Hybrid alkaline cements with low clinker content: Strength development, gel chemistry, and microstructural evolution
Reducing the use of Portland cement in binder formulations is a key strategy to mitigate the environmental impact of the construction industry. Hybrid alkaline cements, which combine Portland cement, supplementary cementitious materials, and alkaline activators, reduce clinker demand while maintaini...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:dnet:digitalcsic_::662092447577d18e7b2ddddc9507ed40 |
| Acceso en línea: | http://hdl.handle.net/10261/429063 https://api.elsevier.com/content/abstract/scopus_id/105033857374 |
| Access Level: | acceso embargado |
| Palabra clave: | Alkaline activation Fly ash Hybrid alkaline cements Low-clinker cements Metakaolin Microsilica Microstructural evolution |
| Sumario: | Reducing the use of Portland cement in binder formulations is a key strategy to mitigate the environmental impact of the construction industry. Hybrid alkaline cements, which combine Portland cement, supplementary cementitious materials, and alkaline activators, reduce clinker demand while maintaining comparable mechanical performance. Accordingly, in this study, low-clinker hybrid systems were formulated incorporating fly ash, metakaolin, and microsilica, and activated with either sodium sulfate (Na2SO4) or a combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Compressive strength was estimated at different curing ages, and the hydration process was investigated using isothermal calorimetry. The formation of crystalline and amorphous phases was evaluated using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The microstructure of the samples was analyzed by backscattered electron microscopy and energy-dispersive X-ray spectroscopy (BSEM–EDS). The highest compressive strengths were obtained in ternary fly ash–metakaolin–microsilica systems activated with NaOH + Na2SiO3, consistent with the precipitation of C–A–S–H and (N,C)–A–S–H gels. Sodium sulfate activation promoted rapid ettringite formation and higher early-age strength, although long-term performance was comparatively lower. The incorporation of microsilica refined the pore structure and densified the matrix, thereby improving the homogeneity of the cement matrix. Microstructural analyses confirmed denser reaction product formation in ternary blends than in binary systems. Within the scope of this study, the analysis focused on reaction kinetics, phase assemblage, and microstructural evolution; nevertheless, these results highlight the potential of hybrid alkaline cements with reduced clinker content to achieve high performance—up to 34 MPa at 28 days and 43 MPa at 365 days—while advancing understanding of gel chemistry and microstructural evolution. |
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