Dear Mr. Oluwatuyi,

kaolinite is the most common phyllosilicate as the pH drops into acidic territory.  The other way round if you add, e.g.,  KOH to an aquatic system you may see the kaolinite disappearing from the chemical system.  A change into gibbsite common to laterites may be achieved when the activity of SiO2 (aq) is lowered. During this desilicification process a more or less stable pH value can be maintained. The pH range lies between 3 and 14. White mica which is stable at a pH level higher than kaolinite at approx. 6 to 7 may responds in the same way to a lowering of the activity of SiO2 (aq). You can also slightly modify the chemical system by changing the activity of the dissolved species such as K+. This is a rough scheme to approximate the chemical changes near the boundary between the argillaceous parts and encrustations of laterites.

Best regards

H.G.Dill

Dear H.G.Dill

Thank you Sir for your response, assuming that the chemical system was actually modified (which am not certain of). Is it possible for kaolinite to be absent in a chemical system and be present in another when all the conditions (except the addition of binder) were the same? Will the addition of binder (lime and cement) alter the chemical system of a lateritic soil?

Kind Regards

Dear Mr. Oluwatuyi,

To say it frankly, I am not involved in this project to the extent that I can draw more far-reaching conclusions at the moment. It am reluctant to speculate on systems and provide you with a "dead-end road". This would not be helpful for you.

I wish you much success

H.G.Dill

Hi all, 

In my view it is unlikely for a mineral phase such as kaolinite to disappear and then reappear at constant pH and room temperature simply by addition of lime-cement binder. It might be beneficial to think about possibility of surface modification of Kaolinite and Illite particles (formation of new and relatively thick layer of secondary minerals on the surface of these particles upon binder addition).

Kind regards,

Ata

 Thank you so much Sirs (Harald G.Dill and Ataollah Nosrati)

If I may ask Ata. In the case of surface modification of Kaolinite and Illite mineral particles, will the X-ray Diffractometer still detect them as Kaolinite and Illite?

You are welcome Opeyemi,

Regarding your question about the XRD detection capability, unfortunately I don't have enough knowledge about XRD to say what can be maximum penetration depth (for single particles) in analysing solid samples. This being said, in my view it is highly likely that some mineral phases/particles not to be detected (or identified correctly) if their surface is covered by thick layer of another/secondary mineral or precipitate (e.g., calcium sulphate). I suggest you ask this question from those who are experts in XRD analysis.

Kind regards,

Ata

Dear Opeyemi, kaolinite particles or "booklets" coated by iron oxyhydroxides (e.g., goethite, or hematite) in lateritic crusts (e.g., ferricretes) are generally detected by Xray diffraction of homogenized powder fractions (see papers in my research gate pages). Illite can also be detected if proportion is over 5 w.% of the total weight of the sample analyzed. Best wishes, Anicet