Framework for a circular economy on precast concrete curbs containing recycled aggregates: mechanical, environmental, and cost viability

Abstract

Precast concrete curbs (PCCs) are crucial for infrastructure, ensuring durability in traffic management and landscaping. This study promotes circular economy (CE) principles by recycling damaged PCCs, reduced to less than 50% of their original volume, into recycled concrete aggregate (RCA) to replace natural aggregate (NA). In addition, it advocates repairing PCCs that retain over 50% of their original size to extend lifespan and minimize waste. Deteriorated PCCs underwent dismantling, segregation, crushing, and grading to produce RCA. Mixes 1D1 and 1D2 use only NA for recycling and repair, respectively. Mixes 2D1, 3D1 (recycling) and 2D2, 3D2 (repair) incorporate 100% coarse RCA, 50% fine RCA, and styrene butadiene rubber (SBR)-to-water ratios of 1:25 for mixes (2D1, 2D2) and 1:50 for mixes (3D1, 3D2), respectively. A cradle-to-cradle approach assessed economic and environmental impacts of 1-m PCC lengths across recycling and repair scenarios. Optimal mechanical outcomes in repair scenarios were achieved for mixes 1D2 and 2D2, resulting in 2.1% increased and 11.5% decreased compressive strength compared to conventional concrete (CC). Mixes 2D2 and 3D2 provided significant environmental benefits, reducing impacts by 38% and 41%, respectively. Life cycle costing (LCC) analysis highlighted highest economic savings with mixes 2D2 and 3D2, offering discounts of 20.0% and 24.0%. These findings endorse CE practices for PCCs while maintaining acceptable mechanical properties.