Natural pozzolans, also known as trass, can be used in cement manufacturing due to their cementitious properties after reaction with calcium hydroxide. At different mixture proportions, the strength, setting time, workability, and soundness of the cement mortar made will differ. In this paper, cement mortars with six different natural pozzolan additions (ranging from 0 to 35%) were employed while using one type of natural pozzolan. As the experimental results show, increase in a natural pozzolan addition decreases the early age strength of cement significantly as expected and decreases the soundness of mortar by two-thirds. In addition, the workability conditions relatively improve and the settings delay for awhile.