The Influence of the Water–Cement Ratio on the Mechanical Properties of Cement Mortars with the Addition of Sewage Sludge Biochar
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Abstract
The article describes the research on the impact of sewage sludge biochar (SSB) on the mechanical and microstructural properties of cement mortars, with a focus on compressive and flexural strength. Ordinary Portland cement was partially replaced with biochar in amounts of 2%, 5%, and 10% by weight, at two different water-to-cement (w/c) ratios: 0.5 and 0.6. The research included a wide range of analyses, such as workability tests, strength tests after 7 and 28 days, microstructural examinations (using SEM, EDX, XRD) and fire resistance tests. The analysis showed that increasing biochar content reduced workability, especially at lower w/c ratios. At w/c = 0.5, the addition of biochar generally led to reduced compressive and flexural strength, particularly after 28 days. However, at w/c = 0.6, biochar significantly improved strength properties, with 2–5% being the most beneficial content. The study attributes the strength improvement to the filler effect, internal curing potential, and enhanced hydration due to biochar’s porous structure, which initially absorbs and later releases water. Microstructural analysis confirmed that biochar was well integrated into the cement matrix and facilitated the formation of calcium-silicate-hydrate (C–S–H) gels. Fire resistance tests further revealed that biochar-containing samples maintained higher compressive strength after exposure to high temperatures compared to the control samples. Overall, the study concludes that sewage sludge biochar has promising potential as a partial cement substitute, particularly at optimal doses (≤ 5%) and higher w/c ratios, contributing to sustainability goals in the construction sector.
Source: openalex_inverted_index · Quality: baseline
Research context
OpenAlex topics: Concrete and Cement Materials Research · Fire effects on concrete materials · Flame retardant materials and properties
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References (23)
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1. British Standards Institution. (2011). BS EN 197–1:2011 Cement - Part 1: Composition specifications and conformity criteria for common cements. Milton Keynes: BSI.
2. British Standards Institution. (2019). BS EN 1015–11:2019 Methods of test for mortar for masonry - Part 11: Determination of flexural and compressive strength of hardened mortar. Milton Keynes: BSI.
3. Barissov, T. (2021). Application of biochar as beneficial additive in concrete. Univ. of Nebraska. Retrieved from March 27, 2023, https://digitalcommons.unl.edu/civilengdiss/175.
4. Chen, L., et al. (2023). A review on the roles of biochar incorporated into cementitious materials: Mechanisms, application and perspectives. Construction and Building Materials. https://doi.org/10.1016/j.conbuildmat.2023.13420410.1016/j.conbuildmat.2023.134204 ↗
5. Cheng, D., Reiner, D. M., Yang, F., et al. (2023). Projecting future carbon emissions from cement production in developing countries. Nature Communications, 14, Article 8213. https://doi.org/10.1038/s41467-023-43660-x10.1038/s41467-023-43660-x ↗
6. Diatta, A. A., Fike, J. H., Battaglia, M. L., Galbraith, J. M., & Baig, M. B. (2020). Effects of biochar on soil fertility and crop productivity in arid regions: A review. Arabian Journal of Geosciences, 13(595), 1–17. https://doi.org/10.1007/s12517-020-05586-210.1007/s12517-020-05586-2 ↗
7. Gupta, S., Kua, H. W., & Koh, H. J. (2018a). Application of biochar from food and wood waste as green admixture for cement mortar. Science of the Total Environment, 619, 419–435. https://doi.org/10.1016/j.scitotenv.2017.11.02710.1016/j.scitotenv.2017.11.027 ↗
8. Gupta, S., Kua, H. W., & Low, C. Y. (2018b). Use of biochar as carbon sequestering additive in cement mortar. Cement and Concrete Composites, 87, 110–129. https://doi.org/10.1016/j.cemconcomp.2017.12.00910.1016/j.cemconcomp.2017.12.009 ↗
9. Horton, H., Mason, R., & Walker, P. (2023). Starmer accuses government of ‘turning Britain’s waterways into an open sewer. The Guardian. Retrieved from April 4, 2023, https://www.theguardian.com/environment/2023/mar/31/raw-sewage-spilledenglish-rivers-824-times-day-last-year
10. Kacprzak, M., Neczaj, E., Fijałkowski, K., Grobelak, A., Grosser, A., Worwag, M., Rorat, A., Brattebø, H., Almås, A., & Singh, B. R. (2017). Sewage sludge disposal strategies for sustainable development. Environmental Research, 156, 39–46. https://doi.org/10.1016/j.envres.2017.03.01010.1016/j.envres.2017.03.010 ↗
11. Legan, M., Žgajnar Gotvajn, A., & Zupan, K. (2022). Potential of biochar use in building materials. Journal of Environmental Management, 309, Article 114704. https://doi.org/10.1016/j.jenvman.2022.11470410.1016/j.jenvman.2022.114704 ↗
12. Major, J., Steiner, C., Downie, A., & Lehmann, J. (2012). Biochar effects on nutrient leaching. Biochar for Environmental Management (pp. 303–320). Oxfordshire: Routledge.
13. Mensah, R. A., Shanmugam, V., Narayanan, S., Razavi, S. M. J., Ulfberg, A., Blanksvärd, T., Sayahi, F., Simonsson, P., Reinke, B., Försth, M., Sas, G., Sas, D., & Das, O. (2021). Biochar-added cementitious materials—a review on mechanical, thermal, and environmental properties. Sustainability, 13(16), 1–22. https://doi.org/10.3390/su1316873410.3390/su13168734 ↗
14. Mrad, R., & Chehab, G. (2019). Mechanical and microstructure properties of biochar-based mortar: An internal curing agent for PCC. Sustainability, 11(9), Article 2491. https://doi.org/10.3390/su1109249110.3390/su11092491 ↗
15. Onuaguluchi, O., et al. (2024). Sludge-derived biochar as an additive in cement mortar: Mechanical strength and life cycle assessment (LCA). Construction and Building Materials, 425, Article 135959. https://doi.org/10.1016/j.conbuildmat.2024.13595910.1016/j.conbuildmat.2024.135959 ↗
16. Praneeth, S., Guo, R., Wang, T., Dubey, B. K., & Sarmah, A. K. (2020). Accelerated carbonation of biochar reinforced cement-fly ash composites: Enhancing and sequestering CO2 in building materials. Construction and Building Materials, 244, Article 118363. https://doi.org/10.1016/j.conbuildmat.2020.11836310.1016/j.conbuildmat.2020.118363 ↗
17. Qin, Y., Pang, X., Tan, K., & Bao, T. (2021). Evaluation of pervious concrete performance with pulverized biochar as cement replacement. Cement and Concrete Composites, 119, Article 104022. https://doi.org/10.1016/j.cemconcomp.2021.10402210.1016/j.cemconcomp.2021.104022 ↗
18. Scrivener, K. L., Füllmann, T., Gallucci, E., Walenta, G., & Bermejo, E. (2004). Quantitative study of Portland cement hydration by x-ray diffraction/Rietveld analysis and independent methods. Cement and Concrete Research, 34(9), 1541–1547. https://doi.org/10.1016/j.cemconres.2004.04.01410.1016/j.cemconres.2004.04.014 ↗
19. Sikora, P., et al. (2022). A systematic experimental study on biochar-cementitious composites: Towards carbon sequestration. Industrial Crops and Products, 184, Article 115103. https://doi.org/10.1016/j.indcrop.2022.11510310.1016/j.indcrop.2022.115103 ↗
20. The Office of National Statistics. (2020). Atmospheric emissions: Greenhouse gases by industry and gas. Retrieved from November 20, 2022, https://www.ons.gov.uk/economy/environmentalaccounts/datasets
21. UK Biochar Research Centre. (2013). Pyrolysis research at UKBRC. Edinburgh, UK, Retrieved from December 17, 2022.
22. van Zwieten, L., Kimber, S., Morris, S., Chan, K. Y., Downie, A., Rust, J., Joseph, S., & Cowie, A. (2010). Effects of biochar from slow pyrolysis of papermill waste on agronomic performance and soil fertility. Plant and Soil, 327(1), 235–246. https://doi.org/10.1007/s11104-009-0050-x10.1007/s11104-009-0050-x ↗
23. Yang, X., Lin, R.-S., Han, Y., & Wang, X.-Y. (2021). Behavior of biochar-modified cementitious composites exposed to high temperatures. Materials, 14(18), Article 5414. https://doi.org/10.3390/ma1418541410.3390/ma14185414 ↗