Life cycle sustainability assessment of fly ash concrete structures

Concrete is one of the most widespread construction materials in the world, but its production is responsible for significant amounts of energy consumption, and even greater greenhouse gas emissions. However, the substitution of Portland cement with fly ash (FA) reduces both the energy consumption and the greenhouse gas emissions generated during the production of clinker. Currently, most studies of FA concrete focus on mechanical properties, sustainability assessments (environment, society and economy) of FA during its life cycle have not been reported. This paper presents a life cycle sustainability assessment (LCSA) that brings together environmental, economic and social impacts using a proposed three-dimensional coordinate diagram to combine the different units into a single sustainable value. The assessment method is applied to different substitutions of FA in concrete to ascertain the optimum substitution percentage across these three factors. Monte Carlo simulation is then used to evaluate the durability of concrete structures with different FA addition in order to calculate their service life. A case study is conducted of a bridge structure with different FA substitutions; this demonstrates that the addition of FA would improve the sustainability of concrete significantly in the short term. However, when the durability and service life of the structure are taken into account, without maintenance, the use of FA concrete may not improve the environment performance due a potentially shortened service life, but it can reduce the social burden and save costs significantly over the long term.