Presence of alkaline elements such as sodium and potassium are highly detrimental for blast furnace operations. Even a trace amount of alkali affects the performance of raw materials considerably. The performance of coke in the process suffers significantly in presence of alkalis by the catalysis of Boudouard reaction during its descent through the shaft and subsequent deterioration of its strength in the lower zone of the furnace, leading to various furnace operating problems. The aim of this work is to investigate the impact of these harmful elements on the coke structure in micro as well as nano level. The Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) values of coke are determined for original industrial coke samples as well as the same samples artificially impregnated with alkaline elements in different amounts. The original and CRI-method treated samples (with and without added alkali) are characterized using Scanning Electron Microscopy (SEM), X-Ray Diffractometry (XRD) and Transmission Electron Microscopy (TEM) to look into the lattice and crystalline structure of the constituent graphite of coke. The results demonstrate pronounced disturbance in the graphite lattice caused by alkali. An attempt has been made to explain the mechanism of the deterioration of coke properties under the influence of alkalis in terms of the difference in atomic radii of the constituent elements.