The increasing interest in recycled aggregates as an alternative to natural resources has generated a rapidly expanding body of scientific literature; however, the global evolution, intellectual structure, and emerging research directions of this field require comprehensive assessment. This study ana-lyzes two decades of research on recycled aggregates in concrete through a bibliometric and sci-ence-mapping approach. Bibliographic records indexed in Scopus between 2006 and 2025 were retrieved using the search terms “recycled aggregate” and “concrete” and analyzed using Biblio-metrix/Biblioshiny and VOSviewer. A total of 14,044 documents from 1,513 sources were identified, showing an annual growth rate of 19.51%, with publications increasing from 74 in 2006 to 2,189 in 2025. China emerged as the leading country in scientific production, while Tongji University was the most productive institution. Keyword co-occurrence analysis revealed three major conceptual domains associated with recycled aggregate utilization, mechanical performance and durability, and sustainability and environmental impact. Thematic evolution showed a progressive transition from research focused primarily on compressive strength and technical feasibility toward more integrated approaches involving durability, microstructure, sustainable development, and waste utilization. Recent topics such as machine learning, forecasting, carbon sequestration, and geo-polymer concrete indicate an emerging shift toward predictive tools and decarbonization-oriented strategies. Overall, the findings demonstrate that recycled aggregate concrete research has evolved from establishing technical feasibility toward optimizing material performance, environmental benefits, and advanced predictive assessment.

Concrete is the most widely used material in global construction, which generates high demand for natural resources and a significant carbon footprint. In response to these challenges, incorporating plastic waste, such as high-density polyethylene (HDPE), has been proposed as a sustainable alternative to reduce dependence on natural aggregates and mitigate plastic pollution. This study evaluates the mechanical performance of concrete with partial replacements of HDPE at 2.5%, 5%, 7.5%, 10%, 15%, 20%, and 30% in sand to produce HDPE-concrete, which is compared against a control mix with 0% replacement. Optimal replacement percentages have been identified in the literature, and 64 specimens were prepared and tested to determine the concrete's behavior, including its strength and flexural performance, to validate the advantages and disadvantages of each replacement in the search for the optimal configuration of sustainable concrete. Results showed that 5% and 7.5% replacement levels achieved optimal compressive (409 kg/cm²) and flexural (49 kg/cm²) strengths, respectively. Although these mixes exhibit slower strength gain reaching peak values at 28 days, lower replacement rates showed superior 7-day strength. Conversely, higher replacement levels increased recycling volume, reduced unit weight and slump, and raised air content without compromising the paste-aggregate bond. The findings suggest that HDPE-concrete is a promising solution for the construction industry, as it not only promotes the circular economy of plastic waste but also offers adequate mechanical performance, making it a viable and eco-friendly alternative for building material production.