Mix design of the composition of general construction concrete based on recycled aggregates

This study's object is the concrete for general construction purposes that includes recycled aggregates formed from the processing and classification of residues from damaged or destroyed concrete buildings and structures, including those affected by military operations. The task addressed relates to the use of recycled concrete aggregates in conventional concrete, including the partial or complete replacement of natural aggregates. This area of research is aimed at devising a framework for the application of recycled concrete aggregates as a secondary raw material for the construction industry. This paper describes the characteristics of recycled concrete aggregates from recycled concrete structures. It was found that these aggregates have significant structural defects such as cracks and pores of various origins. They are also characterized by compositional heterogeneity and an increased content of weak grains, at around 18%. Meanwhile, the content of fine fractions is almost 34%. This naturally worsens the physical and mechanical properties of concrete made with such aggregates. However, a rational approach to using concrete mix components makes it possible to obtain concrete with appropriate performance characteristics, corresponding to class C20/25 (29.2 MPa) with 50% recycled concrete aggregate content. Using this type of aggregate could conserve natural minerals, tackle the issue of disposing of large-tonnage industrial waste, as well as significantly improve the potential for large-scale reconstruction in Ukraine. This may be achieved by accelerating the construction of damaged and destroyed housing stock and by obtaining a substantial raw material resource in the form of recycled aggregate as an alternative to local materials