The expansion potential of Black cotton soil is the combined influence of clay particle type and its quantity in the soil. Clay particles which cause a soil to be expansive are extremely small. Their shape is determined by the arrangement of their constituent atoms which form thin clay crystals.
The principal elements in clay are silicone, aluminum and oxygen. Silicone atoms are positioned in the center of a pyramid structure called a tetrahedron with one oxygen atom occupying each of the four corners. Aluminum atoms are situated in the center of an octahedron with an oxygen atom occupying each of the eight corners.
|Octahedral sheet is sandwiched between two tetrahedral sheets to create the mineral structure of Black Cotton soil|
Silicon Tetrahedral sheets are formed sharing electron in Black Cotton Soil
There are many other elements which can become incorporated into the clay mineral structure Black cotton soil such as hydrogen, sodium, calcium, magnesium, sulfur, etc. The presence and abundance of various dissolved elements or “ions” can impact the composition and behavior of the clay minerals.
One octahedral sheet is sandwiched between two tetrahedral sheets
to create the mineral structure. In Black cotton soil, groupings of the
constituent clay crystals will attract and hold water molecules between their
crystalline sheets in a sort of “molecular sandwich”.
Aluminum octahedral sheets are formed sharing electron in Black Cotton Soil