Several methods are available for measuring the oxygen diffusion coefficient of polymer materials. However, as they were developed for the food packaging industry they can only be used where the material thickness is very small. As such they are unsuitable for obtaining the oxygen diffusion properties of the much thicker systems used in infrastructure applications where epoxy or FRP is bonded to concrete elements. This paper provides details of a new system and its application to determine the oxygen permeation constants for materials used in infrastructure repair.
Chloride-induced corrosion of steel in concrete requires the presence of oxygen and moisture for the electro-chemical reactions responsible for corrosion to continue. Repair of corrosion-damage often utilizes polymers such as epoxies or more recently, fiber reinforced polymers (FRP) Sheikh et al., 1997; Debaiky et al., 2002; Sen 2003. The durability of the repair depends on the extent to which FRP or epoxy can prevent the entry of deleterious materials such as moisture and oxygen that allow the electro-chemical reactions to be sustained. As the size of the oxygen molecule is smaller than that of the water or chloride molecule and its interactions with epoxy weaker, its diffusion characterization is the most significant. This is because the larger the molecular diameter and stronger the interactions the smaller the diffusion coefficient. For this reason, oxygen can diffuse faster than both chlorides and water. The new diffusion cell can also be used to evaluate the effectiveness of FRP-concrete systems used in corrosion repair. The new diffusion cell was successfully used to determine oxygen permeation characteristics of epoxy (Khoe et al. 2010), FRP (Khoe et al. 2011a) and FRP-concrete systems (Khoe 2011). This paper provides background information on the development of the new system and its application for materials used for infrastructure repair.