Comparison of surface properties between kaolin and metakaolin in concentrated lime solutions

• Published in: Journal of colloid and interface science Vol. 339; no. 1; pp. 103 - 109
• Main Authors: Konan, K.L., Peyratout, C., Smith, A., Bonnet, J.-P., Rossignol, S., Oyetola, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.11.2009; Elsevier
• Subjects: Calcium hydroxide; Chemistry; Clays; Colloidal state and disperse state; Differential thermal analysis; Engineering Sciences; Exact sciences and technology; General and physical chemistry; Hydrated phases; Kaolin; Lime; Materials; Metakaolin; Phases; Slaked lime; Surface chemistry; Surface physical chemistry; Metakaolin; Hydrated phases; Lime; Kaolin; Clay; Hydration; Differential thermal analysis; X ray diffraction; Dissolution; Calcium silicate; Particle; Hydrated ion; Calcium ion; Adsorption; Surface properties; pH; Calcium hydroxide; Hydroxyl; Interface; Concentrated solution
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2009.07.019

Surface adsorption of calcium and hydroxyl ions onto kaolin and metakaolin in concentrated lime solutions. The surface adsorption of calcium hydroxide onto kaolin and metakaolin was investigated by monitoring with atomic emission spectroscopy and pH measurements the amounts of ions left in solution after exposing clays to calcium hydroxide solutions of various concentrations. Both clays adsorb calcium and hydroxyl ions but differently. Kaolin adsorbs calcium hydroxide not only at the edges of the clay particles but also onto the basal faces. The adsorbed hydrated calcium ions form a layer on the clay particle surfaces, preventing further dissolution of the clay mineral platelet. Metakaolin shows high pozzolanic activity, which provides the quick formation of hydrated phases at the interfaces between metakaolin and lime solutions. The nature of the hydration products has been investigated using X-ray diffraction (XRD) and differential thermal analysis (DTA). The most important hydrated phases like CSH (hydrated calcium silicate) and C 2ASH 8 (gehlenite) have been identified.