SORPTION AND DIFFUSION OF WATER, SALT-WATER, AND CONCRETE PORE SOLUTION IN COMPOSITE MATRICES

In recent years, the use of fiber-reinforced polymer composites in civ il infrastructure has been promoted as a solution to the deterioration of bridges, buildings, and other structures composed of traditional m aterials, such as steel, concrete, and wood. Any application of a poly mer composite in an outdoor environment invariably involves exposure t o moisture. There is also potential for exposure to saline conditions in waterfront or offshore structures, and alkaline environments, as wo uld be encountered by a reinforcing bar in a cementitious material. Th is study characterizes the sorption and transport of distilled water, salt solution, and a simulated concrete pore solution in free films of vinyl ester, isophthalic polyester (isopolyester) and epoxy resins, a ll commercially important materials for use in structural composites. Diffusion of all three liquids in each of the three materials was obse rved to follow a Fickian process. Mass loss was observed for the isopo lyester in salt water and concrete pore solution at 60 degrees C, sugg esting hydrolysis that was accelerated by the high temperature exposur e. Both the rate of uptake, as well as the equilibrium uptake, were gr eater at 60 degrees C, compared with ambient conditions. Diffusion coe fficients calculated from the mass uptake data revealed that, although the epoxy resin had the highest equilibrium uptake, it had the lowest diffusion coefficient. (C) 1999 John Wiley & Sons, Inc.