Circular Economy Potential of Construction and Agricultural Waste Streams in Sri Lanka: A PRISMA-Based Systematic Review of Recycled Aggregate Concrete and Coconut-Shell Biochar

Abstract

The transition from a linear to a circular economy is essential for addressing resource depletion, construction and demolition (C&D) waste generation, and agricultural biomass disposal in the construction industry. Sri Lanka faces growing challenges associated with rapid infrastructure development and the underutilization of waste resources, particularly recycled concrete waste and coconut shell residues. Although recycled aggregate concrete (RAC) and agricultural waste-derived biochar have been widely investigated as sustainable construction materials, their integrated application within a circular economy framework remains limited.

The review specifically focuses on two selected waste- resource pathways: the recovery of C&D concrete waste

as recycled aggregate for concrete production and the valorisation of coconut-shell waste as biochar for incorporation into recycled aggregate concrete. This study presents a PRISMA-based systematic literature review evaluating the circular economy potential of construction and agricultural waste through the utilization of recycled aggregate concrete and coconut shell biochar (CSB). Peer-reviewed journal articles and conference papers published between 2011 and 2026 were identified from major scientific databases and synthesized using thematic analysis following PRISMA screening and eligibility assessment. The review indicates that recycled aggregates reduce dependence on virgin construction materials while supporting effective C&D waste management. Coconut shell biochar enhances the mechanical properties, durability, microstructural performance, and alkali– silica reaction resistance of recycled aggregate concrete. The review also highlights Sri Lanka's Construction and Concrete Waste Recycling Centre as a significant step towards circular construction. Based on the synthesized evidence, this study proposes a Construction–Agriculture Circular Resource Loop Framework that integrates construction and agricultural waste into a unified circular economy model for sustainable infrastructure development in Sri Lanka. The framework provides practical guidance for policymakers, researchers, and industry to advance resource circularity through integrated waste valorisation strategies.