Potential use of municipal solid waste incineration bottom ash as supplementary cementitious materials based on particle size fraction

Abstract Incinerator bottom ash (IBA) is a heterogeneous by-product mainly composed of mineral phases. Despite its variable composition, it is generally classified as a silica-rich secondary raw material, containing significant amounts of aluminium, calcium, and amorphous phases. These characteristics make IBA a potential candidate for use as a supplementary cementitious material (SCM) in blended cement formulations. However, due to its heterogeneity, evaluating the behaviour of different particle size fractions is essential to ensure consistent performance. In this study, the pozzolanic activity of various IBA fractions was assessed using three standard reactivity tests: the modified Chapelle test, the modified R 3 test, and the strength activity index (SAI). The results varied depending on the test applied, but a general trend was observed in which coarser fractions exhibited greater pozzolanic activity than finer ones. The fraction larger than 8 mm consistently showed the best performance across all tests. Additionally, the environmental impact of each fraction was analysed through batch leaching tests to determine the potential release of metal(loid)s. Regarding environmental safety, leaching results confirmed that all particle size fractions met the requirements to be classified as non-hazardous at the end of their life cycle. These findings support the use of IBA, particularly its coarser fractions, as a sustainable and safe SCM in the production of blended cement.