Abstract: Prestressed concrete has been used all over the world for bridge construction, but severe corrosion of steel strand in post-tensioned tendons has been documented. Recently, the corrosion was associated with physically and chemically deficient segregated grout with elevated moisture and concentrations of aggressive chemical species that allowed for early aggressive corrosion to develop. The transport of moisture and ionic species was thought to be related to capillary transport through the braided steel wires, but other transport mechanisms within the tendon duct may be possible as well. The grout mass pressure within the grout column increases the hydrostatic pressure in the system. Vertical elevation of the grout with the hydrostatic pressure of grout mass may elevate the moisture content at higher elevations. The paper reviews the results of lab and field testing characterizing deficient grouts and the various transport mechanisms that can be formed in post-tensioned tendons, including modeling efforts of unsaturated flow and solute transport using HYDRUS-1D.