Comparative Assessment of Alternative Fine Aggregates for Sustainable Concrete: Physical, Chemical, and Mechanical Characterization of Sri Lankan Sands

Abstract

Excessive river sand extraction in Sri Lanka has depleted over 40% of alluvial reserves in major basins (2010-2023), necessitating urgent identification of sustainable alternatives. This study systematically evaluated four geographically distinct sand types, river (Polonnaruwa), sea (Muthurajawela), dune (Kandakuliya), and estuary (Kalutara) through integrated physical, chemical, and mechanical characterization. Sieve analysis, chloride determination (Volhard’s method), and strength testing at 7 and 28 days were conducted. River and dune sands achieved compressive strengths above 30 MPa with low chloride content (<500 mg/kg), meeting international standards for structural concrete. Sea sand exceeded chloride limits (1,796 mg/kg; 259% higher) but showed potential if treated. Estuary sand reached 29.3 MPa with borderline chloride levels, limiting its use. Failure analysis indicated good structural performance with river and dune sand, while sea and estuary sands showed brittle modes. Overall, processed dune sand and treated sea sand offer viable replacements for river sand, supporting sustainability. Successful implementation requires chloride regulation and investment in treatment technologies.