Characterisation of calcined raw clays suitable as supplementary cementitious materials
By Tobias Danner, G. Norden, H. Justnes. Applied Clay Science, 2018
147 citations recorded by the source corpus.
Abstract The potential use of two raw clays (Clay A: kaolin; Clay B: calcareous montmorillonite) as supplementary cementitious material (SCM) in blended cements was investigated. Cement replacement in mortars by 20% calcined Clay A and Clay B resulted in a considerable 28 day compressive strength improvement. The pozzolanic reactivity of Clay A and B is explained by characterisation of the structural changes upon calcination with XRD, ICP-MS, FT-IR, 27Al NMR, Mossbauer spectroscopy and SEM. At the temperature giving highest pozzolanic reactivity, kaolinite and montmorillonite were completely dehydroxylated, while calcite from Clay B was not completely decomposed. FT-IR, 27Al NMR and Mossbauer spectroscopy revealed considerable structural deformations of kaolinite in Clay A and montmorillonite in Clay B resulting in an amorphous, reactive state. Oxidation of iron in Clay B during calcination contributed to strong distortions of the octahedral sheet in the montmorillonite structure. Additionally, the formation of a glass phase due to reaction of coccoliths (CaCO3) and montmorillonite was observed.
Subfields: Biomaterials, Building and Construction, Civil and Structural Engineering
View Paper: https://www.semanticscholar.org/paper/36a05e1687d8d16aa3b603e2aad222debf83b976
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Citations in the corpus
- Calcined clay – Limestone cements: Hydration processes with high and low-grade kaolinite clays (2021, background): “Such results on binary binders containing low-grade kaolinitic or natural calcined clays are very promising and encouraging ([18], [22], [23]).”