ABSTRACT: Aggregate has widely used in concrete composition and its properties directly affects the durabilityof concrete. Geological factors such as aggregate type, mineralogy and texture have significant effects onconcrete strength and durability. In this study, granitic rocks collected from different parts of Turkey, havebeen investigated from the point of alkali-silica reactions in concrete. Firstly, mineralogical, petrographicand chemical characteristics of granitic rocks were investigated. Then, accelerated mortar bar testswere performed on these granite samples. The effects of alkali-silica reactions were also investigatedby scanning electron microscope (SEM). According to results obtained, granites, when used as concreteaggregate, are not generally found to be potentially dangerous for alkali-silica reactions.