Modeling of moisture migration in an FRP reinforced masonry structure

The study of moisture migration in a layered structure made of distinct building materials is of great importance for the understanding of its hygrothermomechanical response and for the design consideration of long-term structural integrity and durability. Modeling of moisture migration in an fiber reinforced polymer (FRP) composite upgraded masonry structure is particularly necessary, since the interfacial adhesive between the reinforcing FRP laminate and the host masonry can be susceptible to moisture damages. In this study, a generic theoretical formulation based on the framework of the Fourier moisture diffusion model was developed for a layered structure. The resulting governing equation was expressed in terms of humidity potential state variable whose relation with the moisture content state variable of the constituent material was defined in the sorption isotherm material property. Finite element implementation of the humidity potential formulation was also carried out. The finite element humidity migration modeling scheme was then utilized to perform two case studies. It was shown that the moisture migration processes in a concrete slab with a reinforcing FRP laminate partially covering one surface as well as in an FRP reinforced URM unit with air cavity can be captured in details when these structures are subjected to outdoor/indoor isothermal humidity gradients.