Experimental investigation on properties of interface between concrete layers

The integration and permeability of the interface between concrete layers of a dam considerably affect its structural functionality and safety. To understand the interface properties, several tests were conducted to examine the various characteristics of specimens with different layer interfaces. The mechanical property in terms of bond strength was assessed using the splitting tensile test, which was affected by interval time. On the other hand, the ultrasonic pulse test was used to confirm the influence of the interface on ultrasonic attenuation. The chloride and water permeability were also investigated by means of the rapid chloride permeability, alternating current resistance, and water permeability tests. The results of these tests proved that longer interval times lead to a weaker bond strength and higher permeability, which are harmful to layer structures. The change rules of mechanical and permeability properties were confirmed by the optical micrograph and hardness distribution of the overlay transition zone. Finally, the relationships among these tests were analyzed, and strong correlations demonstrated that the non-destructive ultrasonic pulse test and rapid electrical test could be employed to predict and evaluate the bond strength and permeability of a layered interface.