Microanalysis and Compactive Efforts Study of Black Cotton Soil Treated With Cement Kiln Dust

Abstract

An expansive clay, also known as Black cotton soil (BCS) was treated with up to 10 % cement kiln dust (CKD) using three different compactive efforts; British Standard light (BSL), West African Standard (WAS) and British Standard heavy (BSH) energies. Laboratory tests were performed on the natural soil and CKD treated soil samples in accordance with BS 1377 (1990) and BS 1924 (1990) respectively with the aim of improving the deficient soil to meet engineering requirements. Preliminary evaluations on the natural black cotton soil showed that it fell under A-7-6 (16) using AASHTO classification and CL according to Unified Soil Classification System (USCS). Results of laboratory tests carried out on soil specimens show that the properties of the soil generally improved with CKD treatment. Peak unconfined compressive strength (UCS) values of 357.07, 382.49 and 528.82 kN/m2 and California bearing ratio (CBR) of 7, 10 and 19 % as well as resistance to loss in strength of 44, 55 and 55 % were recorded at 10 % CKD treatment, respectively, for BSL, WAS and BSH compactive energies. Reduction in the particle sizes with curing period was observed when samples were viewed through the scanning electron microscope (SEM). The study showed that CKD can be beneficially used to improve the subgrade of lightly trafficked roads and as admixture in lime stabilization during construction of flexible pavements over expansive soil.Keywords: California bearing ratio; Cement kiln dust, Durability; Expansive soil; Microanalysis, Unconfined compressive strength; Scanning electron microscope.