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Abstract
This research explores the potentiality of biochar derived from faecal sludge collected at faecal sludge treatment plants (FSTP) by partially replacing cements used in concrete applications. These plants collect, treat, and manage human waste from septic tanks and sanitation systems. This study focuses on determining the optimal dose of biochar as application for concrete’s mechanical, durability properties, and microstructural changes. The biochar's pozzolanic activity was evaluated through the strength activity index, while parameters such as shrinkage, compressive strength, flexural strength, water absorption, and porosity were also measured to gauge its impact on concrete performance. Results indicate that incorporating biochar at specific dosages at 5% and 10% replacement yields significant improvements in concrete properties. After a 91-day curing period, concrete with a 10% biochar substitution demonstrated a 21% increase in compressive strength and a 42% increase in flexural strength, highlighting biochar’s contribution to mechanical performance. Water absorption and porosity values for concrete with a 15% biochar content were found to be comparable to those of conventional control mixes after 28 days of curing. After 120 days, the drying shrinkage observed in a 10% biochar mortar mix was like that in ordinary Portland cement (OPC) mortar, indicating the potential of biochar to maintain dimensional stability over extended periods. The reduction in heavy metal concentration in the concrete specimens due to the increased biochar content was also reported. This result successfully demonstrates, it is helpful to sustain environment by potentially lowering the leaching of harmful substances.
Abbreviations
- AAS:
-
Atomic absorption spectroscopy
- ASTM:
-
American society for testing and materials
- C-A-S-H:
-
Calcium–alumino–silicate–hydrate
- CH:
-
Calcium hydroxide or portlandite [Ca (OH)₂]
- C-S-H:
-
Calcium–silicate–hydrate
- DTG:
-
Differential thermogravimetry
- EDS/EDX:
-
Energy-Dispersive X-ray spectroscopy
- EN:
-
European standard
- FSTP:
-
Faecal sludge treatment plant
- FT-Ir :
-
Fourier transform infrared spectroscopy
- IS:
-
Indian standard
- ITZ:
-
Interfacial transition zone
- OPC:
-
Ordinary portland cement
- PSA:
-
Particle size analysis
- SEM:
-
Scanning electron microscopy
- SEM–EDS/EDX:
-
Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy
- SICART:
-
Sophisticated instrumentation centre for applied research and testing
- SAIF:
-
Sophisticated analytical instrument facility
- SMD:
-
Sauter mean diameter
- TGA:
-
Thermogravimetric analysis
- VMD:
-
Volume mean diameter
- w/b:
-
Water-to-binder ratio (by mass)
- w/c:
-
Water-to-cement ratio (by mass)
- XRD:
-
X-ray diffraction
- XRF:
-
X-ray fluorescence
- A:
-
Aluminum oxide (Al₂O₃)
- C:
-
Calcium oxide (CaO)
- CH:
-
Calcium hydroxide [Ca(OH)₂]
- F:
-
Ferric oxide (Fe₂O₃)
- H:
-
Water (H₂O)
- S:
-
Silicon dioxide (SiO₂)
Acknowledgement
The authors wish to thank Manipal University Jaipur for providing the support and infrastructure. The Authors also express their gratitude for the Manipal Research Board (MRB), Manipal Academy of Higher Education and Manipal University Jaipur for supporting the study. The authors thank Tide Technocrats Pvt. Ltd, Telangana, India for their extended support in providing biochar used in the present study. The authors would also like to extend appreciation to SICART, Gujrat and SAIF lab facility & the department of civil engineering at Manipal University Jaipur for all the help rendered in carrying out the research.
Funding
Open access funding provided by Manipal University Jaipur. This research did not receive specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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Competing interests
The authors declare no competing interests.
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The research has been scientifically consented to be published. Competing Interests The authors declare no competing interests.
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Cite this article
Tiwari, R., Mehra, P., Hussain, S. et al. Mechanical, durability, and microstructural performance of biochar-modified concrete using faecal sludge–derived biochar. Sci Rep (2026). https://doi.org/10.1038/s41598-026-66956-6
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DOI: https://doi.org/10.1038/s41598-026-66956-6