Assessing the environmental impacts of upcycling recycled aggregates into concrete with consideration of resource flows and substitution effects

This study evaluated the properties of concrete incorporating repeatedly recycled aggregates through laboratory experiments. In parallel, it quantitatively analyzed the environmental and economic impacts of repeated recycling of waste concrete, taking into account the policy and infrastructural context of South Korea, where landfilling of construction and demolition waste is virtually prohibited and recycling is mandatory. The analysis considered three recycling scenarios. In the first scenario, waste concrete was recycled as road base material through all three cycles. In the second scenario, it was recycled once as concrete aggregate and once as road base material. In the third scenario, it was recycled twice as concrete aggregate. Environmental impacts were assessed using five indicators, including global warming potential, abiotic depletion potential, ozone depletion, acidification potential and eutrophication potential. Economic feasibility was evaluated based on total material costs. The experimental results showed that concrete containing recycled aggregates maintained similar slump and compressive strength compared to natural aggregate concrete across the two cycles of recycling. However, repeated recycling as concrete aggregate led to increased environmental burdens and higher total costs. This outcome was mainly attributed to the lower recovery rate of recycled coarse aggregate for concrete, which resulted in a larger volume of surplus recycled fine aggregate that required additional processing. Among the three scenarios, the first scenario involving only road base reuse exhibited the most favorable performance in both environmental and economic aspects.