Interfacial transition zone (ITZ) is the weakest part in concrete structure because of the interrelation between its special characters and the performance of concrete, and adding mineral admixture in concrete is a feasible and effective way to improve ITZ. The workability, mechanical and durability performance of filling materials with Fly ash and Coal gangue has been invesitgated, and the interrelation has been research in a micro view by means of SEM and EDS.