Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge
Abstract This study investigated the potential of wastewater sludge (WWS) as a partial replacement for fine aggregates in non-structural concrete to optimise its mechanical properties while mitigating environmental impacts. WWS from three wastewater treatment plants (WWTPs), Mankweng, Polokwane, and...
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Nature Portfolio
2025-05-01
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| Online Access: | https://doi.org/10.1038/s41598-025-04151-9 |
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| author | Kobe Samuel Mojapelo Williams Kehinde Kupolati Everardt Andre Burger Julius Musyoka Ndambuki Jacques Snyman Emmanuel Rotimi Sadiku Idowu David Ibrahim |
| author_facet | Kobe Samuel Mojapelo Williams Kehinde Kupolati Everardt Andre Burger Julius Musyoka Ndambuki Jacques Snyman Emmanuel Rotimi Sadiku Idowu David Ibrahim |
| author_sort | Kobe Samuel Mojapelo |
| collection | DOAJ |
| description | Abstract This study investigated the potential of wastewater sludge (WWS) as a partial replacement for fine aggregates in non-structural concrete to optimise its mechanical properties while mitigating environmental impacts. WWS from three wastewater treatment plants (WWTPs), Mankweng, Polokwane, and Seshego, in Limpopo Province, South Africa, was used to replace sand at 0, 5, 10, 15, and 20% by weight. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and energy-dispersive X-ray analysis (EDX) were used to characterise the organic compositions of the sludge and sludge-based concrete. The environmental safety of the sludge-based concrete was then assessed through the Toxicity Characteristic Leaching Procedure (TCLP) at 28, 90, and 140 days, ensuring compliance with heavy metal leaching limits. The results demonstrate that at a 5% replacement level, the concrete maintained an average compressive strength of 25 MPa after 90 days, meeting general construction standards for non-structural and low load-bearing applications. The incorporation of wastewater sludge had low leachable heavy metals, with TCLP results confirming all tested metals remained below regulatory limits throughout. However, increasing WWS content beyond 10% resulted in higher porosity, reduced compressive strength, and increased water absorption, which compromise durability. The findings highlight the importance of optimising replacement levels and mix design to balance sustainability, mechanical performance, and regulatory compliance. |
| format | Article |
| id | doaj-art-a05a19d5d8d6472f9733d8853d8d2d79 |
| institution | DOAJ |
| issn | 2045-2322 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | Nature Portfolio |
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| series | Scientific Reports |
| spelling | doaj-art-a05a19d5d8d6472f9733d8853d8d2d792025-08-20T03:22:12ZengNature PortfolioScientific Reports2045-23222025-05-0115111510.1038/s41598-025-04151-9Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludgeKobe Samuel Mojapelo0Williams Kehinde Kupolati1Everardt Andre Burger2Julius Musyoka Ndambuki3Jacques Snyman4Emmanuel Rotimi Sadiku5Idowu David Ibrahim6Department of Civil Engineering, Tshwane University of TechnologyDepartment of Civil Engineering, Tshwane University of TechnologyDepartment of Civil Engineering, Tshwane University of TechnologyDepartment of Civil Engineering, Tshwane University of TechnologyDepartment of Civil Engineering, Tshwane University of TechnologyInstitute for NanoEngineering Research (INER), Department of Chemical Metallurgy and Materials Engineering, Tshwane University of TechnologyDepartment of Industrial Engineering & Operations Management and Mechanical Engineering, Vaal University of TechnologyAbstract This study investigated the potential of wastewater sludge (WWS) as a partial replacement for fine aggregates in non-structural concrete to optimise its mechanical properties while mitigating environmental impacts. WWS from three wastewater treatment plants (WWTPs), Mankweng, Polokwane, and Seshego, in Limpopo Province, South Africa, was used to replace sand at 0, 5, 10, 15, and 20% by weight. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and energy-dispersive X-ray analysis (EDX) were used to characterise the organic compositions of the sludge and sludge-based concrete. The environmental safety of the sludge-based concrete was then assessed through the Toxicity Characteristic Leaching Procedure (TCLP) at 28, 90, and 140 days, ensuring compliance with heavy metal leaching limits. The results demonstrate that at a 5% replacement level, the concrete maintained an average compressive strength of 25 MPa after 90 days, meeting general construction standards for non-structural and low load-bearing applications. The incorporation of wastewater sludge had low leachable heavy metals, with TCLP results confirming all tested metals remained below regulatory limits throughout. However, increasing WWS content beyond 10% resulted in higher porosity, reduced compressive strength, and increased water absorption, which compromise durability. The findings highlight the importance of optimising replacement levels and mix design to balance sustainability, mechanical performance, and regulatory compliance.https://doi.org/10.1038/s41598-025-04151-9Wastewater sludgeHeavy metal leachingMechanical propertiesEnvironmental impactSustainable construction |
| spellingShingle | Kobe Samuel Mojapelo Williams Kehinde Kupolati Everardt Andre Burger Julius Musyoka Ndambuki Jacques Snyman Emmanuel Rotimi Sadiku Idowu David Ibrahim Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge Scientific Reports Wastewater sludge Heavy metal leaching Mechanical properties Environmental impact Sustainable construction |
| title | Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge |
| title_full | Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge |
| title_fullStr | Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge |
| title_full_unstemmed | Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge |
| title_short | Optimising the mechanical properties of concrete for non-structural applications through partial replacement of fine aggregates with wastewater sludge |
| title_sort | optimising the mechanical properties of concrete for non structural applications through partial replacement of fine aggregates with wastewater sludge |
| topic | Wastewater sludge Heavy metal leaching Mechanical properties Environmental impact Sustainable construction |
| url | https://doi.org/10.1038/s41598-025-04151-9 |
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