Development of sustainable materials from phosphate-activated by-products: Thermal and structural properties
This paper presents an innovative approach to the development of phosphate-based binders through a geopolymerization-inspired process using alternative activators and precursors. A clay by-product (phosphate waste rock), containing montmorillonite and dolomite, was selected as the precursor. Phospha...
| Autores: | , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/402883 |
| Acceso en línea: | http://hdl.handle.net/10261/402883 https://api.elsevier.com/content/abstract/scopus_id/105013659369 |
| Access Level: | acceso embargado |
| Palabra clave: | Acidic activator Alternative binders Clay by-product Phosphate salts Hydroxyapatite Phosphate mine wastes |
| Sumario: | This paper presents an innovative approach to the development of phosphate-based binders through a geopolymerization-inspired process using alternative activators and precursors. A clay by-product (phosphate waste rock), containing montmorillonite and dolomite, was selected as the precursor. Phosphate salts, including NaH2PO4, KH2PO4, and (NaPO3)n, were used as activators. Different analyses were performed to evaluate the potential of both precursors and activators, develop the alternative binders, and investigate the types of reaction products formed. The mechanical properties and microstructure of pastes prepared with previous materials were explored. The reaction products were characterized from the mineralogical (XRD, FTIR), microstructural (TEM/EDS), and nanostructural (29Si, 27Al, and 31P NMR) perspectives. Results showed that, regardless of the type and proportion of activator used, hydroxyapatite was the predominant crystalline phase precipitated in all the cementitious systems, with portlandite, brucite, and hydrotalcite detected as secondary phases. In addition, TEM and NMR analyses performed on alternative binders containing 10 % of each activator confirmed the formation of a common amorphous content, identified as C-(A)-S-H gel. However, increasing the NaH2PO4 content resulted in changes in the reaction products. The amount of hydroxyapatite increased, hydrotalcite disappeared, and new gel phases were detected, labeled as (N,C)-A-S-H and N-A-S-H gels (both containing Mg). This study highlights the potential of phosphate salts as innovative activators in the development of a new type of binder, offering a novel alternative within the field. Furthermore, the thermal conductivity results of materials developed with 10 % phosphate salts confirm their suitability for thermal insulation applications, where high compressive strength is not critical. |
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