Consistency Characteristics and Behaviors of Eggshell Powder Stabilized Black Cotton Soil on Basement Complex of Part of South-Western Nigeria.

Expansive soils are one of those kinds of soils whose volume change takes place while it comes in contact with water. Therefore, prior to construction of a road on such sub-grade, it is important either to remove the existing soil and replace it with a non-expansive soil or to improve the engineering properties of the existing soil by stabilization using additives which are sourced locally. The black cotton (expansive) soil was obtained from a borrow pit on the basement complex at Igbo-Ora in Oyo State, South-Western Nigeria. The borrow site lies within the coordinates Longitude 7⁰24'45" and latitude 3⁰18'34". The black cotton soils used in the study were collected from depths between 0.3-1.0m below ground level. The eggshell wastes were taken from Obasanjo Farms, Ota, Ogun State, Nigeria. The eggshells were milled into powder and then substituted for black cotton soil from 0% to 30% at 10% intervals while 0% eggshell powder substitution served as control experiment. In line with BS 1377 (1990) and other relevant codes, consistency tests were conducted on the composite materials of black cotton (on basement complex) mixed with varying degrees of eggshell powder for the determination of liquid limit, plastic limit, shrinkage limit, etc. It is evidently clear from the results that the percentage shrinkage limit became constant at 30% eggshell powder substitution in black cotton soil on basement complex which is an indication of constancy of volume. [ABSTRACT FROM AUTHOR]