Cement stabilization is a practical improvement method of the soil bearing capacity of problematic soils. Soil bearing capacity is attributed to its strength and durability. The decrease in durability can be caused by weathering. On this account, to improve the long-term behavior of soil experiencing weathering process, it is necessary to apply cement stabilization to ensure the quality of road performance. This paper presents the results of a laboratory investigation on slaking index and the physical change of cementstabilized soil. A new sample preparation method of stabilized soil is presented in this study for the slakedurability test. The cement content was varied from 2 to 10 percent of the dry soil. The test results show that the unstabilized compacted-siltstone was ruined on the first test cycle. In general, the degree of slaking (Is) increases with the slaking cycle but decreases with the cement content. Whereas, the slaking durability index (Id(2)) increases as cement content increases. A large quantity of cement was required to obtain a successful stabilization. This study recommends that 7% of cement is suitable for soil modification, while 10% of cement satisfies the requirement for stabilization.