The interface plays an important role in the macro-mechanical properties of SFRC (Steel Fiber Reinforced Concrete)

especially the interface layer between the steel fiber and concrete matrix.The pull-out numerical models with or without aggregates have been established

then the effect of matrix strength on pullout properties of single fiber and the influence of aggregate have been studied. The results indicate that the higher the matrix strength

the larger the peak load of specimen and the higher the interfacial bond strength

but the pull-out toughness decreases. The variation of matrix strength has little impact upon the damage process of pullout procedure. The specimen with concrete matrix is more sensitive to the changes of matrix strength compared with cement.