Recently, Ground Granulated Blast Furnace (i.e. slag) blended cement has been specified to be used for many mega national projects due to its low heat of hydration and expected durable behavior. Accordingly, demand for high quality locally produced slag cement has increased. On the other hand, improving the durability performance of the proposed local slag cement is essentially required to be used under different severe exposure conditions. Therefore, adequate durability performance study of cementitious materials made of locally blended slag cement is required before and after proposed pozzolanic partial replacement. In this research work, the durability performance of different cementitious materials, made of two different brands of locally produced slag blended cements (i.e. CEM III/A-42.5N), is assessed. On the other hand, the same durability assessment process was applied for cementitious materials made with one of the slag cement brands after partial weight replacement with various pozzolanic materials (i.e. 20% fly ash and 10% silica fume). Similarly, durability performance was assessed for cementitious materials made with CEMI-42.5 partially replaced with 50% of fine grounded glassy blast-furnace slag. Based on the test results, local brand CEM III/A-42.5N, partially replaced with 10% silica fume, provided the best durability enhancement compared to the other investigated blended cements. This paper is intended to provide guidance for those concerned with specification, application and performance of concrete under severe exposure conditions (e.g. marine applications).