Experimental investigation on using Cement Kiln Dust (CKD) as a cement replacement material in producing modified cement mortar

•Cement Kiln Dust incorporation led to decrease both strength and flow.•Cement Kiln Dust can be used as a cement replacement material.•Fractal dimension can be used to evaluate the CKD mortars.•Image analysis technique can be utilized in mortar quality assessment.

Concrete is regarded as the second consumed construction material and hence massive quantities of cement needs to be annually produced. This production leads to pollute the environment by releasing significant quantities of CO2 emission in addition to produce solid waste material known Cement Kiln Dust CKD. The aim of this investigation is to explore the possibility of using this material as a cement replacement in concrete mortar production, which occupies about half of the concrete volume. Chemical analysis and some physical properties of three different CKD replacements (10%, 20%, and 30% wt. of cement) in addition to reference mortar were investigated. The results showed that there is a systematic increase in mortar porosity with CKD replacement and this increase was in parallel decrease in mortar strength. Image processing was utilized to study the mortars in terms of 2-D porosity and cement paste color values. It was found that the calculated porosity using imageJ software also increased with CKD replacement and the pore-size distribution can be counted as fractal object, where the fractal dimension of these pores was calculated. Additionally, a good correlation between gray color value and compressive strength was also concluded.