# Sustainable Concrete with Recycled Aggregate from Plastic Waste: Physical-Mechanical Behavior
(2021) found that resistance to sulfate attack decreased slightly when plastic mixture comprising 30% (10% PET, 10% PP, 10% HDPE) was added. The mixtures presented greater absorption of up to 9% for the most unfavorable case [36]. Other RPA studies in recent years that can serve as a basis for understanding the results of the current work are those on electronic waste (e-waste) and PVC waste. On the one hand, e-waste is constantly increasing, causing damage to people's health and the environment [29]. General trends have shown that these types of RPAs, like other more common ones, such as PET, PP, and HDPE, reduce concrete's mechanical properties, limiting its application to non-structural uses [29; 30; 32; 33; 34] without reinforcement from treatments or additions. In this sense, [PERSON] et al. (2022) used 25% RPAs and incorporated 5% nano-graphite platelets (NGPs), reporting gains in mechanical strengths (compression: 13.56%; traction: 15.53%; bending: 31.42%). This was explained by the stacking of the hydration products, which made the paste more massive and thick [30]. Most e-waste studies have incorporated replacement percentages not exceeding 30% [29; 31; 33; 34]. Other properties, such as performance against alternative wetting and drying cycles [29], durability [32], sulfate resistance, and resistivity [34], have been improved with the incorporation of these types of plastic aggregates. Regarding PVC waste, it has been found that substitutions of up to 30% can be used mainly for non-structural applications [27]. Some studies have proposed its use in lightweight concrete [23; 25; 26], while others have proposed its use as structural concrete, provided it is reinforced with additional fibers and treatments [24]. Marginal losses have also been found in mechanical strength (no greater than 8% with substitutions of up to 30% RPA), absorption, and workability [28]. Other authors have reported gains in flexural and abrasion resistance [23; 28]. Likewise, various investigations have explored substituting high percentages of PVC RPA (75%). For example, [PERSON] et al. (2021) added polyvinyl alcohol, which increases the water viscosity in concrete and reduces the desiccation phenomenon [24]. [PERSON] et al. (2023) replaced 100% of natural sand with recycled PVC in combination with glass waste, finding promising properties, such as thermal insulation, but limiting its use as structural concrete [25]. [PERSON] et al. (2015) evaluated coarse and fine aggregates in proportions of less than 70% [26]. [PERSON] et al. (2024) reported increases of up to 10% in flexural strength when replacing up to 10% NA with PVC RPA [23]. Meanwhile, [PERSON] et al. (2019) found that up to 30% coarse PVC RPA can be used without any significant losses in the mechanical properties [28]. Generally, when RPAs are incorporated into concrete, the trend indicates a loss in the overall quality of the most important properties regardless of the plastic used; however, low replacement percentages can provide adequate quality. To reverse the losses in the properties of recycled concrete, some studies have used supplementary cementitious materials and/or additions [41; 42; 43; 44; 45] or gamma or microwave radiation treatments in the aggregates [17; 47] to use them in structural applications. Some of the additions that have been incorporated include nano-silica or silica fume [43; 44; 45], fly ash [45], nano-iron oxide [42], nano-graphite platelets [30], and metakaolin [46], among others. These studies have found that incorporating these additions reverses the initial losses in properties when using RPAs and increases the mechanical, physical, and durability properties [41; 42; 43; 44; 45], suggesting microstructural densification [30; 42]. Other researchers have measured the environmental impacts of incorporating plastic aggregates in concrete. [PERSON] et al. (2021) assessed the potential of climate change in a gate-to-gate life cycle assessment.