Moisture Degradation in Concrete/epoxy Systems

Combining several materials to create a structural system has led to a new kind of application previously not possible with conventional materials. Examples are FRP and its strengthening system. Nonetheless, the existence of the interface between two substrates introduces a challenging problem in determining durability of bond systems. In many applications, the durability of individual materials is well-documented. However, the property of the interface can significantly deviate from the constituents and special attention is required. This is because of the different structure at the interface resulted from chemical reaction between the substrates to generate adhesion force as suggested by many studies at microscopic level [1-3]. Concrete/epoxy interfaces are formed when advanced composite materials are applied to strengthen or repair civil infrastructures. One of the most common applications is the retrofitted FRPbonded concrete. The structural performance of such applications is usually governed by the concrete/epoxy interface [4-6]. Therefore, quantification of concrete/epoxy interface is essential to prevent the pre-mature failure at such interface. Based on the prior research studies, it is found that the concrete/epoxy interface is the most critical region when subjected to moisture [7]. Hence, this study focuses on the experimental characterization of concrete/epoxy interfaces with the effect of moisture. In order to understand the durability and fundamental debonding mechanisms of FRP-bonded concrete systems, experimental studies using a fracture-based approach have been conducted. In the experiments, concrete/epoxy systems were tested under mode-I and mixed mode loading. Fracture-based tests aims to determine the fracture toughness (Γ) required to produce the debonding failure of a concrete/epoxy interface. In what follows, we introduce the sandwich model for fracture characterization of the interface of concrete/epoxy system. This will be followed by the description of the specimens used in characterizing the fracture toughness properties of concrete/epoxy interface for the investigation of fracture toughness trends at such interface.