A Review of Bonding Performance at the Interface between New and Old Concrete

Abstract

The bonding interface between existing and new concrete is critical in construction and renovation projects, as its strength directly determines the structural performance. This paper provides a critical review of factors affecting this interfacial bond, focusing on four key aspects: substrate roughness, interface agents, concrete strength, and the use of dowel bars. The analysis indicates that surface roughening significantly enhances bond strength, with an optimal critical roughness beyond which the improvement plateaus. Furthermore, epoxy-based interface agents are more effective than cement paste in improving the tensile strength of the interface. While the strength of both concretes is important, increasing the strength of the new concrete has a more pronounced effect on the overall bond performance. Finally, the incorporation of dowel bars alters the failure mode from brittle to ductile through a composite action, thereby enhancing the safety and reliability of the bonded interface.