Effect of transportation distance, energy mix and allocation of fly ash on the life-cycle assessment of concrete

Industrial by-products (ex. fly ash, slag) have been used as supplementary cementing materials (SCM) resulting in several benefits, including lowering the environmental impact of concrete. North America is a large cement consumer as well as producer of fly ash from coal-fired power plants. The distance that the fly ash has to travel, the energy grid mixture used in its processing and the allocation of the SCM affect its environmental impact. A comparative life-cycle assessment (LCA) of concrete containing fly ash was carried out and sensitivity analysis of the transportation, energy mix and allocation are conducted in order to ascertain the viability of competing options. The environmental effect of the concrete was measured using four impact categories, namely; Global Warming, Acidification, Water Depletion and Resource Depletion. These categories were combined into a single factor, the environmental efficiency indicator (EEI). This indicator will be used to compare the different mix designs in order for conclusions to be drawn concerning the sensitivity of analysis for fly ash.