Push-out test to study bond properties of mortar–concrete interface

Post-installed grouted anchors have been applied widely in anchorages to concrete. The efficiency of the load transfer mechanism much depends on the bond strengths of both the anchor–mortar and mortar–concrete interfaces. However, no standardised test method is currently available for bond properties at the mortar–concrete interface. The intention of this paper is to provide a rational test approach for analysing the interfacial behaviour between mortar and concrete in the anchor–mortar–concrete anchorage system. A modified push-out test was conducted with local support at the unloaded end to avoid radial cracking of concrete block during the process of mortar push-out. Nine sets of specimens were tested with three different mortar cylinder diameters and three different bond lengths. The local bond–slip relationship was approximately obtained from push-out specimens with the shortest bond length. The bond strength was found to decrease with an increase in mortar specimen size. Furthermore, a mathematical model is proposed to predict the maximum push-out loads for different bond lengths using the obtained bond parameters. The validity of the proposed test method is verified by comparing analytically predicted and experimental peak loads.