Pozzolanic reactivity of a calcined interstratified illite/smectite (70/30) clay
Calcined clays can be potential supplementary cementitious materials if effects of heat-treatment on their structure and reactivity are understood. This work reports structural characterization of an interstratified illite/smectite clay, including a quartz impurity, upon heating using {sup 27}Al and {sup 29}Si MAS NMR spectroscopy and ICP-OES analysis. During dehydroxylation (600–900 °C) the Q{sup 3}-type SiO{sub 4} sites become disordered and octahedral AlO{sub 6} sites transform into tetrahedral sites, resulting in an amorphous material with substantial pozzolanic properties, as demonstrated by reactivity tests and hydration studies of a Portland cement–calcined clay blend. At higher temperatures (above 950 °C), inert Q{sup 4}-type phases crystallize which radically reduce the reactivity. At optimum calcination temperature (900 °C), the amorphous material contains highly dissolvable elemental species as seen from complementary ICP-OES analysis. The quartz impurity exhibits a unique variation in {sup 29}Si spin–lattice relaxation times upon heat-treatment which is ascribed to changes in the concentration of impurity ions in quartz.
- OSTI ID:
- 22696537
- Journal Information:
- Cement and Concrete Research, Vol. 79; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
- Country of Publication:
- United States
- Language:
- English
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