Precast concrete components are often designed to receive a structural or non-structural in-situ concrete overlay. The most common examples are precast slab systems that combine the advantages of prefabrication with an increase in member stiffness and load bearing capacity resulting from the cast-in-place concrete. The structural performance of such composite members depends largely on the shear resistance provided at the interface. This paper provides an overview on factors affecting the bond strength of unreinforced interfaces between precast components and in-situ overlays. Following publications in this series of 3 papers will address the issues of differential volume changes, as well as structural properties and applications of composite precast to in-situ concrete members.