A comprehensive assessment of green concrete incorporated with municipal solid waste incineration bottom: Experiments and life cycle assessment (LCA)

Abstract

To reduce the high carbon emissions in the concrete field and facilitate the sustainable development of concrete, in this study, we repurposed high-volume municipal solid waste incineration bottom ash (MSWIBA) as a supplementary cementitious materials (SCMs) for the production of concrete at different percentages (0%, 10%, 20%, 30%, 40%, 50% and 60%). The influence of MSWIBA on the compressive strength, hydration, microstructure and heavy metal leaching behaviour of concrete was investigated. The results showed that a high volume of MSWIBA will reduce the compressive strength (from 56.81 MPa to 12.65 MPa) because aluminium produces hydrogen in an alkaline environment and excessive incorporation of MSWIBA leads to insufficient active substances. The content of ettringites and calcium silicate hydrate (C-S-H) initially increases (from 0.286 ％ to 0.405 ％ and from 0.635 ％ to 0.893 ％) and subsequently decreases (from 0.405 ％ to 0.275 ％ and from 0.893 ％ to 0.500 ％) as the proportion of MSWIBA in the mixture gradually increases due to the aluminium salt content reacting with the sulfate and pozzolanic reactivity of MSWIBA. In addition, compared with those in MSWIBA, the amounts of leachable hazardous ions (Cu, Pb, Cr, As and Hg) in concrete were effectively reduced by 87.1%, 83.3%, 70.0%, 90.3%, and 89.3%, respectively. Additionally, the measured heavy metal leaching met Chinese specification requirements. Life cycle assessment (LCA) was employed to evaluate environmental impacts (EIs), and it was found that using MSWIBA as a SCM can reduce the EI by 7.5 ％− 44.1 ％ (from 2.58E-11 to 1.56E-11) when the replacement cement ratio of MSWIBA is from 10 ％ to 60 ％. By normalizing the EI indices, it was found that the global warming potential (GWP) and eutrophication potential (EP) were the main contributors to the EI. Finally, a model was established to assess the comprehensive performance, including the environmental impact, compressive strength, porosity, apparent density, and ecology-strength efficiency, of the different MSWIBA formulations, and the comprehensive performance improved when the MSWIBA percentage was 30%.