Infra Structures has a variety of social, economic and environmental impacts through long period of time. Life Cycle Assessment has been applied to assess holistic aspects and improvement alternatives of precast concrete bridge and steel bridge.
Basic framework utilized was 4 I's, which are initiation, inventory analysis, impact assessment and improvement assessment. After screening according to data completeness, electricity, coal, oil, fuel gas consumption, $CO_2$, CO, SOx, NOx, hydrocarbon and solid waste were selected for impact assessment. To consider economy and locality, normalization with energy prices and pollutants reduction cost of each geographical location was applied to each item of environmental burden before impact assessment. Accumulation of impacts through time, and improvement alternatives of each bridge were investigated in the improvement assessment.
For both of steel and concrete bridges, primary product production such as steel roll and cement manufacturing was the major stage with the most resource consumption and with the highest impacts, followed by the construction and demolition stage. Increment of environmental impacts of steel bridges, with period of use, was much less than concrete bridges, due to their longer life span.
Best improvement alternatives were recycling of waste structural steels in the vicinity for steel bridges, and increasing recycling ratio of waste concrete for concrete bridges.
In performing LCA on huge structures such as bridge, the pollutants from heavy equipments for construction and demolition stages which have considerable portion of overall results, the cumulated impacts to compare other subject with different life span, and the recycling of high value-added materials should be considered.
