# Analysis of Life Cycle Environmental Impact of Recycled Aggregate
## 1 Introduction  
In South Korea, redevelopment and reconstruction are being actively performed due to the economic and functional service-life expiry of older constructed structures. Such development inevitably generates a rapidly increasing quantity of construction waste. Waste concrete accounts for approximately 60% of the waste produced in redevelopment and reconstruction projects, and is not being effectively recycled despite attempts underway in countries such as the United States and Japan. Technology is currently under development to utilize recycled aggregate, obtained by crushing waste concrete, as a high-value-add material with applications such as aggregate for road construction and concrete. The field application of concrete using recycled aggregate is being performed with slowly increasing frequency in a variety of areas, including road construction.  
The construction industry has been making efforts to become an economically and environmentally sustainable industry, while continuing to face social problems such as an increase in industrial and construction waste and the measures devised to process the waste cause further environmental problems, such as pollution and resource depletion [1].  
Moreover, the use of natural aggregate is gradually decreasing due to changes in environmental awareness and the depletion of resources. The use of crushed stone aggregate and marine sand is increasingly replacing natural aggregate, but these materials also cause various problems, such as ecosystem destruction and transportation-distance challenges [2].  
Recycled aggregates are alternative resources to river or forest aggregates. Their supply proportion is continuously increasing and will continue to play an important role as a recycled resource. If natural aggregates are consumed at the current level without promoting the usage of recycled aggregates at a rate of 30 million tons per year, all natural aggregates are expected to be exhausted in the next 20 years [3].  
However, the process of producing recycled aggregate generates large environmental loads because it requires more processing than the collection of natural aggregate. In addition, the reliability of the quality of recycled aggregate is low, making it most suitable for utilization in landfill or embankments. Studies have been conducted on the quality of recycled aggregate, but there remains a paucity of research on the reduction of the environmental load generated by the production of recycled aggregate. Although the use of recycled aggregate that utilizes construction waste is being recognized as a positive phenomenon in terms of the efficient utilization of resources and the positive environmental aspects, minimizing the environmental loads inevitably generated by aggregate production remains an important issue.  
Accordingly, a number of studies on the emissions and the reduction in the environmental impact of concretes that are mixed with recycled aggregates have been conducted overseas. A quantitative evaluation of concretes mixed with recycled and general aggregates is required to assess the various environmental impact categories (global warming potential (GWP), ozone depletion potential (ODP), photochemical ozone creation potential (POCP), eutrophication potential (EP), acidification potential (AP), and biotic resource depletion potential (ADP)).  
This study assessed the life cycle environmental impact of recycled aggregate using life cycle assessment (LCA). It divided the process into raw materials, transport, and manufacturing of recycled aggregate, and identified the materials used in each stage and energy consumption amount in order to assess environmental impact. The study also compared and analyzed the environmental impact of recycled aggregate with artificial light-weight and slag aggregate.