Microstructural and mechanical properties of (Ca, Na)-poly(sialate-siloxo) from metakaolin as aluminosilicate and calcium silicate from precipitated silica and calcined chicken eggshell
| Autor: | Flore Mpombo Tchuente, Hervé K. Tchakouté, Cristina Leonelli, Fernanda Andreola, Elie Kamseu, Claus H. Rüscher, Charles Banenzoué |
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| Rok vydání: | 2019 |
| Předmět: |
Precipitated silica
Aluminate 0211 other engineering and technologies chemistry.chemical_element 020101 civil engineering 02 engineering and technology Building and Construction Calcium Silicate 0201 civil engineering Geopolymer chemistry.chemical_compound (Ca Na)-poly(sialate-siloxo) Apparent density Calcium silicate Compressive strengths Hardener Metakaolin chemistry Chemical engineering 021105 building & construction General Materials Science Calcium silicate hydrate Civil and Structural Engineering |
| Zdroj: | Construction and Building Materials. 201:662-675 |
| ISSN: | 0950-0618 |
| DOI: | 10.1016/j.conbuildmat.2018.12.219 |
| Popis: | The aim of this work is to investigate the influence of the amorphous calcium silicate on the microstructural, physical and mechanical properties of (Ca, Na)-poly(sialate-siloxo) networks. The calcium silicate with molar ratio CaO/SiO2 equal to 1.0 was prepared from the precipitated silica and calcined chicken eggshell. The X-ray patterns and infrared spectra of the synthesized calcium silicate indicate that it mainly constitutes of the amorphous calcium silicate hydrate. The X-ray patterns of geopolymer cements indicate that the prepared amorphous calcium silicate hydrate does not include in the network. The compressive strengths of the geopolymer mortars decrease from 28.92 to 12.03 MPa with increasing the replacement level of metakaolin (from 0 to 25% by mass). Whereas, the values of the apparent densities increase with increasing the replacement level of metakaolin. It seems that the amorphous calcium silicate hydrate in the structure of calcium silicate affects negatively the mechanical properties of the (Ca, Na)-poly(sialate-siloxo) network. The heterogeneous structure of geopolymer mortars containing 25% of calcium silicate could be related to the higher calcium content and the amorphous structure of calcium silicate hydrate. It was typically found that in the absence of significant levels of dissolved calcium, the precursors such as silicate and aluminate condense to form (Ca, Na)-poly(sialate-siloxo) networks. This implies the homogenous structure and the higher values of the compressive strengths of geopolymer mortars containing 0, 5, 10 and 15% of calcium silicate. Whereas those from the replacement level of metakaolin by 20 or 25% of calcium silicate contain significant levels of dissolved calcium and amorphous calcium silicate hydrate in their structure which hinder the formation of the precursors and therefore impede the formation of the (Ca, Na)-poly(sialate-siloxo) networks. |
| Databáze: | OpenAIRE |
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