Clay Mineral and Soil-Structure

Types of Clay Minerals:-

1) kaolinite

2) illiite

3) Montmorillonite

Kaolinite

it is a clay mineral which is formed by one Gibbsite and one Silica sheet.

Thickness of one kaolinite unit is 7 Angstrom .

Severals structural units are joint together by strong hydrogen bond.

Since the strong bond is present between the different units hence Kaolinite is least active among all clay minerals.

Soil containing Kaolinite minerals shows no/very less swelling and shrinkage index characterstics.

eg.China soil.

It is found in old deposits.

No isomorphous substitutions takes place

Illite

it is a clay minerals containing two silica sheet and one Gibbsite sheet.

Thickness of one Illite unit is 10 A .

Several structural units are joint together by a ionic bond(potassium or sodium bond).

It is medium active clay minera.

Soil containg it shows medium activity means show intermediate shrinkage and swelling characterstics.

Montmorillonite 

it is a clay mineral containing two silica and one Gibbsite sheet.

Thickness of each unit is 10A.

Several structural units are joint together by Weak vander waal forces.

Since montmorillonite consists of weak forces between different unit hence ,it is most active clay mineral.

Soil containing it shows large swelling and shrinkage characterstics .

eg. Black cotton soil and Bentonite soil.