Abstract: This paper aims at the performance of concrete mortar casted at layer interface by testing tensile splitting strength, ultrasonic pulse, rapid chloride permeability, water permeability, among others. We perform different tests for different intervals between the casting times of upper and lower layers to achieve a better evaluation of the influence of layer interface on the properties of concrete, and observe the microstructure of the layer interface under a scanning electron microscope. The results show that as the casting interval increases, tensile splitting strength and the ultrasonic wave amplitude of first arrival are decreased, but initial electric current and permeability coefficient are increased. The seepage in composite specimens follows the linear Darcy’s model, while in bulk specimens it follows a non-linear model with starting pressure gradient as an additional factor. A very good relationship exists between tensile splitting strength and the amplitude of first arrival. The structures of layer interface are quite different before and after the initial setting time of mortar. When the casting interval is shorter than the initial setting time, hydration products around the interface are almost the same as cement paste, while for long intervals, many interconnected voids and micro-cracks assemble around the interface.