Understanding the strengthening of a lateritic “geomimetic” material

• Published in: Construction & building materials 2014-03, Vol.55, p.333-340
• Main Authors: Goure-Doubi, H., Lecomte-Nana, G., Nait-Abbou, F., Nait-Ali, B., Smith, A., Coudert, V., Konan, L.
• Format: Article
• Language: English
• Subjects: Analysis; Chemical properties; Chemical Sciences; Clay minerals; Compressive strength; Durability; Fulvic acid; Fulvic acids; Humic acid; Lateritic clay; Material chemistry; Rheology; “Geomimetic” material
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2014.01.064

“Geomimetic” materials consolidation involves an acidic and alkaline reaction steps and a curing period at 60°C for 18days under water saturated atmosphere. The use of lime (Ca(OH)2) or soda (NaOH) gives rise to consolidated products exhibiting similar compressive strengths. Soda-based products appear to be less resistant within water solution. The lime-based materials are good thermal insulators and their strengthening can be represented graphically as shown below. [Display omitted] •Lime-based and soda-based materials exhibit similar compressive strength.•Lime-based products present the lowest thermal conductivity and the highest durability.•Geopolymerisation-like interactions are promoted when using NaOH.•The yield stress and consistency are gradually increased during the aging period.•Binding phases occur after 4 days while a solid-like behaviour prevails after 7 days of aging at 60°C. The present work aimed to investigate the interactions that control the strengthening of “geomimetic” materials. The raw lateritic clay used mainly contained kaolinite, goethite, quartz and hematite. The processing involved a 24h-reaction with fulvic acid followed by neutralization with lime or with NaOH prior to the curing at 60°C for 18days under water saturated atmosphere. The compressive strength and thermal conductivity after consolidation were respectively 0.7MPa and 0.19Wm−1K−1 for lime-based products, and 0.78MPa and 0.3Wm−1K−1 for soda-based products. The latter exhibited low durability in water. Such differences could be related to the high degradation of kaolinite particles when using NaOH, leading to the formation of sodalite, cancrinite and nontronite, which phases did not act as binder. Cementitious CAH and CSH phases were obtained when using lime. Rheological measurements performed on lime-based samples indicated that a shear-thinning behavior prevails up to the 7th day of curing. Above this period, the samples reached a determinant step whereby a solid-like behavior became predominant. The occurrence of binding precursors during the first 7days of curing conducted to a progressive increase of the yield stress and consistency from 1 to 53Pa and from 0.2 to 2.3Pas, respectively.