Effect of iron phase on the strengthening of lateritic-based “geomimetic” materials

• Published in: Applied clay science 2012-12, Vol.70, p.14-21
• Main Authors: Lecomte-Nana, Gisèle, Goure-Doubi, Hervé, Smith, Agnès, Wattiaux, Alain, Lecomte, Gilles
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Ferric gels; Fulvic acid; Iron oxides and oxyhydroxides; Lateritic clay; Material chemistry; Mineralogy; Phase transformation; Silicates; “Geomimetic” materials
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2012.09.014

The present work aims to investigate the action of associated iron species contained in lateritic clays in the strengthening process of “geomimetic” materials (compressive strength of 12MPa). The starting products are a lateritic clay from Cameroon, fulvic acid and lime. The synthesis involves acidic and alkaline reactions followed by a curing period of 18days at 60°C under water-saturated atmosphere. Since goethite (α-FeOOH), hematite (α-Fe2O3) and ferrihydrite (5Fe2O3·9H2O) are the main iron compounds in the raw clay, investigations have been carried out to identify to which extend each of these phases participates in the consolidation process. It appears that hematite and ferrihydrite may contribute to the consolidating mechanism since the as obtained “geomimetic” products exhibit characteristic compressive strength of 8.3 and 4.5MPa respectively. Besides, the use of goethite leads to consolidated products with characteristic compressive strength of 6.5MPa. The strengthening is effective when the synthesis of iron species is performed separately (no direct precipitation onto kaolin particles). Moreover, among the various model samples tested, only those elaborated with goethite were resistant towards water seeping and wearing. Hence, goethite is considered as the major active phase in the dissolution precipitation reaction which leads to bridging ferric gels. The elaboration of «geomimetic» materials involves acidic and alkaline reaction steps which contribute to the further consolidation of the material after curing at 60°C for 18days under water saturated atmosphere. Associated iron species, mainly goethite seems to play a major role in this strengthening process as summarized below. [Display omitted] ► Low temperature consolidation of environmental friendly material has been achieved. ► Direct precipitation of iron phases onto kaolin does not promote the strengthening. ► Hematite and ferrihydrite lead to consolidated but not water resistant products. ► Goethite is the major active iron phase for the processing of “geomimetic” materials.