Investigating the Influence of the Combination of Cement Kiln Dust and Fly Ash on Compaction and Strength Characteristics of High-Plasticity Clays

An experimental study was conducted to determine the effect of cement kiln dust (CKD) and fly ash (FA) on compaction and strength characteristics of the high-plasticity clay obtained from a forest road in North of Iran.  Accordingly, the soil was mixed with ۱۵% CKD by dry weight the soil, and a partial replacement of the CKD with ۱۰, ۲۰, and ۳۰% FA was applied to produce mixtures. The unconfined compressive strength tests were performed on specimens after a curing time ۷ and ۲۸ days. Also, the microstructures of untreated and treated specimens were examined using a scanning electron microscope (SEM). It was found that incorporation of CKD and FA leads to a decrease in the volume of pores in the soil matrix, which is due to the formation of calcium silicate hydrates and calcium aluminate hydrates gels. These cementitious compounds in the mixtures were presumed to be the significant factor contributing to strength improvements.