Title: Comparison of strength and mechanisms of stabilized samples of coarse and fine-grained soils with cement kiln dust

Abstract

Road pavement soils have not had sufficient resistance in most road construction projects. Therefore, instead of substituting high-strength soils for base soils, cement kiln dust like stabilizers can be used that are not only inexpensive but also environmentally friendly. In this research, stabilization of coarse-grained sandy soils (SP) and silty fine-grained soils (SM) using different percentages of 5, 10, 15 and 20% of cement kiln dust has been investigated. Standard compaction and uniaxial compressive strength tests as well as direct shear test with two types of soil mentioned with different percentages of cement kiln dust at the time of curing and 7, 14 and 28 days have been performed. The results show that by adding 20% of CKD to sandy soil, the resistance has increased 11.3 times than of the base soil, while with the same percentage of CKD, the uniaxial strength of silty soil has increased by 9.8. Therefore, the CKD stabilizer for coarse-grained sands has a greater effect than fine-grained, which can be attributed to the better locking of sand grains in the effect of increasing the CKD than silty soil. Also, microstructural experiments including XRD, SEM, EDAX, FTIR have been performed for stabilized samples and base soil and the results have shown that changes in the peak Formation of CSH gels and coherent structure related to sandy soil have been observed that confirms this issues.