Effect of adding cement kiln dust on the effective geotechnical properties of sand dunes in Najran–Sharourah, Kingdom of Saudi Arabia: a laboratory study

Sand dunes are one of the most common soil types all over the world, particularly in North Africa and the Arabian Peninsula. These dunes, with their regional extensions, are considered the main natural resource for fine aggregates being used in construction purposes. To use dune sands as a road construction material, suitable treatment is necessary. Sand dunes have typically been stabilized using a cement material, however, though extremely costly and consuming a substantial amount of energy, it is not particularly effective. Therefore, this study has investigated the potentiality of adding cement kiln dust (CKD) for enhancing the strength and durability of dune sands in Najran–Sharourah, SW Saudi Arabia. Twenty-seven specimens have been mixed with 0%, 10%, 20%, and 30% CKD plus 2% cement and then examined and assessed using macro-characterization techniques. Results indicated that the strength of the sand dune samples, treated with an enhanced mixture of 30% CKD and 2% cement, improved the minimum dry density from 1.652 at 0% to 1.854 g/cm3. The soil became more qualified as a construction material. This enhanced mixture can serve as a high-quality sub-base for both flexible and rigid pavements. Besides, micro-characterization techniques, including X-ray diffraction (XRD), back-scattered electron imaging (BEI), and scanning electron microscopy (SEM) supported by energy-dispersive X-ray (EDX), were applied to identify the various phases of the treated dune sands. Finally, the implementation of adding the CKD to the dune sands geomechanical parameters has been modeled, and a series of highly reliable mathematical equations have been introduced (0.938 ≤ R2 ≤ 1.0).