Cement replacement and recycled aggregates for a more sustainable concrete: experimental investigation and conceptual modelling

A sustainable development policy is clearly not only a desirable objective, but also a necessary attitude in every field, also in buildings technology and structural engineering. In fact, the global need to both minimize the exploitation of natural resources and reduce CO2 emissions, pushes construction industry in adopting new eco-friendly technologies.
This study aims to show the most recent and interesting results achieved in concrete production by using recycling materials, which otherwise would be considered special waste to dispose. Particularly, the attention is focused on both recycled concrete aggregates (RCA) obtained from C&D waste and the use of fly ash (FA), which is one of the residues generated during the combustion of coal.
In recent years, most of the industrialized countries concentrated their attention on this issue, and they are still improving efforts about green policies. Thus, several standards and regulation have been formulated about recycled aggregate concrete and many experimental researches were carried out in order to investigate its performance and applications. So the present study firstly summarizes the regulatory environment about RCA and FA, then it shows the state of art on recycled aggregate concrete (RAC) performance. Moreover it reports an interesting case study, which represents the core aspect. In fact, it is described the experimental campaign carried out by the Civil Engineering Department of the University of Salerno (Italy), assessing the performance of recycled aggregate concrete combined with fly ash (RAC+FA). In that respect, experimental results about fresh and hardened concrete properties are showed, highlighting how they differ from an ordinary concrete, obtained from virgin aggregates and Portland cement. These results finally allow both to establish what are possible applications and to provide technical information for further investigations.