This study aimed to investigate the recycling opportunities for industrial byproducts and their contribution to innovative concrete manufacturing processes. The attention was mainly focused on municipal solid waste incineration fly ash (MSWI-FA) and its employment, after a washing pre-treatment, as the main component in artificially manufactured aggregates containing cement and ground granulated blast furnace slag (GGBFS) in different percentages. The produced aggregates were used to produce lightweight concrete (LWC) containing both artificial aggregates only and artificial aggregates mixed with a relatively small percentage of recycled polyethylene terephthalate (PET) in the sand form. Thereby, the possibility of producing concrete with good mechanical properties and enhanced thermal properties was investigated through effective PET reuse with beneficial impacts on the thermal insulation of structures. Based on the obtained results, the samples containing artificial aggregates had lower compressive strength (up to 30%) but better thermal performance (up to 25%) with respect to the reference sample made from natural aggregates. Moreover, substituting 10% of recycled aggregates with PET led to a greater reduction in resistance while improving the thermal conductivity. This type of concrete could improve the economic and environmental aspects by incorporating industrial wastes—mainly fly ash—thereby lowering the use of cement, which would lead to a reduction in CO2 emissions.
In the last 20 years, there have been a series of seismic events in Italy that have caused serious damage to civil and building structures. This has led to a significant increase in the use of concrete for the reconstruction of new structures and the repair of existing structures damaged by earthquakes. At the same time, the concrete industry is responsible for the most significant environmental damage during the life cycle of the built environment. The environmental disadvantages characterizing the concrete industry are related to the constant growth of the exploitation of natural aggregates. Therefore, it is necessary to use alternative and innovative aggregates that provide good concrete performance and lower environmental impacts. In this study, a very promising route from an environmental point of view is given by the use of artificial aggregates from industrial waste as substitutes for natural aggregates. An innovative low cost and energy saving granulation process has been employed to produce lightweight aggregates using fly ash from the incineration of municipal solid waste and ground granulated blast furnace slag. The final aim of this research is to demonstrate the environmental sustainability of artificial aggregates, through a comparison of three different mixtures.
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