Alkaline and Acid Activations of Calcined Laterites: A Comparative Study

• Published in: SILICON Vol. 15; no. 6; pp. 2797 - 2810
• Main Authors: Tantono, Solomon Ndisho, Belibi Belibi, Placide Desire, Baenla, Jean, Elimbi, Antoine
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-04-2023; Springer Nature B.V
• Subjects: Acids; Building materials; Bulk density; Chemistry; Chemistry and Materials Science; Comparative studies; Compressive strength; Construction materials; Environmental Chemistry; Fourier transforms; Inorganic Chemistry; Lasers; Laterites; Materials Science; Metakaolin; Optical Devices; Optics; Original Paper; Phosphoric acid; Phosphorus pentoxide; Photonics; Polymer Sciences; Roasting; Silicon dioxide; Sodium hydroxide; Water absorption; Calcined laterite, Alkaline activation, Acid activation, Inorganic polymers, Comparative study
• ISSN: 1876-990X; 1876-9918
• DOI: 10.1007/s12633-022-02211-7

In order to improve the characteristics of natural laterites for earth building issues, activation of three calcined laterites was carried out in both alkaline solutions of constant SiO
2
/ Na
2
O molar ratio of 1.4 and in phosphoric acid of various P
2
O
5
/ H
2
O molar ratios (0.06 to 0.15 respectively). Depending on the natural or the calcined laterites along with their activated products, X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), compressive strength, water absorption, bulk density and Strength Retention Coefficient (SRC) were performed. Optimal compressive strengths were achieved respectively in alkaline solution whose sodium hydroxide was 12 M and in phosphoric acid with P
2
O
5
/ H
2
O molar ratio of 0.09. Compressive strength of the products ranged between 2.0 and 18.8 MPa (alkaline media) and between 18.9 and 52.4 MPa (phosphoric acid media). Under wet condition, there was decrease of compressive strength of up to 31.9% in alkaline medium as compared to up to 20.6% in acidic one. To get better earth building materials, activation of calcined laterites is more effective in phosphoric acid than in alkaline medium. In fact, contrarily to alkaline medium that is mostly concerned with metakaolin, phosphoric acid allows an additional activation with certain oxides contained in calcined laterites.