Hydraulic conductivity of modified clay treated with CKD

Abstract

This paper presents the results of a laboratory evaluation of hydraulic conductivity k of black cotton soil modified with 10% quarry fines and treated with 0, 4, 8, 12 and 16% cement kiln dust (CKD) with reference to the use of the composite as landfill liner. Physical characterisation and k tests were conducted on untreated and treated soil mixtures. Specimens for the k test were prepared at moulding water contents of −2, 0, +2 and +4% of optimum water content and compacted using the British Standard light effort. Permeation with water was carried out after curing specimens for 7 and 28 d using the falling head test system. Results show that treated soil mixtures exhibited a decrease in k when moulding water content increased from 2% dry to 2% wet of optimum, but a subsequent increase in moulding water content to 4% wet of optimum caused an increase in k. The k of treated soil mixtures decreased, on average, by a factor of 3 for specimens prepared at CKD = 4% and by three orders of magnitude for CKD = 16% relative to the untreated condition. Furthermore, there was a significant difference between k values for 7 and 28 d cured specimens.