Low-Carbon binder development using silica fume, GGBS and coal-washery rejects and elevation of mechanical performance with environmental significance
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Full Text |
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Author |
Shashidhar Reddy G. and Ramesh B.
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e-ISSN |
1819-6608 |
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On Pages
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414-429
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Volume No. |
21
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Issue No. |
7
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Issue Date |
June 10, 2026
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DOI |
https://doi.org/10.59018/042650
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Keywords |
silica fume, GGBS, CWR, SEM-EDS analysis, low-carbon binders, hydration chemistry, and sustainable cementitious materials.
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Abstract
This study examines the chemical characteristics, microstructural behaviour and strength evolution of a low-carbon blended binder incorporating silica fume (15%), ground granulated blast-furnace slag (20%), coal-washery rejects (15%) and ordinary Portland cement (50%). Coal-washery rejects were processed to a particle size below 75 μm and utilized as a supplementary component within the binder system. Elemental characterization using SEM-EDS confirmed the presence of oxygen (44.6%), silicon (13.3%), calcium (10.4%), carbon (8.9%), iron (6.0%), aluminum (5.1%), potassium (3.4%), phosphorus (3.3%), magnesium (1.7%), titanium (0.6%) and sodium (0.6%), indicating a mineralogical composition compatible with cementitious reactions. Microstructural assessment revealed the development of a dense hydration matrix dominated by calcium-silicate-hydrate (C-S-H) gel and uniformly distributed reaction products. SEM-EDS mapping demonstrated effective interaction among silica fume, GGBS, and coal-washery rejects, with silica fume enhancing secondary C-S-H formation and GGBS contributing to sustained hydration and matrix densification. Progressive refinement of gel phases and Si-Ca co-located regions was observed with curing, supporting continuous strength development. Compressive strength increased steadily from 24.8 MPa at 3 days to 34.2 MPa at 7 days, 48.9 MPa at 28 days, and 58.3 MPa at 90 days, reflecting effective hydration and microstructural evolution. Thermal and phase analyses further confirmed partial consumption of portlandite and increased amorphous gel formation, consistent with strong pozzolanic and latent hydraulic activity. From an environmental perspective, replacing 50% of ordinary Portland cement with industrial byproducts substantially reduces clinker demand and associated CO2 emissions while enabling beneficial utilization of coal-washery waste. The results demonstrate that coal-washery rejects can be effectively integrated into silica fume and GGBS-based blended binders, providing a technically robust and environmentally sustainable pathway for low-carbon cementitious material development.
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