Transportation matters - Does it? GIS-based comparative environmental assessment of concrete mixes with cement, fly ash, natural and recycled aggregates

摘要

The urban world is expanding and densifying fast. This requires and produces huge amounts of new construction materials and construction and demolition waste (CDW) every year. Concrete is not only the most important construction material in terms of sheer amount but also regarding embodied greenhouse gas emissions. Alternative concrete mixes have been developed by introducing supplementary cementitious materials (e.g. fly ash (FA)) and CDW (e.g. recycled aggregates (RA)). So far, environmental assessments focus mostly on the production of concrete mixes without considering the transportation-related impacts. This paper appraises the importance of transportation-related impacts of raw materials for concrete production and proposes a new method combining Life Cycle Assessment and geospatial analysis of road transportation of materials. Environmental impacts (EI) of different mixes are assessed for the specific locations of concrete plants. Traditional and alternative concrete mixes are compared to choose site-specifically the mix with lower impacts. For that purpose, two Portuguese cities were considered as case studies. The new method uncovers if and how location of supply and demand for concrete production is important. The results show that for traditional concrete and for mixes incorporating low FA ratio and/or RA, transportation does not matter. However, it matters when choosing between already drastically improved mixes: then, distances from raw materials suppliers to concrete plants can tip the scales of total EI In fact, the distances to FA and recycling plants influence the selection of the most environmental friendly concrete mix. The method can be applied to other case studies and materials.