The assessment of pozzolanic activity is essential for estimating the reaction of a material as pozzolan and many studies have been performed to find a general test method that,besides being valid for every type of pozzolan,is acceptable for accuracy and quickness.A number of methods have been suggested for estimating pozzolanic activity. These can be subdivided into chemical and physical tests. In chemical tests, the amount of combined lime in a lime-pozzolan solution, or the amount of silica or silica and alumina soluble in an acid or alkali, has been used as an index of the pozzolanic activity. In physical tests, unconfined compressive strength has been used for assessing pozzolanic activity (Shi et al. 2006). Both the American Standards (ASTM) and British Standards (BS) defined indices that define the ratio between the compressive strength of a specified cement pozzolan mortar and a control mortar with plain cement. In the present research, the solubility of a natural pozzolan inboiling0.5MNaOH, which wasreported as arapid chemical test for evaluating pozzolanic reactivity by Milestone (1978), was used