avoided burdens, while cost analysis assessed economic feasibility. Results and discussion: Carbonated RAC showed the lowest GWP (27% below NAC) and production cost, making it the most sustainable option. Cement-slurry RAC achieved an 11% GWP reduction with competitive cost. All treated RAC matched the control’s strength, confirming that targeted treatments can enhance performance and sustainability. Module D credits highlighted circularity benefits: NAC was negative due to virgin aggregate extraction, whereas all RAC were positive, with carbonation and pozzolanic coatings performing best. Conclusions: By comparing concretes of matched strength, this study demonstrates that appropriate RA treatments can enhance mechanical performance, reduce environmental impact, and lower cost, supporting sustainable concrete practice and improved LCA methodology.