Replacing Fine Aggregates with Sustainable Recycled Waste

Abstract

The excessive extraction of natural river sand as the predominant fine aggregate in concrete construction has led to severe environmental degradation, including riverbed erosion, loss of aquatic habitats, and depletion of a finite natural resource. Simultaneously, the accelerating generation of industrial and municipal solid waste creates mounting pressures on land disposal capacity and environmental quality. This paper investigates the feasibility and structural implications of partially or fully replacing natural fine aggregates in concrete mixes with sustainable recycled waste materials, including Manufactured Sand (M-Sand), Quarry Dust (QD), Bottom Ash (BA), Recycled Concrete Fine Aggregate (RCFA), Crumb Rubber (CR), Foundry Sand (FS), and Glass Powder (GP). A comprehensive experimental programme was conducted involving the preparation of M25 and M30 grade concrete specimens with replacement levels of 10%, 20%, 30%, 50%, and 100% by weight of natural fine aggregate (NFA). Fresh concrete properties were assessed through workability tests, while hardened concrete properties were evaluated through compressive strength tests at 7, 14, and 28 days, split tensile strength, and flexural strength. Results indicate that replacement levels of 20–30% with M-Sand and Quarry Dust yield compressive strengths equivalent to or exceeding those of control mixes, while higher replacement levels with Bottom Ash and Crumb Rubber result in moderate strength reductions that may still be acceptable for specific structural applications. The findings confirm that strategic utilisation of recycled waste materials as fine aggregate replacements presents a technically viable, economically advantageous, and environmentally responsible pathway toward sustainable concrete construction.

Introduction

This study investigates the use of recycled and industrial waste materials as sustainable replacements for natural river sand in concrete. River sand, which makes up about 30–35% of concrete volume, is becoming scarce due to excessive mining, causing environmental degradation such as riverbed erosion, reduced groundwater recharge, and biodiversity loss. To address this issue, the research evaluates alternative fine aggregates including Manufactured Sand (M-Sand), Quarry Dust (QD), Bottom Ash (BA), Recycled Concrete Fine Aggregate (RCFA), Crumb Rubber (CR), Foundry Sand (FS), and Glass Powder (GP).

An experimental program was conducted using M25 and M30 concrete mixes with replacement levels ranging from 10% to 100%. Fresh concrete was tested for workability, while hardened concrete was evaluated for compressive, split tensile, and flexural strengths at 7, 14, and 28 days.

Key Findings

• M-Sand proved to be the best alternative, achieving compressive strengths higher than conventional concrete at 20–30% replacement and remaining suitable even at 100% replacement.
• Quarry Dust improved strength up to 20–30% replacement but reduced workability because of its fine, angular particles.
• Bottom Ash performed satisfactorily up to 20% replacement, though higher percentages significantly reduced strength due to its porous structure.
• RCFA showed acceptable performance up to 30% replacement, with higher levels increasing porosity and lowering durability.
• Crumb Rubber greatly reduced compressive strength but enhanced ductility, impact resistance, and energy absorption, making it suitable mainly for non-structural applications.
• Foundry Sand and Glass Powder performed well at 20–25% replacement, with Glass Powder providing additional long-term strength through pozzolanic reactions.

Environmental and Economic Benefits

Using recycled fine aggregates reduces dependence on river sand, diverts industrial and construction waste from landfills, lowers environmental impacts, and decreases material costs by utilizing locally available waste products.

Optimal Replacement Levels

• M-Sand: Up to 100%
• Quarry Dust: 20–30%
• Bottom Ash: Up to 20%
• RCFA: 20–30%
• Crumb Rubber: Up to 15% (non-structural concrete)
• Foundry Sand: 20–25%
• Glass Powder: 20–30%

Conclusion

This experimental investigation confirms that the replacement of natural fine aggregate with sustainable recycled waste materials in concrete is both technically feasible and structurally viable across a range of replacement levels. M-Sand emerges as the most structurally suitable substitute, capable of maintaining or enhancing compressive, tensile, and flexural strength at replacement levels up to 100%, and representing the most direct and effective solution to river sand scarcity. Quarry Dust and Foundry Sand at 20–30% replacement levels yield concrete with mechanical properties closely comparable to conventional river sand concrete. Bottom Ash and RCFA are suitable for partial replacement at up to 20–30%, offering substantial environmental benefits in terms of industrial and construction waste diversion. Crumb Rubber, while significantly reducing concrete strength, imparts valuable ductility and energy absorption characteristics that make it appropriate for lightweight, non-structural, and impact-resistant applications. Glass Powder offers pozzolanic benefit and is promising in combination with other replacement materials. Collectively, the findings of this study support the conclusion that strategic, informed use of recycled waste materials as fine aggregate substitutes constitutes a technically credible, economically rational, and environmentally imperative dimension of sustainable concrete engineering, and merits integration into standard mix design practice and construction specifications.

References

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Copyright

Copyright © 2026 Aakanksha Panditrao Ingle, Prof. V. B. Chavan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.