# Sustainable Concrete with Recycled Aggregate from Plastic Waste: Physical-Mechanical Behavior
Their study suggests that using up to 25% aggregate can generate environmental gains while maintaining the same compressive strength [48]. In this sense, it is necessary to continue exploring the environmental impacts in scenarios considering all life cycle stages, including stage D, i.e., the benefits and loads after the system's life cycle has ended. Although research on RPA has been previously conducted, it is necessary to continue looking for alternatives using different types of plastics and new thermal treatments, expanding durability studies, and performing life cycle assessments, among other tests [40; 49], especially in countries such as Mexico, where structural regulations are limited regarding the use of recycled materials. Furthermore, it should be noted that the most studied plastic to date is PET. In this sense, the current work seeks to explore additional alternatives that are usually off the radar and have not been reported in the literature, such as thermoplastic paint residues used in paving, which come from horizontal signage procedures and do not comply with current regulations due to their color or consistency. Much of the contribution of this research to the current knowledge lies in the above since, according to the Scopus database, only thermoplastic paint and its relationship with concrete are mentioned in the work of [PERSON] and [PERSON] (2024) [50], where it is not discussed as a recycled aggregate that is part of a concrete mix but as part of the LCA carried out on road construction projects in India. In addition to the above, further research is needed to achieve homogenous results to create regulations for the regulated use of RPAs. The Mexican complementary technical standard for the design and construction of concrete structures [51] establishes that only recycled aggregates from construction and demolition waste can be used in their coarse fraction and limits them to a maximum substitution of 20% for use in structural concrete. The use of fine aggregate is not permitted. On the other hand, polymeric fibers, such as PP, HDPE, acrylic, nylon, or polyester, are permitted for non-structural use in compliance with ASTM D7508D/7508M regulations [51]. In other words, more research is needed to support the use of fine aggregates and widen the permissible percentages of substitution using coarse aggregates and fibers. In order to address this problem, which would allow for a reduction in the extraction of raw materials and their associated impacts, as well as the reincorporation of urban solid waste and construction and demolition waste, which tend to have limited reuse and/or recycling rates in the Mexican context, the objective of this work is to evaluate the physical and mechanical properties of concrete that incorporate recycled aggregates from two plastics with different natures. First, four mixtures were made, where natural gravel was replaced by recycled gravel from thermoplastic paint (TP) residues used for horizontal paving, in percentages of 5%, 10%, 15%, and 20%. Then, three mixtures of recycled PET sand were made with replacement percentages of 5%, 9%, and 14% to support the use of sand in structural concrete and vary the percentages used in studies previously reported in the literature. Both types of mixture were compared with a reference mixture.