Environmental impacts of three waste concrete recycling strategies for prefabricated components through comparative life cycle assessment

The viability of using recycled coarse aggregate (RA) and demolished concrete lumps (DCLs) in manufacturing concrete products have been demonstrated in previous studies and practical applications but their environmental impacts have not been compared. In this study, we conducted a life cycle assessment (LCA) on prefabricated components made from three recycling strategies, including the recycled aggregate concrete (RAC) strategy (only using RA), the recycled lump concrete (RLC) strategy (only using DCLs), and the recycled lump/aggregate concrete (RLAC) strategy (simultaneously using DCLs and RA). To identify the environmental impacts of these strategies, twenty-four designed scenarios were investigated with a varying RA replacement ratio (0%, 30%, 50%, and 70%), a changing DCL replacement ratio (0%, 20%, and 30%), and two targeted compressive strength of structural component (25 MPa and 35 MPa). An artificial neural network was implemented to estimate the raw materials consumption of those 24 scenarios. In our LCA, the environmental impacts were evaluated through four indicators. The numerical results show that the RLC and RLAC strategies exhibit a relatively lower environmental burden than the RAC strategy among all scenarios due to the utilization of DCLs. Sensitivity analysis also proved that the location of the recycling plant is a critical factor in the selection of the recycling strategy for an optimal environmental benefit. Our study confirmed the advantage of simultaneously using DCLs and RA in the design and fabrication of recycled concrete products from an environmental perspective, paving the way to further exploit the RLAC product as an alternative solution for a sustainable built environment in the near future.

Automated summary

This study conducted a life cycle assessment on prefabricated components made from three recycling strategies, finding that the RLAC strategy of simultaneously using DCLs and RA has a lower environmental burden compared to the RAC strategy. The location of the recycling plant was identified as a critical factor in selecting the optimal recycling strategy for environmental benefit.