| Title |
Elaboration of geopolymers based on clays by-products from phosphate mines for construction applications |
| ID_Doc |
25228 |
| Authors |
Mabroum, S; Aboulayt, A; Taha, Y; Benzaazoua, M; Semlal, N; Hakkou, R |
| Title |
Elaboration of geopolymers based on clays by-products from phosphate mines for construction applications |
| Year |
2020 |
| Published |
|
| DOI |
10.1016/j.jclepro.2020.121317 |
| Abstract |
Yellow clays from Moroccan phosphate mines are extracted with other waste rocks lithologies and stored in large dumps within the mine site. The present paper investigates the use of this by-product as a new aluminosilicate source for geopolymers elaboration at the laboratory scale. Yellow clays studied are mainly composed of montmorillonite, dolomite and quartz as major phases. The Toxicity Characteristic Leaching Procedure (TCLP) showed no existence of contaminant. In order to reach thermal activation, the raw clays were first calcined at different temperatures between 500 and 900 degrees C. Raw and calcined clays were characterized using thermogravimetric analysis (TGA), X-Ray Diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy. For the synthesis of geopolymers, calcined powder was mixed with an alkaline solution presenting different NaOH/Na2SiO3 ratios. The compressive strength was measured at 7, 14 and 28 days and material porosity was determined using Mercury Intrusion Porosimetry method in order to explain the mechanical behavior. XRD, 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy, Fourier transformed infrared and TGA have been used to investigate the gel structure. The thermal treatment at 900 degrees C allowed the destruction of crystalline structure of montmorillonite clays, as well as the formation of new phases such as periclase (MgO) and gehlenite (Ca2Al2SiO7). Furthermore, the Al-27 - Si-29 MAS-NMR and the XRD analysis of the elaborated materials confirmed the formation of two cementitious gels C-A-S-H (Calcium aluminum silicate hydrate) and N-A-S-H (Sodium aluminum silicate hydrate). The compressive strength was around 25 MPa at 28 days. The obtained results are promising; they have shown that elaborated materials can be adapted for construction applications. In this case, it is recommended that economic and commercial study be developed. (C) 2020 Elsevier Ltd. All rights reserved. |
| Author Keywords |
Phosphate mines; Mine waste; Clayey lithology; Valorization; Geopolymers; Circular economy |
| Index Keywords |
Index Keywords |
| Document Type |
Other |
| Open Access |
Open Access |
| Source |
Science Citation Index Expanded (SCI-EXPANDED) |
| EID |
WOS:000533537200010 |
| WoS Category |
Green & Sustainable Science & Technology; Engineering, Environmental; Environmental Sciences |
| Research Area |
Science & Technology - Other Topics; Engineering; Environmental Sciences & Ecology |
| PDF |
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