Short-term mechanical properties of concrete containing recycled polypropylene coarse aggregates under ambient and elevated temperature

In recent years, the use of recycled plastic aggregate (RPA) as an alternative aggregate material has been considered to lower the environmental impact of both concrete and waste plastics. Recycled plastic aggregate concrete (RPAC) is now recognized as a highly promising technology that can contribute to resource efficiency in the construction industry. In this paper, the first experimental study on the properties of concretes manufactured using recycled polypropylene (PP) coarse aggregates is presented. Eight batches of concretes were manufactured with different RPA contents. The effect of RPA content on the compressive strength, elastic modulus, flexural strength, splitting tensile strength, workability, and fresh and hardened density of each batch is studied. Although the results illustrate that the mechanical properties of RPACs are lower than those of concretes produced with natural aggregates, when RPA content is below a certain threshold, this difference is not excessive. These results suggest that the method investigated in this study can offer an environmentally sustainable avenue for the use of waste PP. This study is also the first to investigate the compressive behavior of RPACs subjected to temperatures around the melting point of RPAs. The compressive strength of RPACs decreases significantly when exposed to elevated temperatures, with specimens having higher RPA contents experiencing greater reductions.