Recycled and Waste Materials in Sustainable Concrete: A Critical Review of Environmental Benefits, Engineering Performance, Challenges, and Future Directions

Abstract

Background: Sudden Infant Death Syndrome (SIDS) and Sudden Unexplained Infant Deaths The rapid growth of infrastructure and urban development has resulted in increasing consumption of natural resources and generation of large quantities of construction, industrial, agricultural, and municipal waste. The incorporation of waste and recycled materials into concrete has therefore emerged as a promising approach for reducing the environmental impacts of conventional concrete and promoting sustainable and circular construction practices. This review critically examines the utilization of recycled concrete aggregates, industrial by-products, agricultural ashes, waste glass, plastic waste, rubber waste, and quarry waste as partial replacements for conventional concrete constituents. The review evaluates their influence on the fresh properties, mechanical performance, durability, environmental impact, and overall sustainability of concrete. The available literature indicates that recycled materials can reduce the consumption of natural aggregates and Portland cement, minimize waste disposal, conserve natural resources, and potentially reduce embodied carbon and energy consumption. However, their incorporation may also introduce challenges, including reduced workability, increased water absorption, weaker interfacial bonding, lower strength and stiffness at high replacement levels, delayed strength development, alkali–silica reaction, and considerable variability in material quality. The review further highlights that the environmental advantages of recycled concrete cannot be assessed solely on the basis of replacement percentages; transportation, processing energy, material quality, durability, service life, and end-of-life recycling must also be considered through life-cycle assessment. Significant research gaps remain in the combined use of multiple waste materials, long-term durability, full-scale structural validation, standardized characterization, and integrated performance–environmental assessment. Future research should focus on multi-waste concrete, life-cycle-based optimization, artificial intelligence-assisted mix design, and multi-objective assessment integrating strength, durability, cost, embodied carbon, and resource efficiency. Such developments can support the transition toward low-carbon, durable, resource-efficient, and circular concrete for sustainable construction.