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Open AccessFeature PaperArticle

Effect of Alkali Concentration on the Activation of Carbonate-High Illite Clay

Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari Aldo Moro, 70121 Bari, Italy
Instituto Eduardo Torroja (CSIC), 28033 Madrid, Spain
Authors to whom correspondence should be addressed.
Appl. Sci. 2020, 10(7), 2203; (registering DOI)
Received: 25 February 2020 / Revised: 13 March 2020 / Accepted: 16 March 2020 / Published: 25 March 2020
(This article belongs to the Special Issue Low Binder Concrete and Mortars)
The present study explores the effect of activating solution concentration (4, 6 and 8 M NaOH) on mechanically and thermally pre-treated carbonate-high illite clay (LCR). Pastes were prepared with an alkaline solution/clay (S/B) ratio of 0.55, which were cured at room temperature and relative humidity > 90% in a climatic chamber. At two and 28 days, compressive mechanical strength was determined, and the reaction products were characterised by X-ray Powder Diffraction analysis (XRPD), Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy - Energy Dispersive X-ray spectroscopy (SEM/EDX). Results obtained showed that the presence of reactive calcium in the starting clay induces co-precipitation of a mix of gels: An aluminium-enriched C-S-H gel (C-A-S-H) and a N-A-S-H gel, in which sodium is partially replaced by calcium (N,C)-A-S-H. Pastes prepared with higher (6 or 8 M) activator concentrations exhibit a more compact matrix than the ones prepared with 4 M NaOH. The findings show that the use of a 6 M NaOH solution yields a binder with two days compressive strength >20 MPa and 28 days strength of over 30 MPa. View Full-Text
Keywords: carbonate-high illite clay; alkali activation; NaOH; activator concentration carbonate-high illite clay; alkali activation; NaOH; activator concentration
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MDPI and ACS Style

D’Elia, A.; Pinto, D.; Eramo, G.; Laviano, R.; Palomo, A.; Fernández-Jiménez, A. Effect of Alkali Concentration on the Activation of Carbonate-High Illite Clay. Appl. Sci. 2020, 10, 2203.

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