hi...in ABAQUS there is a surface to surface contact element available, use this element to simulate the bond b/w steel and concrete..the contact element properties are define in terms of normal stiffness i.e. normal to the contact surface another parameter called shear stiffness i.e. tangential friction force b/w two surface..I suggest you read ABAQUS manual to know more in details about this element ..ok all the best in your research..

For embedded reinforcement you don't need to model the bond between reinforcement and concrete. Surface to Surface element connection should work fine. Please try to find a way to declare the reinforcement as an embedded one.