Fly ash (FA) is widely used in construction industry as a pozzolanic material for its economic and environmental advantages. However,the variety and the complexity of the chemical composition of FA make it difficult to control the quality in engineering practice. Especially the durability of FA concrete has to be considered in the design. This durability is strongly influenced by the internal chemistry and the microstructure of cement paste. The aim of this article is to present a review on the effect of FA on the durability of concrete with particularly focus on the hydration chemistry and the development of microstructure. Meanwhile,existing hydration models for hydration kinetics and microstructure development of concrete blended with FA is discussed. The results of this research will provide a modelling perspective for predicting durability of concrete when FA is used as a blending material in the mixtures. However, the variety and the complexity of the chemical composition of FA make it difficult to control the quality in engineering practice. Especially the durability of This durability is strongly influenced by the internal chemistry and the microstructure of cement paste. The aim of this article is to present a review on the effect of FA on the durability of concrete with particularly focus on the hydration chemistry and the development of microstructure. Meanwhile, existing hydration models for hydration kinetics and microstructure development of concrete blended with FA is discussed. The results of this research will provide a modeling perspective for predicting durability of concrete when FA is used as a blending material in the mixtures.