In the previous post we have discussed many topics about properties of black cotton soil and foundation considerations of these type of soils. Some of these become popular to reader as they have several thousands of viewers in a month. This is a great achievement to us. You can read all these posts by following the link “black cotton soil”. In some posts we have provided some reinforcing methods for black cotton soils. Now in this post we will learn about a form of chemical treatment with calcium. To have better understanding you can first read “Molecular Sandwich of Black Cotton Soil”.
Chemical treatment is used to change the mineral structure of clay and thus reduction in its expansion potential. For this purpose calcium oxide treatment is the oldest method to treat black cotton soil. Calcium oxide is nothing but lime and with the presence of water it changes the properties of black cotton soil.
Here we are trying to list the actions that are taken by lime and subsequent response of black cotton soil against these actions-
a. Lime produce a cation exchange reaction where ions are exchanged
b. In the solution the atoms with positive charge are substituted to opposite form of ions of crystal of clay minerals.
c. Smaller clay particles becomes large one by flocculation-agglomeration process
d. Mineral structure changed by the reaction of particles having positive ions with negative one.
e. Cementing agents are formed in expansive soil
f. With the above alteration of soil properties the swelling and shrinkage potential get minimized to some extent not to generate any foundation problems.
Thus the resulting treated black cotton soil becomes a strong, firm and less expandable good grounding bed for placing foundation.