Moisture-induced Debonding in Concrete-epoxy Interface

Concrete-epoxy interface can be found in many strengthened or retrofitted structures, especially in Hong Kong where concrete structures are the majority. In practice, epoxy is usually used in repairing concrete structures because of its excellent adhesion, chemical and heat resistance, good mechanical properties and electrical insulating properties. The bond between concrete and epoxy has been found to be strong enough such that failure does not occur at the interface under dry condition. However, prior research studies have indicated that moisture-affected debonding in a concrete-epoxy bonded system is a complex phenomenon that may often involve a distinctive dry-to-wet debonding mode shift from material decohesion (concrete delamination) to interface separation in which concrete-epoxy interface becomes the critical region of failure. Such premature failures may occur regardless of the durability of the individual constituent materials forming the bonded material systems. In this paper, a review on moisture degradation of concrete-epoxy interface is presented, followed by an explanation of such phenomenon using an atomistic approach which can fundamentally describe the interaction between the bonded system and the surrounding water molecules. It is highly recommended that the durability of concrete-epoxy interface should be carefully considered in the design stage due to the detrimental moisture effect.