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Alkali-Activated Materials Based on Callovo-Oxfordian Argillite: Formation, Structure and Mechanical Properties

C. Dupuy, C. Dupuy, A. Gharzouni, N. Texier-Mandoki, X. Bourbon, S. Rossignol

Journal of Ceramic Science and Technology, Vol. 9, No. 2 (2018), pp. 127-140

DOI: 10.4416/JCST2017-00086

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Abstract

If accepted, the construction of Cigéo, a French geological disposal facility for radioactive waste, will lead to the excavation of a large quantity of Callovo-Oxfordian (COx) argillite. The valorization of this raw material by alkaline activation was studied. For this, COx argillite without and with thermal treatment at 750 °C using furnace and flash processes were investigated. These treatments led mainly to the dehydroxylation of clay minerals and the decomposition of carbonate compounds. The feasibility of the alkali-activated samples based on different argillite samples and their mixtures was evaluated. Then, the consolidated samples were characterized by FTIR, X-ray diffraction, thermal analysis and compressive strength measurements. The results demonstrate that alkali activation is possible for all samples that contain at least 25 % calcined argillite (using both furnace and flash treatments). However, only samples without raw argillite indicate the formation of a geopolymer network and exhibit sufficient compressive strength. Lastly, the decomposition of the carbonate species (which produces free calcium and magnesium) was further studied. Indeed, the free alkaline earth cations led to structural modification in the alkali-activated samples.

Keywords

Callovo-Oxfordian, argillite, alkali-activated, heat treatment, carbonate, calcium

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