Sustainable Application of Copper Slag as Fine Aggregate in High-Strength Concrete

Abstract

The growing consumption of natural river sand in concrete manufacturing has led to serious environmental degradation and material scarcity, emphasizing the need for sustainable substitute materials. Copper slag, a by-product generated during the copper smelting process, has emerged as a potential alternative to fine aggregate in high-strength concrete. This investigation examines the behavior of M60 grade concrete in which copper slag replaces natural sand at proportions of 0%, 20%, 40%, 60%, 80%, and 100%. The fresh concrete properties were assessed using slump cone tests, whereas the hardened properties were evaluated through compressive strength tests conducted at 7, 14, and 28 days, along with split tensile and flexural strength tests performed at 28 days. The experimental results revealed an increase in workability with rising copper slag content, attributed to its smooth surface characteristics and minimal water absorption capacity. The highest compressive strength was recorded at a 40% replacement level, showing noticeable improvement over the conventional mix. However, replacement levels exceeding 60% resulted in a reduction in strength due to increased free water content and weaker interfacial bonding between the paste and aggregates. Similar performance patterns were observed for split tensile and flexural strengths, with optimal results obtained within the 40–60% replacement range. The study concludes that copper slag can effectively substitute up to 60% of natural sand in M60 grade concrete without adversely affecting structural performance, thereby supporting sustainable construction and efficient utilization of industrial waste.

Introduction

Concrete is widely used in construction, but its production depends heavily on natural river sand, whose excessive extraction has caused environmental damage such as riverbank erosion, groundwater depletion, and ecological imbalance. Due to rising costs and limited availability of natural sand, alternative materials are being explored. Copper slag, a by-product of copper smelting, has emerged as a promising replacement for fine aggregate in concrete. Its favorable properties—high density, angular shape, low water absorption, and chemical stability—make it suitable for sustainable construction while reducing industrial waste disposal issues.

This study evaluates the use of copper slag as a partial and full replacement of fine aggregate in M60 grade high-strength concrete. Replacement levels of 0%, 20%, 40%, 60%, 80%, and 100% were tested. Fresh and hardened properties were examined, including workability (slump test), compressive strength, split tensile strength, and flexural strength.

Results showed that workability increased consistently with higher copper slag content due to its smooth texture and low water absorption. However, excessive replacement (above 60%) risked segregation and bleeding. Mechanical properties improved significantly up to 40% replacement, where maximum 28-day strengths were achieved:

• Compressive strength: 78 MPa

• Split tensile strength: 5.4 MPa

• Flexural strength: 9.3 MPa

Beyond 60% replacement, strength gradually decreased due to weaker bonding and increased free water content in the concrete matrix.

The study concludes that 40–60% copper slag replacement provides optimal performance in high-strength concrete, enhancing mechanical properties while promoting sustainability and responsible industrial waste utilization.

Conclusion

1) The workability of concrete increased steadily with higher copper slag content as a result of its smooth surface characteristics and low water absorption capacity. However, excessive workability observed at replacement levels of 80–100% may cause segregation and bleeding. 2) Maximum compressive strength was attained at a 40% replacement level, achieving 78 MPa at 28 days, which corresponds to an improvement of nearly 15% over the conventional control mix. A reduction in strength was noted beyond 60% replacement. 3) Split tensile strength followed a trend similar to compressive strength, reaching a peak value of 5.4 MPa at 40% replacement. This indicates improved resistance to tensile cracking at moderate levels of copper slag incorporation. 4) Flexural strength also benefited from the inclusion of copper slag, with the highest value of 9.3 MPa recorded at 40% replacement. This demonstrates enhanced bending resistance in high-strength concrete containing copper slag at optimal levels. 5) All strength parameters exhibited a decline when copper slag replacement exceeded 60%, mainly due to weaker interfacial transition zone bonding and increased free water content. 6) Based on the experimental findings, a replacement range of 40–60% of natural fine aggregate with copper slag is recommended as the optimum for M60 grade high-strength concrete. 7) The incorporation of copper slag contributes to improved mechanical performance while simultaneously promoting sustainable construction practices by reducing dependence on natural sand and facilitating the effective utilization of industrial waste. 8) From an economic perspective, copper slag serves as a cost-efficient alternative to natural sand, particularly in areas where it is readily available.

References

[1] Ambily, P.S., Kumar, S., Kaliyavaradhan, K., Sebastian, S., & Shekar, D. 2025, ‘Sustainable 3D Printable Concrete Mix Using Copper Slag’, Journal of Building Engineering, vol. 101, p. 111950. [2] Ahirwar, S.K., & Mandal, J.N. 2021, ‘Experimental study on bamboo grid reinforced copper slag overlying soft subgrade’, Construction and Building Materials, vol. 306, p. 124758. [3] Afshoon, I., & Sharifi, Y. 2023, ‘Evaluating the flexural behavior of green copper slag-contained steel fiber reinforced SCC beams with/without initial notches’, Construction and Building Materials, vol. 395, p. 131708. [4] Afshoon, I., Miri, M., & Mousavi, S.R. 2023, ‘Prediction model and measurement of fracture parameters in eco-friendly coarse copper slag-SFRSCC based on semi-circular bending test’, Construction and Building Materials, vol. 367, p. 133418. [5] Afshoon, I., Miri, M., & Mousavi, S.R. 2023, ‘Comprehensive experimental and numerical modeling of strength parameters of eco-friendly steel fiber reinforced SCC containing coarse copper slag aggregates’, Construction and Building Materials, vol. 367, p. 130304. [6] Afshoon, I., Miri, M., & Mousavi, S.R. 2024, ‘Investigation of mode I fracture behavior of copper slag-SFRSCC’, Engineering Structures, vol. 315, p. 118513. [7] Bureau of Indian Standards (BIS), IS 383:2016 – Specification for Coarse and Fine Aggregates for Concrete, Bureau of Indian Standards, New Delhi, India. [8] Bureau of Indian Standards (BIS), IS 2386 (Part 1-8): 1963 – Methods of Test for Aggregates for Concrete, Bureau of Indian Standards, New Delhi, India. [9] Bureau of Indian Standards (BIS), IS 6240:2008 – Specification for Copper Slag, Bureau of Indian Standards, New Delhi, India. [10] Bureau of Indian Standards (BIS), IS 10262:2019 – Guidelines for Concrete Mix Design Proportioning, Bureau of Indian Standards, New Delhi, India. [11] Bureau of Indian Standards (BIS), IS 456:2000 – Code of Practice for Plain and Reinforced Concrete, Bureau of Indian Standards, New Delhi, India. [12] Bureau of Indian Standards (BIS), IS 516 (Part 1): 2020 – Method of Tests for Strength of Concrete, Bureau of Indian Standards, New Delhi, India. [13] Bureau of Indian Standards (BIS), IS 1199:1959 – Methods for Sampling and Analysis of Fresh Concrete, Bureau of Indian Standards, New Delhi, India. [14] Bureau of Indian Standards (BIS), IS 4031 (Part 1-15): 1988 – Methods of Physical Tests for Hydraulic Cement, Bureau of Indian Standards, New Delhi, India. [15] Bureau of Indian Standards (BIS), IS 5816:1999 – Splitting Tensile Strength of Concrete, Bureau of Indian Standards, New Delhi, India. [16] Bureau of Indian Standards (BIS), IS 516 (Part 2): 2020 – Durability Testing Methods for Concrete, Bureau of Indian Standards, New Delhi, India. [17] Bureau of Indian Standards (BIS), IS 15388:2003 – Guidelines for Utilization and Disposal of Industrial Waste Materials in Cement and Concrete, Bureau of Indian Standards, New Delhi, India. [18] Clement, D., Rajasekaran, C., & Tiwari, M. 2025, ‘Assessment on the effectiveness of chemical admixture in processed laterite and copper slag based geopolymer mortar’, Construction and Building Materials, vol. 464, p. 130123. [19] Casagrande, C.A., Roque, J.S., Jochem, L.F., Correa, J.N., & Medeiros, A. 2023, ‘Copper slag in cementitious composites: A systematic review’, Journal of Building Engineering, vol. 78, p. 107725. [20] Deep, A., & Zade, N.P. 2024, ‘Exploring the viability of copper slag geopolymer concrete in structural applications: A study on strength variability and seismic risk assessment’, Structures, vol. 70, p. 107670. [21] Divya, S., & Praveenkumar, S. 2024, ‘An integrated evaluation of graphene-based concrete mixture with copper slag and quarry dust using response surface methodology’, Journal of Building Engineering, vol. 2024, p. 108876. [22] Edwin, R.S., Gruyaert, E., & De Belie, N. 2022, ‘Valorization of secondary copper slag as aggregate and cement replacement in ultra-high performance concrete’, Journal of Building Engineering, vol. 52, p. 104567. [23] Gong, W., Chen, Q., & Miao, J. 2021, ‘Bond behaviors between copper slag concrete and corroded steel bar after exposure to high temperature’, Journal of Building Engineering, vol. 44, p. 103312. [24] Gómez-Casero, M.A., Bueno-Rodríguez, S., Castro, E., & Quesada, D.E. 2024, ‘Alkaline activated cements obtained from ferrous and non-ferrous slags: Electric arc furnace slag, ladle furnace slag, copper slag and silico-manganese slag’, Cement and Concrete Composites, vol. 2024, p. 105427. [25] Hima, B.K., 2023, ‘Experimental studies on mechanical properties of copper slag reinforced concrete beams under static loading’, AIP Conference Proceedings, vol. 3101, p. 070002 [26] Haque, M.M., Ankur, N., Meena, A., & Singh, N. 2024, ‘Carbonation and permeation behaviour of geopolymer concrete containing copper slag and coal ashes’, Developments in the Built Environment, vol. 16, p. 100123. [27] Katlav, M., Donmez, I., & Turk, K. 2024, ‘Electrical resistivity of eco-friendly hybrid fiber-reinforced SCC: Effect of ground granulated blast furnace slag and copper slag content as well as hooked-end fiber length’, Construction and Building Materials, vol. 2024, p. 137235. [28] Luo, Y., Zhou, X., Luo, Z., Ma, H., Wei, Y., & Liu, Q. 2022, ‘A novel iron phosphate cement derived from copper smelting slag and its early age hydration mechanism’, Cement and Concrete Composites, vol. 133, p. 104653. [29] Li, M., Wang, L., Chang, S., & Liu, S. 2024, ‘Comparative study on preparation and hydration mechanism of composite cementitious materials containing copper slag’, Construction and Building Materials, vol. 350, p. 128902. [30] Liu, B., Zhang, Q., Feng, Y., Chen, Q., & Guo, L. 2024, ‘Mechanical and microstructural analysis of cemented tailings backfill by copper slag through alkaline activation emphasizing red mud’, Construction and Building Materials, vol. 350, p.128902.

Copyright

Copyright © 2026 Swapnali Mane, G. H. Dake. 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.