Abstract: Interaction mechanism between very early-age concrete and structures is very complicated, as it is effected by composition of concrete, behavior of structure surface, setting time of concrete, demoulding velocity, and lubricating condition. In this study, we have designed and conducted model tests for the measurements of tangential force at the interface of concrete and formwork in different conditions and analyzed the test data. The experimental results showed that the tangential force had two components, i.e. frictional force and bonding force, and at initial stage it largely came from the bonding effect of cement mortar. Its correlation with time became stronger as water-cement ratio decreased, while along with concrete setting, it increased significantly and the correlation also slightly increased. Demoulding velocity had little influence on this force, while lubricant could help to decrease it at initial stage and keep it steady in mid-late stages. To interpret the experimental results, we developed a micromechanical model for the interaction mechanism between concrete and structures.