Development and Characterization of Supplementary Cementitious Material from Phosphate and Sewage Sludge
Eurica MKHONTO, Thandiwe SITHOLE, Tebogo MASHIFANA
Abstract. The environmental impact associated with cement production highlights the need for alternative low-carbon binders that promote sustainability and circularity. There is limited research that investigates the combined use of sewage sludge (SS) and Phosphate sludge (P) as cement-free supplementary cementitious materials (SCM) that are normally discarded, while they contain pozzolanic elements. This study investigates the feasibility of developing composites with varied proportions of SS and P (40SS:60P, 50SS:50P, 60SS:40P) by evaluating their unconfined compressive strength (UCS) and environmental safety. The raw materials and the developed composite were characterized by their chemical composition using X-ray fluorescence (XRF), mineralogy via X-ray diffraction (XRD), microstructural analysis with a scanning electron microscope (SEM), and functional groups through Fourier-transform infrared spectroscopy (FTIR). The 60SS:40P ratio yielded the highest UCS of 0.89 MPa, with low to no metal leachability below the United States Environmental Protection Agency (USEPA). The analysis showed that the strength was influenced by the formation of C-A-F-S-H, C-S-H, and iron phosphate. The developed composite is suitable for application as backfilling and non-load-bearing blocks. The valorization of SS and P contributes to circularity and minimizes emissions from cement production while advancing SDG 12 (responsible consumption) and SDG 13 (climate action).
Keywords
Supplementary Cementitious Material, Sewage Sludge, Sustainable Material, Waste Beneficiation
Published online 4/2/2026, 8 pages
Copyright © 2026 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Eurica MKHONTO, Thandiwe SITHOLE, Tebogo MASHIFANA, Development and Characterization of Supplementary Cementitious Material from Phosphate and Sewage Sludge, Materials Research Proceedings, Vol. 63, pp 160-167, 2026
DOI: https://doi.org/10.21741/9781644904053-18
The article was published as article 18 of the book Advances in Cement and Concrete Research
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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