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Geochemistry and predictability of tropical clay behaviour using different techniques


Due to complications in describing and analysing the behaviour of earth materials resulting from alteration of rocks, detailed laboratory and empirical studies of their geochemical, geological, and mechanical properties are very essential and require great attention. In this work, geochemical indices have been used as an important tool in characterising tropical clays and mechanical behaviour has been predicted using different techniques. This was achieved by using a scanning electron microscope equipped with an electron dispersive spectrometer and conducting statistical analysis on tropical clays, materials that are frequently encountered by practising engineers. The mechanical behaviour considered were inherent (in situ specific volume), compression (compression index and intercept), and strength (uniaxial compressive strength), and the indices used were physical (e.g. fines content), mineralogical (e.g. quartz), and chemical indices (e.g. silica-to-alumina ratio). Tropical clay can be characterised by relating chemical indices with both depth and in situ specific volume, and the most appropriate chemical indices are alumina-titania index (ATI), silica-titania index (STI), and silica-to-alumina ratio (SA). The in situ specific volume will be satisfactorily predicted by the coefficient of uniformity (Cu), ATI, STI, and SA. The fines content (Fc), Cu, quartz, and the SA are the most suitable predictor for the compression behaviour. The strength will be successfully predicted by Fc. Physical, mineralogical, and chemical indices can be used to predict mechanical behaviour, and they are recommended for practitioners working on these materials depending on the properties required.

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modified from Okewale 2020b)

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Fig. 11



Alumina-titania index


Compression index


Clay fraction


Chemical index of alteration


Chemical index of weathering



C u :

Coefficient of uniformity

D 50 :

Mean particle size


Fines content




Plasticity index


Leaching coefficient


Liquid limit


NCL intercept at 1 kPa


Weathering product index


Plagioclase index of alteration


Plastic limit




Residual coefficient


Silica-to-alumina ratio


Silica-titania index


Uniaxial compressive strength

v :

In situ specific volume


Vogt’s residual index


Weathering index of Parker


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The authors would like to thank the National Research Foundation (NRF) of South Africa for the award of fellowship which led to this paper. The authors would like to appreciate Mr Akerele C. for his assistance in the laboratory in the course of conducting this research. Special thanks to Prof. Mohamed Th. S. Heikal, Prof. of Mineralogy and Petrology, Tanta University, Egypt, for his critical comments and suggestions that strongly improved the present article.

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Correspondence to Ismail Adeniyi Okewale.

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Okewale, I.A., Grobler, H. Geochemistry and predictability of tropical clay behaviour using different techniques. Arab J Geosci 14, 2209 (2021).

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  • Mineral chemistry
  • Mechanical parameters
  • Tropical clay
  • Statistics