Evaluation of environmental impact distribution methods for supplementary cementitious materials

As the world's most widely used construction material, the production of concrete has been recognized to lead to major environmental impacts. To promote sustainability in the concrete industry, various kinds of supplementary cementitious materials (SCMs), such as fly ash, blast furnace slag and silica fume have been used to replace cement in concrete production. The nature of these SCMs has therefore been changed from wastes to co-products or by-products. Life cycle assessment (LCA) has been increasingly adopted in the concrete industry to assess environmental sustainability. However, the choice of an appropriate method for impact distribution in the LCA of concrete incorporating SCMs is a research challenge. This study aimed to present a comprehensive review of the impact allocation approaches for assessing the environmental impacts of SCMs-incorporated concrete. Furthermore, the use of the system expansion approach was compared with the conventional mass and economic allocation approaches. A case study of concrete production using SCMs in Hong Kong was conducted using the different approaches. The results were then analyzed and it was concluded that the system expansion approach is appropriate for the assessment of the environmental impacts of SCMs-incorporated concrete.