To reduce the environmental loads of construction projects, a methodology needs to be established that reasonably assesses the environmental impact. Currently, life cycle assessment (LCA) is used as a methodology for evaluation of the environmental impact in various fields. However, this approach is not employed for the assessment of the environmental impact at the planning or design stages of construction projects. The reason is that the features of construction projects cannot entirely provide the full information required for performing LCA until the design has been complete. This study performed LCA of concrete girders and estimated the properties and basic unit quantity of the environmental loads. Our findings support that environmental impact assessment based on LCA should be performed at the planning or design stage when no full information is still available. Moreover, we propose an environmental impact index based on the input cost and the occurrence rate of environmental loads as an environmental performance indicator of concrete girders. This methodology is expected to induce the paradigm to transit from the existing environmental impact assessment methodology based on input resource amounts to the environmental impact assessment methodology in economic perspective considering the characteristics of construction projects.
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